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Found 435 entries in the Bibliography.
Showing entries from 351 through 400
| 2014 |
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Chorus acceleration of radiation belt relativistic electrons during March 2013 geomagnetic storm The recent launching of Van Allen probes provides an unprecedent opportunity to investigate variations of the radiation belt relativistic electrons. During the 17\textendash19 March 2013 storm, the Van Allen probes simultaneously detected strong chorus waves and substantial increases in fluxes of relativistic (2 - 4.5 MeV) electrons around L = 4.5. Chorus waves occurred within the lower band 0.1\textendash0.5fce (the electron equatorial gyrofrequency), with a peak spectral density \~10-4 nT2/Hz. Correspondingly, relativistic electron fluxes increased by a factor of 102\textendash103 during the recovery phase compared to the main phase levels. By means of a Gaussian fit to the observed chorus spectra, the drift and bounce-averaged diffusion coefficients are calculated and then used to solve a 2-D Fokker-Planck diffusion equation. Numerical simulations demonstrate that the lower-band chorus waves indeed produce such huge enhancements in relativistic electron fluxes within 15 h, fitting well with the observation. Xiao, Fuliang; Yang, Chang; He, Zhaoguo; Su, Zhenpeng; Zhou, Qinghua; He, Yihua; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; Baker, D.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2014 YEAR: 2014 DOI: 10.1002/2014JA019822 |
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RadFET Dosimeters in the Belt: the Van Allen Probes on Day 365 Van Allen Probes A and B, launched more than a year ago (in August 2012), carried 16 p-channel metal-oxide-semiconductor Radiation-sensitive Field Effect Transistors (RadFET)s into an orbit designed by NASA to probe the heart of the trapped-radiation belts. Nearly 350 days of in situ measurements from the Engineering Radiation Monitor (ERM) (1) demonstrated strong variations of dose rates with time, (2) revealed a critical correlation between the ERM RadFET dosimeters and the ERM Faraday cup data on charged particles, and (3) permitted the mapping of the belts by measuring variation with orbit altitude. This paper provides an update on early results given in a NSREC2012 paper along with details and discussion of the RadFET dosimetry data analyzed . Holmes-Siedle, A.G.; Maurer, R.; Peplowski, P.; Published by: IEEE Transactions on Nuclear Science Published on: 04/2014 |
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RadFET Dosimeters in the Belt: the Van Allen Probes on Day 365 Van Allen Probes A and B, launched more than a year ago (in August 2012), carried 16 p-channel metal-oxide-semiconductor Radiation-sensitive Field Effect Transistors (RadFET)s into an orbit designed by NASA to probe the heart of the trapped-radiation belts. Nearly 350 days of in situ measurements from the Engineering Radiation Monitor (ERM) (1) demonstrated strong variations of dose rates with time, (2) revealed a critical correlation between the ERM RadFET dosimeters and the ERM Faraday cup data on charged particles, and (3) permitted the mapping of the belts by measuring variation with orbit altitude. This paper provides an update on early results given in a NSREC2012 paper along with details and discussion of the RadFET dosimetry data analyzed . Holmes-Siedle, A.; Goldsten, J.; Maurer, R.; Peplowski, P.; Published by: IEEE Transactions on Nuclear Science Published on: 04/2014 YEAR: 2014 DOI: 10.1109/TNS.2014.2307012 |
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Simulations from our newly expanded ring current-atmosphere interactions model with self-consistent magnetic field (RAM-SCB), now valid out to 9 RE, are compared for the first time with Van Allen Probes observations. The expanded model reproduces the storm time ring current buildup due to the increased convection and inflow of plasma from the magnetotail. It matches Magnetic Electron Ion Spectrometer (MagEIS) observations of the trapped high-energy (>50 keV) ion flux; however, it underestimates the low-energy (<10 keV) Helium, Oxygen, Proton, and Electron (HOPE) observations. The dispersed injections of ring current ions observed with the Energetic particle, Composition, and Thermal plasma (ECT) suite at high (>20 keV) energy are better reproduced using a high-resolution convection model. In agreement with Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) observations, RAM-SCB indicates that the large-scale magnetic field is depressed as close as \~4.5 RE during even a moderate storm. Regions of electromagnetic ion cyclotron instability are predicted on the duskside from \~6 to \~9 RE, indicating that previous studies confined to geosynchronous orbit may have underestimated their scattering effect on the energetic particles. Jordanova, V.; Yu, Y.; Niehof, J.; Skoug, R.; Reeves, G.; Kletzing, C.; Fennell, J.; Spence, H.; Published by: Geophysical Research Letters Published on: 04/2014 YEAR: 2014 DOI: 10.1002/2014GL059533 |
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Van Allen Probes observations of direct wave-particle interactions Quasiperiodic increases, or \textquotedblleftbursts,\textquotedblright of 17\textendash26 keV electron fluxes in conjunction with chorus wave bursts were observed following a plasma injection on 13 January 2013. The pitch angle distributions changed during the burst events, evolving from sinN(α) to distributions that formed maxima at α = 75\textendash80\textdegree, while fluxes at 90\textdegree and <60\textdegree remained nearly unchanged. The observations occurred outside of the plasmasphere in the postmidnight region and were observed by both Van Allen Probes. Density, cyclotron frequency, and pitch angle of the peak flux were used to estimate resonant electron energy. The result of ~15\textendash35 keV is consistent with the energies of the electrons showing the flux enhancements and corresponds to electrons in and above the steep flux gradient that signals the presence of an Alfv\ en boundary in the plasma. The cause of the quasiperiodic nature (on the order of a few minutes) of the bursts is not understood at this time. Fennell, J.; Roeder, J.; Kurth, W.; Henderson, M.; Larsen, B.; Hospodarsky, G.; Wygant, J.; Claudepierre, J.; Blake, J.; Spence, H.; Clemmons, J.; Funsten, H.; Kletzing, C.; Reeves, G.; Published by: Geophysical Research Letters Published on: 03/2014 YEAR: 2014 DOI: 10.1002/2013GL059165 |
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Drastic variations of Earth\textquoterights outer radiation belt electrons ultimately result from various competing source, loss, and transport processes, to which wave-particle interactions are critically important. Using 15 spacecraft including NASA\textquoterights Van Allen Probes, THEMIS, and SAMPEX missions and NOAA\textquoterights GOES and POES constellations, we investigated the evolution of the outer belt during the strong geomagnetic storm of 30 September to 3 October 2012. This storm\textquoterights main phase dropout exhibited enhanced losses to the atmosphere at L* < 4, where the phase space density (PSD) of multi-MeV electrons dropped by over an order of magnitude in <4 h. Based on POES observations of precipitating >1 MeV electrons and energetic protons, SAMPEX >1 MeV electrons, and ground observations of band-limited Pc1-2 wave activity, we show that this sudden loss was consistent with pitch angle scattering by electromagnetic ion cyclotron waves in the dusk magnetic local time sector at 3 < L* < 4. At 4 < L* < 5, local acceleration was also active during the main and early recovery phases, when growing peaks in electron PSD were observed by both Van Allen Probes and THEMIS. This acceleration corresponded to the period when IMF Bz was southward, the AE index was >300 nT, and energetic electron injections and whistler-mode chorus waves were observed throughout the inner magnetosphere for >12 h. After this period, Bz turned northward, and injections, chorus activity, and enhancements in PSD ceased. Overall, the outer belt was depleted by this storm. From the unprecedented level of observations available, we show direct evidence of the competitive nature of different wave-particle interactions controlling relativistic electron fluxes in the outer radiation belt. Turner, D.; Angelopoulos, V.; Li, W.; Bortnik, J.; Ni, B.; Ma, Q.; Thorne, R.; Morley, S.; Henderson, M.; Reeves, G.; Usanova, M.; Mann, I.; Claudepierre, S.; Blake, J.; Baker, D.; Huang, C.-L.; Spence, H.; Kurth, W.; Kletzing, C.; Rodriguez, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 03/2014 YEAR: 2014 DOI: 10.1002/jgra.v119.310.1002/2014JA019770 |
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The dual-spacecraft Van Allen Probes mission has provided a new window into mega electron volt (MeV) particle dynamics in the Earth\textquoterights radiation belts. Observations (up to E ~10 MeV) show clearly the behavior of the outer electron radiation belt at different timescales: months-long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. We present analysis of multi-MeV electron flux and phase space density (PSD) changes during March 2013 in the context of the first year of Van Allen Probes operation. This March period demonstrates the classic signatures both of inward radial diffusive energization and abrupt localized acceleration deep within the outer Van Allen zone (L ~4.0 \textpm 0.5). This reveals graphically that both \textquotedblleftcompeting\textquotedblright mechanisms of multi-MeV electron energization are at play in the radiation belts, often acting almost concurrently or at least in rapid succession. Baker, D.; Jaynes, A.; Li, X.; Henderson, M.; Kanekal, S.; Reeves, G.; Spence, H.; Claudepierre, S.; Fennell, J.; Hudson, M.; Thorne, R.; Foster, J.; Erickson, P.; Malaspina, D.; Wygant, J.; Boyd, A.; Kletzing, C.; Drozdov, A.; Shprits, Y; Published by: Geophysical Research Letters Published on: 03/2014 YEAR: 2014 DOI: 10.1002/2013GL058942 |
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Resonant scattering of energetic electrons by unusual low-frequency hiss We quantify the resonant scattering effects of the unusual low-frequency dawnside plasmaspheric hiss observed on 30 September 2012 by the Van Allen Probes. In contrast to normal (~100\textendash2000 Hz) hiss emissions, this unusual hiss event contained most of its wave power at ~20\textendash200 Hz. Compared to the scattering by normal hiss, the unusual hiss scattering speeds up the loss of ~50\textendash200 keV electrons and produces more pronounced pancake distributions of ~50\textendash100 keV electrons. It is demonstrated that such unusual low-frequency hiss, even with a duration of a couple of hours, plays a particularly important role in the decay and loss process of energetic electrons, resulting in shorter electron lifetimes for ~50\textendash400 keV electrons than normal hiss, and should be carefully incorporated into global modeling of radiation belt electron dynamics during periods of intense injections. Ni, Binbin; Li, Wen; Thorne, Richard; Bortnik, Jacob; Ma, Qianli; Chen, Lunjin; Kletzing, Craig; Kurth, William; Hospodarsky, George; Reeves, Geoffrey; Spence, Harlan; Blake, Bernard; Fennell, Joseph; Claudepierre, Seth; Published by: Geophysical Research Letters Published on: 03/2014 YEAR: 2014 DOI: 10.1002/2014GL059389 |
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Resonant scattering of energetic electrons by unusual low-frequency hiss We quantify the resonant scattering effects of the unusual low-frequency dawnside plasmaspheric hiss observed on 30 September 2012 by the Van Allen Probes. In contrast to normal (~100\textendash2000 Hz) hiss emissions, this unusual hiss event contained most of its wave power at ~20\textendash200 Hz. Compared to the scattering by normal hiss, the unusual hiss scattering speeds up the loss of ~50\textendash200 keV electrons and produces more pronounced pancake distributions of ~50\textendash100 keV electrons. It is demonstrated that such unusual low-frequency hiss, even with a duration of a couple of hours, plays a particularly important role in the decay and loss process of energetic electrons, resulting in shorter electron lifetimes for ~50\textendash400 keV electrons than normal hiss, and should be carefully incorporated into global modeling of radiation belt electron dynamics during periods of intense injections. Ni, Binbin; Li, Wen; Thorne, Richard; Bortnik, Jacob; Ma, Qianli; Chen, Lunjin; Kletzing, Craig; Kurth, William; Hospodarsky, George; Reeves, Geoffrey; Spence, Harlan; Blake, Bernard; Fennell, Joseph; Claudepierre, Seth; Published by: Geophysical Research Letters Published on: 03/2014 YEAR: 2014 DOI: 10.1002/2014GL059389 |
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Combining Time History of Events and Macroscale Interaction during Substorms (THEMIS) wave and particle observations and a quantitative calculation of linear wave growth rate, we demonstrate that magnetosonic (MS) waves can be locally excited by ion ring distributions in the Earth\textquoterights magnetosphere when the ion ring energy is comparable to the local Alfven energy. MS waves in association with ion ring distributions were observed by THEMIS A on 24 November 2010 in the afternoon sector, both outside the plasmapause where the wave spectrum varied with fLHR and inside the plasmapause where the wave frequency band remained nearly constant. Our plasma instability analysis in three different regions shows that higher and narrow frequency band MS waves are excited locally outside the plasmapause, and lower and broad frequency band MS waves are excited in the region where the density slightly increases. However, there is no evidence for wave excitation inside the plasmapause, and wave propagation from a distant source is needed to explain their existence. The simulation of the MS wave growth rate spectra during this event agrees reasonably well with the observed wave magnetic field power spectra. We also simulated a MS wave event on 19 October 2011 in the dusk sector and found that the ion ring distribution with an ion ring energy slightly higher than the local Alfven energy can excite the typical broad band MS waves outside the plasmapause. Ma, Qianli; Li, Wen; Chen, Lunjin; Thorne, Richard; Angelopoulos, Vassilis; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2014 YEAR: 2014 DOI: 10.1002/2013JA019591 magnetosonic waves; ring current; THEMIS observation; wave excitation |
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Quantifying hiss-driven energetic electron precipitation: A detailed conjunction event analysis We analyze a conjunction event between the Van Allen Probes and the low-altitude Polar Orbiting Environmental Satellite (POES) to quantify hiss-driven energetic electron precipitation. A physics-based technique based on quasi-linear diffusion theory is used to estimate the ratio of precipitated and trapped electron fluxes (R), which could be measured by the two-directional POES particle detectors, using wave and plasma parameters observed by the Van Allen Probes. The remarkable agreement between modeling and observations suggests that this technique is applicable for quantifying hiss-driven electron scattering near the bounce loss cone. More importantly, R in the 100\textendash300 keV energy channel measured by multiple POES satellites over a broad L magnetic local time region can potentially provide the spatiotemporal evolution of global hiss wave intensity, which is essential in evaluating radiation belt electron dynamics, but cannot be obtained by in situ equatorial satellites alone. Li, W.; Ni, B.; Thorne, R.; Bortnik, J.; Nishimura, Y.; Green, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Blake, J.; Fennell, J.; Claudepierre, S.; Gu, X.; Published by: Geophysical Research Letters Published on: 02/2014 YEAR: 2014 DOI: 10.1002/2013GL059132 |
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Quantifying hiss-driven energetic electron precipitation: A detailed conjunction event analysis We analyze a conjunction event between the Van Allen Probes and the low-altitude Polar Orbiting Environmental Satellite (POES) to quantify hiss-driven energetic electron precipitation. A physics-based technique based on quasi-linear diffusion theory is used to estimate the ratio of precipitated and trapped electron fluxes (R), which could be measured by the two-directional POES particle detectors, using wave and plasma parameters observed by the Van Allen Probes. The remarkable agreement between modeling and observations suggests that this technique is applicable for quantifying hiss-driven electron scattering near the bounce loss cone. More importantly, R in the 100\textendash300 keV energy channel measured by multiple POES satellites over a broad L magnetic local time region can potentially provide the spatiotemporal evolution of global hiss wave intensity, which is essential in evaluating radiation belt electron dynamics, but cannot be obtained by in situ equatorial satellites alone. Li, W.; Ni, B.; Thorne, R.; Bortnik, J.; Nishimura, Y.; Green, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Blake, J.; Fennell, J.; Claudepierre, S.; Gu, X.; Published by: Geophysical Research Letters Published on: 02/2014 YEAR: 2014 DOI: 10.1002/2013GL059132 |
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Fine structure of large-amplitude chorus wave packets Whistler mode chorus waves in the outer Van Allen belt can have consequences for acceleration of relativistic electrons through wave-particle interactions. New multicomponent waveform measurements have been collected by the Van Allen Probes Electric and Magnetic Field Instrument Suite and Integrated Science\textquoterights Waves instrument. We detect fine structure of chorus elements with peak instantaneous amplitudes of a few hundred picotesla but exceptionally reaching up to 3 nT, i.e., more than 1\% of the background magnetic field. The wave vector direction turns by a few tens of degrees within a single chorus element but also within its subpackets. Our analysis of a significant number of subpackets embedded in rising frequency elements shows that amplitudes of their peaks tend to decrease with frequency. The wave vector is quasi-parallel to the background magnetic field for large-amplitude subpackets, while it turns away from this direction when the amplitudes are weaker. Santolik, O.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Bounds, S.; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058889 |
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Nonstorm time dynamics of electron radiation belts observed by the Van Allen Probes Storm time electron radiation belt dynamics have been widely investigated for many years. Here we present a rarely reported nonstorm time event of electron radiation belt evolution observed by the Van Allen Probes during 21\textendash24 February 2013. Within 2 days, a new belt centering around L=5.8 formed and gradually merged with the original outer belt, with the enhancement of relativistic electron fluxes by a factor of up to 50. Strong chorus waves (with power spectral density up to 10-4nT2/Hz) occurred in the region L>5. Taking into account the local acceleration driven by these chorus waves, the two-dimensional STEERB can approximately reproduce the observed energy spectrums at the center of the new belt. These results clearly illustrate the complexity of electron radiation belt behaviors and the importance of chorus-driven local acceleration even during the nonstorm times. Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; He, Zhaoguo; Zhu, Hui; Zhang, Min; Shen, Chao; Wang, Yuming; Wang, Shui; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; Baker, D.; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058912 |
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Observations of kinetic scale field line resonances We identify electromagnetic field variations from the Van Allen Probes which have the properties of Doppler shifted kinetic scale Alfv\ enic field line resonances. These variations are observed during injections of energetic plasmas into the inner magnetosphere. These waves have scale sizes perpendicular to the magnetic field which are determined to be of the order of an ion gyro-radius (ρi) and less. Cross-spectral analysis of the electric and magnetic fields reveals phase transitions at frequencies correlated with enhancements and depressions in the ratio of the electric and magnetic fields. Modeling shows that these observations are consistent with the excitation of field-line resonances over a broad range of wave numbers perpendicular to the magnetic field (k⊥) extending to k⊥ρi >> 1. The amplitude of these waves is such that E/Bo ≳ Ωi/k⊥ (E, Bo, and Ωi are the wave amplitude, background field strength, and ion gyro-frequency, respectively) leading to ion demagnetization and acceleration for multiple transitions through the wave potential. Chaston, Christopher; Bonnell, J; Wygant, John; Mozer, Forrest; Bale, Stuart; Kersten, Kris; Breneman, Aaron; Kletzing, Craig; Kurth, William; Hospodarsky, George; Smith, Charles; MacDonald, Elizabeth; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058507 |
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Rotationally driven zebra stripes in Earth s inner radiation belt Structured features on top of nominally smooth distributions of radiation-belt particles at Earth have been previously associated with particle acceleration and transport mechanisms powered exclusively by enhanced solar-wind activity1, 2, 3, 4. Although planetary rotation is considered to be important for particle acceleration at Jupiter and Saturn5, 6, 7, 8, 9, the electric field produced in the inner magnetosphere by Earth\textquoterights rotation can change the velocity of trapped particles by only about 1\textendash2 kilometres per second, so rotation has been thought inconsequential for radiation-belt electrons with velocities of about 100,000 kilometres per second. Here we report that the distributions of energetic electrons across the entire spatial extent of Earth\textquoterights inner radiation belt are organized in regular, highly structured and unexpected \textquoteleftzebra stripes\textquoteright, even when the solar-wind activity is low. Modelling reveals that the patterns are produced by Earth\textquoterights rotation. Radiation-belt electrons are trapped in Earth\textquoterights dipole-like magnetic field, where they undergo slow longitudinal drift motion around the planet because of the gradient and curvature of the magnetic field. Earth\textquoterights rotation induces global diurnal variations of magnetic and electric fields that resonantly interact with electrons whose drift period is close to 24 hours, modifying electron fluxes over a broad energy range into regular patterns composed of multiple stripes extending over the entire span of the inner radiation belt. Ukhorskiy, A; Sitnov, M.; Mitchell, D.; Takahashi, K; Lanzerotti, L.; Mauk, B.; Published by: Nature Published on: 01/2014 YEAR: 2014 DOI: 10.1038/nature13046 |
| 2013 |
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The Engineering Radiation Monitor (ERM) measures dose, dose rate and charging currents on the Van Allen Probes mission to study the dynamics of earth\textquoterights Van Allen radiation belts. Early results from this monitor show a variation in dose rates with time, a correlation between the dosimeter and charging current data, a map of charging current versus orbit altitude and a comparison of cumulative dose to pre-launch modeling after 260 days. Solar cell degradation monitor patches track the decrease in solar array output as displacement damage accumulates. Maurer, Richard; Goldsten, John; Peplowski, Patrick; Holmes-Siedle, Andrew; Butler, Michael; Herrmann, Carl; Mauk, Barry; Published by: IEEE Transactions on Nuclear Science Published on: Jan-12-2013 YEAR: 2013 DOI: 10.1109/TNS.2013.2281937 |
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James Van Allen and His Namesake NASA Mission In many ways, James A. Van Allen defined and \textquotedblleftinvented\textquotedblright modern space research. His example showed the way for government-university partners to pursue basic research that also served important national and international goals. He was a tireless advocate for space exploration and for the role of space science in the spectrum of national priorities. Baker, D.; Hoxie, V.; Jaynes, A.; Kale, A.; Kanekal, S.; Li, X.; Reeves, G.; Spence, H.; Published by: Eos, Transactions American Geophysical Union Published on: 12/2013 YEAR: 2013 DOI: 10.1002/eost.v94.4910.1002/2013EO490001 |
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Rapid local acceleration of relativistic radiation-belt electrons by magnetospheric chorus Recent analysis of satellite data obtained during the 9 October 2012 geomagnetic storm identified the development of peaks in electron phase space density1, which are compelling evidence for local electron acceleration in the heart of the outer radiation belt2, 3, but are inconsistent with acceleration by inward radial diffusive transport4, 5. However, the precise physical mechanism responsible for the acceleration on 9 October was not identified. Previous modelling has indicated that a magnetospheric electromagnetic emission known as chorus could be a potential candidate for local electron acceleration6, 7, 8, 9, 10, but a definitive resolution of the importance of chorus for radiation-belt acceleration was not possible because of limitations in the energy range and resolution of previous electron observations and the lack of a dynamic global wave model. Here we report high-resolution electron observations11 obtained during the 9 October storm and demonstrate, using a two-dimensional simulation performed with a recently developed time-varying data-driven model12, that chorus scattering explains the temporal evolution of both the energy and angular distribution of the observed relativistic electron flux increase. Our detailed modelling demonstrates the remarkable efficiency of wave acceleration in the Earth\textquoterights outer radiation belt, and the results presented have potential application to Jupiter, Saturn and other magnetized astrophysical objects. Thorne, R.; Li, W.; Ni, B.; Ma, Q.; Bortnik, J.; Chen, L.; Baker, D.; Spence, H.; Reeves, G.; Henderson, M.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Blake, J.; Fennell, J.; Claudepierre, S.; Kanekal, S.; Published by: Nature Published on: 12/2013 YEAR: 2013 DOI: 10.1038/nature12889 |
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Rapid local acceleration of relativistic radiation-belt electrons by magnetospheric chorus Recent analysis of satellite data obtained during the 9 October 2012 geomagnetic storm identified the development of peaks in electron phase space density1, which are compelling evidence for local electron acceleration in the heart of the outer radiation belt2, 3, but are inconsistent with acceleration by inward radial diffusive transport4, 5. However, the precise physical mechanism responsible for the acceleration on 9 October was not identified. Previous modelling has indicated that a magnetospheric electromagnetic emission known as chorus could be a potential candidate for local electron acceleration6, 7, 8, 9, 10, but a definitive resolution of the importance of chorus for radiation-belt acceleration was not possible because of limitations in the energy range and resolution of previous electron observations and the lack of a dynamic global wave model. Here we report high-resolution electron observations11 obtained during the 9 October storm and demonstrate, using a two-dimensional simulation performed with a recently developed time-varying data-driven model12, that chorus scattering explains the temporal evolution of both the energy and angular distribution of the observed relativistic electron flux increase. Our detailed modelling demonstrates the remarkable efficiency of wave acceleration in the Earth\textquoterights outer radiation belt, and the results presented have potential application to Jupiter, Saturn and other magnetized astrophysical objects. Thorne, R.; Li, W.; Ni, B.; Ma, Q.; Bortnik, J.; Chen, L.; Baker, D.; Spence, H.; Reeves, G.; Henderson, M.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Blake, J.; Fennell, J.; Claudepierre, S.; Kanekal, S.; Published by: Nature Published on: 12/2013 YEAR: 2013 DOI: 10.1038/nature12889 |
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We perform a comprehensive analysis to evaluate hiss-induced scattering effect on the pitch angle evolution and associated decay processes of relativistic electrons. The results show that scattering by the equatorial, highly oblique hiss component is negligible. Quasi-parallel approximation is good for evaluation of hiss-driven electron scattering rates <= 2 MeV. However, realistic wave propagation angles as a function of latitude must be considered to accurately quantify hiss scattering rates above 2 MeV, and ambient plasma density is also a critical parameter. While the first-order cyclotron and the Landau resonances are dominant for hiss scattering < 2 MeV electrons, higher-order resonances become important and even dominant at intermediate pitch angles for ultrarelativistic (>= 3 MeV) electrons. Hiss-induced electron pitch angle evolution shows an initially rapid transport from high to lower pitch angles, with a gradual approach toward equilibrium, and a final exponential decay as a whole. Although hiss scattering rates near the loss cone control the pitch angle evolution and the ultimate loss of ultrarelativistic electrons, the scattering bottleneck significantly affects the loss rate and leads to characteristic top hat-shaped pitch angle distributions at energies < 1 MeV. Decay timescales are on the order of a few days, tens of days, and > 100 days for 500 keV, 2 MeV, and 5 MeV electrons, respectively, consistent with recent observations from the Van Allen Probes and indicating that scattering by hiss can realistically account for the long-term loss process and the pitch angle evolution of relativistic electrons in the plasmasphere following storm time injections. Ni, Binbin; Bortnik, Jacob; Thorne, Richard; Ma, Qianli; Chen, Lunjin; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019260 |
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The Balloon Array for RBSP Relativistic Electron Losses (BARREL) BARREL is a multiple-balloon investigation designed to study electron losses from Earth\textquoterights Radiation Belts. Selected as a NASA Living with a Star Mission of Opportunity, BARREL augments the Radiation Belt Storm Probes mission by providing measurements of relativistic electron precipitation with a pair of Antarctic balloon campaigns that will be conducted during the Austral summers (January-February) of 2013 and 2014. During each campaign, a total of 20 small (\~20 kg) stratospheric balloons will be successively launched to maintain an array of \~5 payloads spread across \~6 hours of magnetic local time in the region that magnetically maps to the radiation belts. Each balloon carries an X-ray spectrometer to measure the bremsstrahlung X-rays produced by precipitating relativistic electrons as they collide with neutrals in the atmosphere, and a DC magnetometer to measure ULF-timescale variations of the magnetic field. BARREL will provide the first balloon measurements of relativistic electron precipitation while comprehensive in situ measurements of both plasma waves and energetic particles are available, and will characterize the spatial scale of precipitation at relativistic energies. All data and analysis software will be made freely available to the scientific community. Millan, R.; McCarthy, M.; Sample, J.; Smith, D.; Thompson, L.; McGaw, D.; Woodger, L.; Hewitt, J.; Comess, M.; Yando, K.; Liang, A.; Anderson, B.; Knezek, N.; Rexroad, W.; Scheiman, J.; Bowers, G.; Halford, A.; Collier, A.; Clilverd, M.; Lin, R.; Hudson, M.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9971-z |
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Although the Earth\textquoterights Van Allen radiation belts were discovered over 50 years ago, the dominant processes responsible for relativistic electron acceleration, transport and loss remain poorly understood. Here we show evidence for the action of coherent acceleration due to resonance with ultra-low frequency waves on a planetary scale. Data from the CRRES probe, and from the recently launched multi-satellite NASA Van Allen Probes mission, with supporting modeling, collectively show coherent ultra-low frequency interactions which high energy resolution data reveals are far more common than either previously thought or observed. The observed modulations and energy-dependent spatial structure indicate a mode of action analogous to a geophysical synchrotron; this new mode of response represents a significant shift in known Van Allen radiation belt dynamics and structure. These periodic collisionless betatron acceleration processes also have applications in understanding the dynamics of, and periodic electromagnetic emissions from, distant plasma-astrophysical systems. Mann, Ian; Lee, E.; Claudepierre, S.; Fennell, J.; Degeling, A.; Rae, I.; Baker, D.; Reeves, G.; Spence, H.; Ozeke, L.; Rankin, R.; Milling, D.; Kale, A.; Friedel, R.; Honary, F.; Published by: Nature Communications Published on: 11/2013 YEAR: 2013 DOI: 10.1038/ncomms3795 |
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Dynamics of Radiation Belt Particles This paper reviews basic concepts of particle dynamics underlying theoretical aspect of radiation belt modeling and data analysis. We outline the theory of adiabatic invariants of quasiperiodic Hamiltonian systems and derive the invariants of particle motion trapped in the radiation belts. We discuss how the nonlinearity of resonant interaction of particles with small-amplitude plasma waves, ubiquitous across the inner magnetosphere, can make particle motion stochastic. Long-term evolution of a stochastic system can be described by the Fokker-Plank (diffusion) equation. We derive the kinetic equation of particle diffusion in the invariant space and discuss its limitations and associated challenges which need to be addressed in forthcoming radiation belt models and data analysis. Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-012-9938-5 |
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The Engineering Radiation Monitor (ERM) measures dose, dose rate and charging currents on the Van Allen Probes mission to study the dynamics of earth\textquoterights Van Allen radiation belts. Early results from this monitor show a variation in dose rates with time, a correlation between the dosimeter and charging current data, a map of charging current versus orbit altitude and a comparison of cumulative dose to pre-launch modeling after 260 days. Solar cell degradation monitor patches track the decrease in solar array output as displacement damage accumulates. Maurer, Richard; Goldsten, J.; Peplowski, P.; Holmes-Siedle, A.; Butler, Michael; Herrmann, C.; Mauk, B.; Published by: Published on: 11/2013 YEAR: 2013 DOI: 10.1109/TNS.2013.2281937 |
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The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on RBSP The Electric and Magnetic Field Instrument and Integrated Science (EMFISIS) investigation on the NASA Radiation Belt Storm Probes (now named the Van Allen Probes) mission provides key wave and very low frequency magnetic field measurements to understand radiation belt acceleration, loss, and transport. The key science objectives and the contribution that EMFISIS makes to providing measurements as well as theory and modeling are described. The key components of the instruments suite, both electronics and sensors, including key functional parameters, calibration, and performance, demonstrate that EMFISIS provides the needed measurements for the science of the RBSP mission. The EMFISIS operational modes and data products, along with online availability and data tools provide the radiation belt science community with one the most complete sets of data ever collected. Kletzing, C.; Kurth, W.; Acuna, M.; MacDowall, R.; Torbert, R.; Averkamp, T.; Bodet, D.; Bounds, S.; Chutter, M.; Connerney, J.; Crawford, D.; Dolan, J.; Dvorsky, R.; Hospodarsky, G.; Howard, J.; Jordanova, V.; Johnson, R.; Kirchner, D.; Mokrzycki, B.; Needell, G.; Odom, J.; Mark, D.; Pfaff, R.; Phillips, J.; Piker, C.; Remington, S.; Rowland, D.; Santolik, O.; Schnurr, R.; Sheppard, D.; Smith, C.; Thorne, R.; Tyler, J.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9993-6 |
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The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on RBSP The Electric and Magnetic Field Instrument and Integrated Science (EMFISIS) investigation on the NASA Radiation Belt Storm Probes (now named the Van Allen Probes) mission provides key wave and very low frequency magnetic field measurements to understand radiation belt acceleration, loss, and transport. The key science objectives and the contribution that EMFISIS makes to providing measurements as well as theory and modeling are described. The key components of the instruments suite, both electronics and sensors, including key functional parameters, calibration, and performance, demonstrate that EMFISIS provides the needed measurements for the science of the RBSP mission. The EMFISIS operational modes and data products, along with online availability and data tools provide the radiation belt science community with one the most complete sets of data ever collected. Kletzing, C.; Kurth, W.; Acuna, M.; MacDowall, R.; Torbert, R.; Averkamp, T.; Bodet, D.; Bounds, S.; Chutter, M.; Connerney, J.; Crawford, D.; Dolan, J.; Dvorsky, R.; Hospodarsky, G.; Howard, J.; Jordanova, V.; Johnson, R.; Kirchner, D.; Mokrzycki, B.; Needell, G.; Odom, J.; Mark, D.; Pfaff, R.; Phillips, J.; Piker, C.; Remington, S.; Rowland, D.; Santolik, O.; Schnurr, R.; Sheppard, D.; Smith, C.; Thorne, R.; Tyler, J.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9993-6 |
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The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on RBSP The Electric and Magnetic Field Instrument and Integrated Science (EMFISIS) investigation on the NASA Radiation Belt Storm Probes (now named the Van Allen Probes) mission provides key wave and very low frequency magnetic field measurements to understand radiation belt acceleration, loss, and transport. The key science objectives and the contribution that EMFISIS makes to providing measurements as well as theory and modeling are described. The key components of the instruments suite, both electronics and sensors, including key functional parameters, calibration, and performance, demonstrate that EMFISIS provides the needed measurements for the science of the RBSP mission. The EMFISIS operational modes and data products, along with online availability and data tools provide the radiation belt science community with one the most complete sets of data ever collected. Kletzing, C.; Kurth, W.; Acuna, M.; MacDowall, R.; Torbert, R.; Averkamp, T.; Bodet, D.; Bounds, S.; Chutter, M.; Connerney, J.; Crawford, D.; Dolan, J.; Dvorsky, R.; Hospodarsky, G.; Howard, J.; Jordanova, V.; Johnson, R.; Kirchner, D.; Mokrzycki, B.; Needell, G.; Odom, J.; Mark, D.; Pfaff, R.; Phillips, J.; Piker, C.; Remington, S.; Rowland, D.; Santolik, O.; Schnurr, R.; Sheppard, D.; Smith, C.; Thorne, R.; Tyler, J.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9993-6 |
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The Electric Field and Waves (EFW) Instruments on the Radiation Belt Storm Probes Mission The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by \~15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the \textquotedbllefthighest quality\textquotedblright events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing et al. Space Sci. Rev. 2013). Wygant, J.; Bonnell, J; Goetz, K.; Ergun, R.E.; Mozer, F.; Bale, S.D.; Ludlam, M.; Turin, P.; Harvey, P.R.; Hochmann, R.; Harps, K.; Dalton, G.; McCauley, J.; Rachelson, W.; Gordon, D.; Donakowski, B.; Shultz, C.; Smith, C.; Diaz-Aguado, M.; Fischer, J.; Heavner, S.; Berg, P.; Malaspina, D.; Bolton, M.; Hudson, M.; Strangeway, R.; Baker, D.; Li, X.; Albert, J.; Foster, J.C.; Chaston, C.C.; Mann, I.; Donovan, E.; Cully, C.M.; Cattell, C.; Krasnoselskikh, V.; Kersten, K.; Brenneman, A; Tao, J.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-0013-7 |
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The Engineering Radiation Monitor for the Radiation Belt Storm Probes Mission An Engineering Radiation Monitor (ERM) has been developed as a supplementary spacecraft subsystem for NASA\textquoterights Radiation Belt Storm Probes (RBSP) mission. The ERM will monitor total dose and deep dielectric charging at each RBSP spacecraft in real time. Configured to take the place of spacecraft balance mass, the ERM contains an array of eight dosimeters and two buried conductive plates. The dosimeters are mounted under covers of varying shielding thickness to obtain a dose-depth curve and characterize the electron and proton contributions to total dose. A 3-min readout cadence coupled with an initial sensitivity of \~0.01 krad should enable dynamic measurements of dose rate throughout the 9-hr RBSP orbit. The dosimeters are Radiation-sensing Field Effect Transistors (RadFETs) and operate at zero bias to preserve their response even when powered off. The range of the RadFETs extends above 1000 krad to avoid saturation over the expected duration of the mission. Two large-area (\~10 cm2) charge monitor plates set behind different thickness covers will measure the dynamic currents of weakly-penetrating electrons that can be potentially hazardous to sensitive electronic components within the spacecraft. The charge monitors can handle large events without saturating (\~3000 fA/cm2) and provide sufficient sensitivity (\~0.1 fA/cm2) to gauge quiescent conditions. High time-resolution (5 s) monitoring allows detection of rapid changes in flux and enables correlation of spacecraft anomalies with local space weather conditions. Although primarily intended as an engineering subsystem to monitor spacecraft radiation levels, real-time data from the ERM may also prove useful or interesting to a larger community. Goldsten, J.; Maurer, R.; Peplowski, P.; Holmes-Siedle, A.; Herrmann, C.; Mauk, B.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-012-9917-x |
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Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) The Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on the two Van Allen Probes spacecraft is the magnetosphere ring current instrument that will provide data for answering the three over-arching questions for the Van Allen Probes Program: RBSPICE will determine \textquotedbllefthow space weather creates the storm-time ring current around Earth, how that ring current supplies and supports the creation of the radiation belt populations,\textquotedblright and how the ring current is involved in radiation belt losses. RBSPICE is a time-of-flight versus total energy instrument that measures ions over the energy range from \~20 keV to \~1 MeV. RBSPICE will also measure electrons over the energy range \~25 keV to \~1 MeV in order to provide instrument background information in the radiation belts. A description of the instrument and its data products are provided in this chapter. Mitchell, D.; Lanzerotti, L.; Kim, C.; Stokes, M.; Ho, G.; Cooper, S.; UKHORSKIY, A; Manweiler, J.; Jaskulek, S.; Haggerty, D.; Brandt, P.; SITNOV, M; Keika, K.; Hayes, J.; Brown, L.; Gurnee, R.; Hutcheson, J.; Nelson, K.; Paschalidis, N.; Rossano, E.; Kerem, S.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9965-x |
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Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) The Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on the two Van Allen Probes spacecraft is the magnetosphere ring current instrument that will provide data for answering the three over-arching questions for the Van Allen Probes Program: RBSPICE will determine \textquotedbllefthow space weather creates the storm-time ring current around Earth, how that ring current supplies and supports the creation of the radiation belt populations,\textquotedblright and how the ring current is involved in radiation belt losses. RBSPICE is a time-of-flight versus total energy instrument that measures ions over the energy range from \~20 keV to \~1 MeV. RBSPICE will also measure electrons over the energy range \~25 keV to \~1 MeV in order to provide instrument background information in the radiation belts. A description of the instrument and its data products are provided in this chapter. Mitchell, D.; Lanzerotti, L.; Kim, C.; Stokes, M.; Ho, G.; Cooper, S.; UKHORSKIY, A; Manweiler, J.; Jaskulek, S.; Haggerty, D.; Brandt, P.; SITNOV, M; Keika, K.; Hayes, J.; Brown, L.; Gurnee, R.; Hutcheson, J.; Nelson, K.; Paschalidis, N.; Rossano, E.; Kerem, S.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9965-x |
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Radiation Belt Storm Probes\textemdashObservatory and Environments The National Aeronautics and Space Administration\textquoterights (NASA\textquoterights) Radiation Belt Storm Probe (RBSP) is an Earth-orbiting mission that launched August 30, 2012, and is the latest science mission in NASA\textquoterights Living with a Star Program. The RBSP mission will investigate, characterize and understand the physical dynamics of the radiation belts, as well as the influence of the Sun on the Earth\textquoterights environment, by measuring particles, electric and magnetic fields and waves that comprise geospace. The mission is composed of two identically instrumented spinning observatories in an elliptical orbit around earth with 600 km perigee, 30,000 km apogee and 10o inclination to provide full sampling of the Van Allen radiation belts. The twin RBSP observatories (recently renamed the Van Allen Probes) will follow slightly different orbits and will lap each other four times per year, offering simultaneous measurements over a range of observatory separation distances. A description of the observatory environment is provided along with protection for sensitive electronics to support operations in the harsh radiation belt environment. Spacecraft and subsystem key characteristics and instrument accommodations are included that allow the RBSP science objectives to be met. Kirby, Karen; Artis, David; Bushman, Stewart; Butler, Michael; Conde, Rich; Cooper, Stan; Fretz, Kristen; Herrmann, Carl; Hill, Adrian; Kelley, Jeff; Maurer, Richard; Nichols, Richard; Ottman, Geffrey; Reid, Mark; Rogers, Gabe; Srinivasan, Dipak; Troll, John; Williams, Bruce; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-012-9949-2 |
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Particle acceleration and loss in the million electron Volt (MeV) energy range (and above) is the least understood aspect of radiation belt science. In order to measure cleanly and separately both the energetic electron and energetic proton components, there is a need for a carefully designed detector system. The Relativistic Electron-Proton Telescope (REPT) on board the Radiation Belt Storm Probe (RBSP) pair of spacecraft consists of a stack of high-performance silicon solid-state detectors in a telescope configuration, a collimation aperture, and a thick case surrounding the detector stack to shield the sensors from penetrating radiation and bremsstrahlung. The instrument points perpendicular to the spin axis of the spacecraft and measures high-energy electrons (up to \~20 MeV) with excellent sensitivity and also measures magnetospheric and solar protons to energies well above E=100 MeV. The instrument has a large geometric factor (g=0.2 cm2 sr) to get reasonable count rates (above background) at the higher energies and yet will not saturate at the lower energy ranges. There must be fast enough electronics to avert undue dead-time limitations and chance coincidence effects. The key goal for the REPT design is to measure the directional electron intensities (in the range 10-2\textendash106 particles/cm2 s sr MeV) and energy spectra (ΔE/E\~25 \%) throughout the slot and outer radiation belt region. Present simulations and detailed laboratory calibrations show that an excellent design has been attained for the RBSP needs. We describe the engineering design, operational approaches, science objectives, and planned data products for REPT. Baker, D.; Kanekal, S.; Hoxie, V.; Batiste, S.; Bolton, M.; Li, X.; Elkington, S.; Monk, S.; Reukauf, R.; Steg, S.; Westfall, J.; Belting, C.; Bolton, B.; Braun, D.; Cervelli, B.; Hubbell, K.; Kien, M.; Knappmiller, S.; Wade, S.; Lamprecht, B.; Stevens, K.; Wallace, J.; Yehle, A.; Spence, H.; Friedel, R.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-012-9950-9 |
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The Radiation Belt Storm Probes (RBSP)-Energetic Particle, Composition, and Thermal Plasma (ECT) suite contains an innovative complement of particle instruments to ensure the highest quality measurements ever made in the inner magnetosphere and radiation belts. The coordinated RBSP-ECT particle measurements, analyzed in combination with fields and waves observations and state-of-the-art theory and modeling, are necessary for understanding the acceleration, global distribution, and variability of radiation belt electrons and ions, key science objectives of NASA\textquoterights Living With a Star program and the Van Allen Probes mission. The RBSP-ECT suite consists of three highly-coordinated instruments: the Magnetic Electron Ion Spectrometer (MagEIS), the Helium Oxygen Proton Electron (HOPE) sensor, and the Relativistic Electron Proton Telescope (REPT). Collectively they cover, continuously, the full electron and ion spectra from one eV to 10\textquoterights of MeV with sufficient energy resolution, pitch angle coverage and resolution, and with composition measurements in the critical energy range up to 50 keV and also from a few to 50 MeV/nucleon. All three instruments are based on measurement techniques proven in the radiation belts. The instruments use those proven techniques along with innovative new designs, optimized for operation in the most extreme conditions in order to provide unambiguous separation of ions and electrons and clean energy responses even in the presence of extreme penetrating background environments. The design, fabrication and operation of ECT spaceflight instrumentation in the harsh radiation belt environment ensure that particle measurements have the fidelity needed for closure in answering key mission science questions. ECT instrument details are provided in companion papers in this same issue. In this paper, we describe the science objectives of the RBSP-ECT instrument suite on the Van Allen Probe spacecraft within the context of the overall mission objectives, indicate how the characteristics of the instruments satisfy the requirements to achieve these objectives, provide information about science data collection and dissemination, and conclude with a description of some early mission results. Spence, H.; Reeves, G.; Baker, D.; Blake, J.; Bolton, M.; Bourdarie, S.; Chan, A.; Claudpierre, S.; Clemmons, J.; Cravens, J.; Elkington, S.; Fennell, J.; Friedel, R.; Funsten, H.; Goldstein, J.; Green, J.; Guthrie, A.; Henderson, M.; Horne, R.; Hudson, M.; Jahn, J.-M.; Jordanova, V.; Kanekal, S.; Klatt, B.; Larsen, B.; Li, X.; MacDonald, E.; Mann, I.R.; Niehof, J.; O\textquoterightBrien, T.; Onsager, T.; Salvaggio, D.; Skoug, R.; Smith, S.; Suther, L.; Thomsen, M.; Thorne, R.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: DOI: 10.1007/s11214-013-0007-5 |
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The Radiation Belt Storm Probes (RBSP)-Energetic Particle, Composition, and Thermal Plasma (ECT) suite contains an innovative complement of particle instruments to ensure the highest quality measurements ever made in the inner magnetosphere and radiation belts. The coordinated RBSP-ECT particle measurements, analyzed in combination with fields and waves observations and state-of-the-art theory and modeling, are necessary for understanding the acceleration, global distribution, and variability of radiation belt electrons and ions, key science objectives of NASA\textquoterights Living With a Star program and the Van Allen Probes mission. The RBSP-ECT suite consists of three highly-coordinated instruments: the Magnetic Electron Ion Spectrometer (MagEIS), the Helium Oxygen Proton Electron (HOPE) sensor, and the Relativistic Electron Proton Telescope (REPT). Collectively they cover, continuously, the full electron and ion spectra from one eV to 10\textquoterights of MeV with sufficient energy resolution, pitch angle coverage and resolution, and with composition measurements in the critical energy range up to 50 keV and also from a few to 50 MeV/nucleon. All three instruments are based on measurement techniques proven in the radiation belts. The instruments use those proven techniques along with innovative new designs, optimized for operation in the most extreme conditions in order to provide unambiguous separation of ions and electrons and clean energy responses even in the presence of extreme penetrating background environments. The design, fabrication and operation of ECT spaceflight instrumentation in the harsh radiation belt environment ensure that particle measurements have the fidelity needed for closure in answering key mission science questions. ECT instrument details are provided in companion papers in this same issue. In this paper, we describe the science objectives of the RBSP-ECT instrument suite on the Van Allen Probe spacecraft within the context of the overall mission objectives, indicate how the characteristics of the instruments satisfy the requirements to achieve these objectives, provide information about science data collection and dissemination, and conclude with a description of some early mission results. Spence, H.; Reeves, G.; Baker, D.; Blake, J.; Bolton, M.; Bourdarie, S.; Chan, A.; Claudpierre, S.; Clemmons, J.; Cravens, J.; Elkington, S.; Fennell, J.; Friedel, R.; Funsten, H.; Goldstein, J.; Green, J.; Guthrie, A.; Henderson, M.; Horne, R.; Hudson, M.; Jahn, J.-M.; Jordanova, V.; Kanekal, S.; Klatt, B.; Larsen, B.; Li, X.; MacDonald, E.; Mann, I.R.; Niehof, J.; O\textquoterightBrien, T.; Onsager, T.; Salvaggio, D.; Skoug, R.; Smith, S.; Suther, L.; Thomsen, M.; Thorne, R.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: DOI: 10.1007/s11214-013-0007-5 |
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The Radiation Belt Storm Probes (RBSP)-Energetic Particle, Composition, and Thermal Plasma (ECT) suite contains an innovative complement of particle instruments to ensure the highest quality measurements ever made in the inner magnetosphere and radiation belts. The coordinated RBSP-ECT particle measurements, analyzed in combination with fields and waves observations and state-of-the-art theory and modeling, are necessary for understanding the acceleration, global distribution, and variability of radiation belt electrons and ions, key science objectives of NASA\textquoterights Living With a Star program and the Van Allen Probes mission. The RBSP-ECT suite consists of three highly-coordinated instruments: the Magnetic Electron Ion Spectrometer (MagEIS), the Helium Oxygen Proton Electron (HOPE) sensor, and the Relativistic Electron Proton Telescope (REPT). Collectively they cover, continuously, the full electron and ion spectra from one eV to 10\textquoterights of MeV with sufficient energy resolution, pitch angle coverage and resolution, and with composition measurements in the critical energy range up to 50 keV and also from a few to 50 MeV/nucleon. All three instruments are based on measurement techniques proven in the radiation belts. The instruments use those proven techniques along with innovative new designs, optimized for operation in the most extreme conditions in order to provide unambiguous separation of ions and electrons and clean energy responses even in the presence of extreme penetrating background environments. The design, fabrication and operation of ECT spaceflight instrumentation in the harsh radiation belt environment ensure that particle measurements have the fidelity needed for closure in answering key mission science questions. ECT instrument details are provided in companion papers in this same issue. In this paper, we describe the science objectives of the RBSP-ECT instrument suite on the Van Allen Probe spacecraft within the context of the overall mission objectives, indicate how the characteristics of the instruments satisfy the requirements to achieve these objectives, provide information about science data collection and dissemination, and conclude with a description of some early mission results. Spence, H.; Reeves, G.; Baker, D.; Blake, J.; Bolton, M.; Bourdarie, S.; Chan, A.; Claudpierre, S.; Clemmons, J.; Cravens, J.; Elkington, S.; Fennell, J.; Friedel, R.; Funsten, H.; Goldstein, J.; Green, J.; Guthrie, A.; Henderson, M.; Horne, R.; Hudson, M.; Jahn, J.-M.; Jordanova, V.; Kanekal, S.; Klatt, B.; Larsen, B.; Li, X.; MacDonald, E.; Mann, I.R.; Niehof, J.; O\textquoterightBrien, T.; Onsager, T.; Salvaggio, D.; Skoug, R.; Smith, S.; Suther, L.; Thomsen, M.; Thorne, R.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: DOI: 10.1007/s11214-013-0007-5 |
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The Radiation Belt Storm Probes (RBSP)-Energetic Particle, Composition, and Thermal Plasma (ECT) suite contains an innovative complement of particle instruments to ensure the highest quality measurements ever made in the inner magnetosphere and radiation belts. The coordinated RBSP-ECT particle measurements, analyzed in combination with fields and waves observations and state-of-the-art theory and modeling, are necessary for understanding the acceleration, global distribution, and variability of radiation belt electrons and ions, key science objectives of NASA\textquoterights Living With a Star program and the Van Allen Probes mission. The RBSP-ECT suite consists of three highly-coordinated instruments: the Magnetic Electron Ion Spectrometer (MagEIS), the Helium Oxygen Proton Electron (HOPE) sensor, and the Relativistic Electron Proton Telescope (REPT). Collectively they cover, continuously, the full electron and ion spectra from one eV to 10\textquoterights of MeV with sufficient energy resolution, pitch angle coverage and resolution, and with composition measurements in the critical energy range up to 50 keV and also from a few to 50 MeV/nucleon. All three instruments are based on measurement techniques proven in the radiation belts. The instruments use those proven techniques along with innovative new designs, optimized for operation in the most extreme conditions in order to provide unambiguous separation of ions and electrons and clean energy responses even in the presence of extreme penetrating background environments. The design, fabrication and operation of ECT spaceflight instrumentation in the harsh radiation belt environment ensure that particle measurements have the fidelity needed for closure in answering key mission science questions. ECT instrument details are provided in companion papers in this same issue. In this paper, we describe the science objectives of the RBSP-ECT instrument suite on the Van Allen Probe spacecraft within the context of the overall mission objectives, indicate how the characteristics of the instruments satisfy the requirements to achieve these objectives, provide information about science data collection and dissemination, and conclude with a description of some early mission results. Spence, H.; Reeves, G.; Baker, D.; Blake, J.; Bolton, M.; Bourdarie, S.; Chan, A.; Claudpierre, S.; Clemmons, J.; Cravens, J.; Elkington, S.; Fennell, J.; Friedel, R.; Funsten, H.; Goldstein, J.; Green, J.; Guthrie, A.; Henderson, M.; Horne, R.; Hudson, M.; Jahn, J.-M.; Jordanova, V.; Kanekal, S.; Klatt, B.; Larsen, B.; Li, X.; MacDonald, E.; Mann, I.R.; Niehof, J.; O\textquoterightBrien, T.; Onsager, T.; Salvaggio, D.; Skoug, R.; Smith, S.; Suther, L.; Thomsen, M.; Thorne, R.; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: DOI: 10.1007/s11214-013-0007-5 |
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Science Objectives and Rationale for the Radiation Belt Storm Probes Mission The NASA Radiation Belt Storm Probes (RBSP) mission addresses how populations of high energy charged particles are created, vary, and evolve in space environments, and specifically within Earth\textquoterights magnetically trapped radiation belts. RBSP, with a nominal launch date of August 2012, comprises two spacecraft making in situ measurements for at least 2 years in nearly the same highly elliptical, low inclination orbits (1.1\texttimes5.8 RE, 10o). The orbits are slightly different so that 1 spacecraft laps the other spacecraft about every 2.5 months, allowing separation of spatial from temporal effects over spatial scales ranging from \~0.1 to 5 RE. The uniquely comprehensive suite of instruments, identical on the two spacecraft, measures all of the particle (electrons, ions, ion composition), fields (E and B), and wave distributions (d E and d B) that are needed to resolve the most critical science questions. Here we summarize the high level science objectives for the RBSP mission, provide historical background on studies of Earth and planetary radiation belts, present examples of the most compelling scientific mysteries of the radiation belts, present the mission design of the RBSP mission that targets these mysteries and objectives, present the observation and measurement requirements for the mission, and introduce the instrumentation that will deliver these measurements. This paper references and is followed by a number of companion papers that describe the details of the RBSP mission, spacecraft, and instruments. Mauk, B.; Fox, N.; Kanekal, S.; Kessel, R.; Sibeck, D.; UKHORSKIY, A; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-012-9908-y |
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In this study we present 3-D data assimilation using CRRES data and 3-D Versatile Electron Radiation Belt Model (VERB) using a newly developed operator-splitting method. Simulations with synthetic data show that the operator-splitting Kalman filtering technique proposed in this study can successfully reconstruct the underlying dynamic evolution of the radiation belts. The method is further verified by the comparison with the conventional Kalman filter. We applied the new approach to 3-D data assimilation of real data to globally reconstruct the dynamics of the radiation belts using pitch angle, energy, and L shell dependent CRRES observations. An L shell time cross section of the global data assimilation results for nearly equatorially mirroring particles and high and low values of the first adiabatic invariants clearly show the difference between the radial profiles of phase space density. At μ = 700 MeV/G cross section of the global reanalysis shows a clear peak in the phase space density, while at lower energy of 70 MeV/G the profiles are monotonic. Since the radial profiles are obtained from one global reanalysis, the differences in the profiles reflect the differences in the underlying physical processes responsible for the dynamic evolution of the radiation belt energetic and relativistic electrons. Shprits, Yuri; Kellerman, Adam; Kondrashov, Dmitri; Subbotin, Dmitriy; Published by: Geophysical Research Letters Published on: 10/2013 YEAR: 2013 DOI: 10.1002/grl.50969 |
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We adopt a physics-based technique to infer chorus wave amplitudes from the low-altitude electron population (30\textendash100 keV) measured by multiple Polar Orbiting Environmental Satellites (POES), which provide extensive coverage over a broad region in L-shell and magnetic local time (MLT). This technique is validated by analyzing conjunction events between the Van Allen Probes measuring chorus wave amplitudes near the equator and POES satellites measuring the 30\textendash100 keV electron population at the conjugate low altitudes. We apply this technique to construct the chorus wave distributions during the 8\textendash9 October storm in 2012 and demonstrate that the inferred chorus wave amplitudes agree reasonably well with conjugate measurements of chorus wave amplitudes from the Van Allen Probes. The evolution of the chorus wave intensity inferred from low-altitude electron measurements can provide real-time global estimates of the chorus wave intensity, which cannot be obtained from in situ chorus wave measurements by equatorial satellites alone, but is crucial in quantifying radiation belt electron dynamics. Li, W.; Ni, B.; Thorne, R.; Bortnik, J.; Green, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Published by: Geophysical Research Letters Published on: 09/2013 YEAR: 2013 DOI: 10.1002/grl.v40.1710.1002/grl.50920 |
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We adopt a physics-based technique to infer chorus wave amplitudes from the low-altitude electron population (30\textendash100 keV) measured by multiple Polar Orbiting Environmental Satellites (POES), which provide extensive coverage over a broad region in L-shell and magnetic local time (MLT). This technique is validated by analyzing conjunction events between the Van Allen Probes measuring chorus wave amplitudes near the equator and POES satellites measuring the 30\textendash100 keV electron population at the conjugate low altitudes. We apply this technique to construct the chorus wave distributions during the 8\textendash9 October storm in 2012 and demonstrate that the inferred chorus wave amplitudes agree reasonably well with conjugate measurements of chorus wave amplitudes from the Van Allen Probes. The evolution of the chorus wave intensity inferred from low-altitude electron measurements can provide real-time global estimates of the chorus wave intensity, which cannot be obtained from in situ chorus wave measurements by equatorial satellites alone, but is crucial in quantifying radiation belt electron dynamics. Li, W.; Ni, B.; Thorne, R.; Bortnik, J.; Green, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Published by: Geophysical Research Letters Published on: 09/2013 YEAR: 2013 DOI: 10.1002/grl.v40.1710.1002/grl.50920 |
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The HOPE mass spectrometer of the Radiation Belt Storm Probes (RBSP) mission (renamed the Van Allen Probes) is designed to measure the in situ plasma ion and electron fluxes over 4π sr at each RBSP spacecraft within the terrestrial radiation belts. The scientific goal is to understand the underlying physical processes that govern the radiation belt structure and dynamics. Spectral measurements for both ions and electrons are acquired over 1 eV to 50 keV in 36 log-spaced steps at an energy resolution ΔE FWHM/E≈15 \%. The dominant ion species (H+, He+, and O+) of the magnetosphere are identified using foil-based time-of-flight (TOF) mass spectrometry with channel electron multiplier (CEM) detectors. Angular measurements are derived using five polar pixels coplanar with the spacecraft spin axis, and up to 16 azimuthal bins are acquired for each polar pixel over time as the spacecraft spins. Ion and electron measurements are acquired on alternate spacecraft spins. HOPE incorporates several new methods to minimize and monitor the background induced by penetrating particles in the harsh environment of the radiation belts. The absolute efficiencies of detection are continuously monitored, enabling precise, quantitative measurements of electron and ion fluxes and ion species abundances throughout the mission. We describe the engineering approaches for plasma measurements in the radiation belts and present summaries of HOPE measurement strategy and performance. Funsten, H.; Skoug, R.; Guthrie, A.; MacDonald, E.; Baldonado, J.; Harper, R.; Henderson, K.; Kihara, K.; Lake, J.; Larsen, B.; Puckett, A.; Vigil, V.; Friedel, R.; Henderson, M.; Niehof, J.; Reeves, G.; Thomsen, M.; Hanley, J.; George, D.; Jahn, J.-M.; Cortinas, S.; Santos, Los; Dunn, G.; Edlund, E.; Ferris, M.; Freeman, M.; Maple, M.; Nunez, C.; Taylor, T.; Toczynski, W.; Urdiales, C.; Spence, H.; Cravens, J.; Suther, L.; Chen, J.; Published by: Space Science Reviews Published on: 08/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9968-7 |
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The HOPE mass spectrometer of the Radiation Belt Storm Probes (RBSP) mission (renamed the Van Allen Probes) is designed to measure the in situ plasma ion and electron fluxes over 4π sr at each RBSP spacecraft within the terrestrial radiation belts. The scientific goal is to understand the underlying physical processes that govern the radiation belt structure and dynamics. Spectral measurements for both ions and electrons are acquired over 1 eV to 50 keV in 36 log-spaced steps at an energy resolution ΔE FWHM/E≈15 \%. The dominant ion species (H+, He+, and O+) of the magnetosphere are identified using foil-based time-of-flight (TOF) mass spectrometry with channel electron multiplier (CEM) detectors. Angular measurements are derived using five polar pixels coplanar with the spacecraft spin axis, and up to 16 azimuthal bins are acquired for each polar pixel over time as the spacecraft spins. Ion and electron measurements are acquired on alternate spacecraft spins. HOPE incorporates several new methods to minimize and monitor the background induced by penetrating particles in the harsh environment of the radiation belts. The absolute efficiencies of detection are continuously monitored, enabling precise, quantitative measurements of electron and ion fluxes and ion species abundances throughout the mission. We describe the engineering approaches for plasma measurements in the radiation belts and present summaries of HOPE measurement strategy and performance. Funsten, H.; Skoug, R.; Guthrie, A.; MacDonald, E.; Baldonado, J.; Harper, R.; Henderson, K.; Kihara, K.; Lake, J.; Larsen, B.; Puckett, A.; Vigil, V.; Friedel, R.; Henderson, M.; Niehof, J.; Reeves, G.; Thomsen, M.; Hanley, J.; George, D.; Jahn, J.-M.; Cortinas, S.; Santos, Los; Dunn, G.; Edlund, E.; Ferris, M.; Freeman, M.; Maple, M.; Nunez, C.; Taylor, T.; Toczynski, W.; Urdiales, C.; Spence, H.; Cravens, J.; Suther, L.; Chen, J.; Published by: Space Science Reviews Published on: 08/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9968-7 |
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Both plasmaspheric hiss and chorus waves were observed simultaneously by the two Van Allen Probes in association with substorm-injected energetic electrons. Probe A, located inside the plasmasphere in the postdawn sector, observed intense plasmaspheric hiss, whereas Probe B observed chorus waves outside the plasmasphere just before dawn. Dispersed injections of energetic electrons were observed in the dayside outer plasmasphere associated with significant intensification of plasmaspheric hiss at frequencies down to ~20 Hz, much lower than typical hiss wave frequencies of 100\textendash2000 Hz. In the outer plasmasphere, the upper energy of injected electrons agrees well with the minimum cyclotron resonant energy calculated for the lower cutoff frequency of the observed hiss, and computed convective linear growth rates indicate instability at the observed low frequencies. This suggests that the unusual low-frequency plasmaspheric hiss is likely to be amplified in the outer plasmasphere due to the injected energetic electrons. Li, W.; Thorne, R.; Bortnik, J.; Reeves, G.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Blake, J.; Fennell, J.; Claudepierre, S.; Wygant, J.; Thaller, S.; Published by: Geophysical Research Letters Published on: 08/2013 YEAR: 2013 DOI: 10.1002/grl.50787 |
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Both plasmaspheric hiss and chorus waves were observed simultaneously by the two Van Allen Probes in association with substorm-injected energetic electrons. Probe A, located inside the plasmasphere in the postdawn sector, observed intense plasmaspheric hiss, whereas Probe B observed chorus waves outside the plasmasphere just before dawn. Dispersed injections of energetic electrons were observed in the dayside outer plasmasphere associated with significant intensification of plasmaspheric hiss at frequencies down to ~20 Hz, much lower than typical hiss wave frequencies of 100\textendash2000 Hz. In the outer plasmasphere, the upper energy of injected electrons agrees well with the minimum cyclotron resonant energy calculated for the lower cutoff frequency of the observed hiss, and computed convective linear growth rates indicate instability at the observed low frequencies. This suggests that the unusual low-frequency plasmaspheric hiss is likely to be amplified in the outer plasmasphere due to the injected energetic electrons. Li, W.; Thorne, R.; Bortnik, J.; Reeves, G.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Blake, J.; Fennell, J.; Claudepierre, S.; Wygant, J.; Thaller, S.; Published by: Geophysical Research Letters Published on: 08/2013 YEAR: 2013 DOI: 10.1002/grl.50787 |
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Electron Acceleration in the Heart of the Van Allen Radiation Belts The Van Allen radiation belts contain ultrarelativistic electrons trapped in Earth\textquoterights magnetic field. Since their discovery in 1958, a fundamental unanswered question has been how electrons can be accelerated to such high energies. Two classes of processes have been proposed: transport and acceleration of electrons from a source population located outside the radiation belts (radial acceleration) or acceleration of lower-energy electrons to relativistic energies in situ in the heart of the radiation belts (local acceleration). We report measurements from NASA\textquoterights Van Allen Radiation Belt Storm Probes that clearly distinguish between the two types of acceleration. The observed radial profiles of phase space density are characteristic of local acceleration in the heart of the radiation belts and are inconsistent with a predominantly radial acceleration process. Reeves, G.; Spence, H.; Henderson, M.; Morley, S.; Friedel, R.; Funsten, H.; Baker, D.; Kanekal, S.; Blake, J.; Fennell, J.; Claudepierre, S.; Thorne, R.; Turner, D.; Kletzing, C.; Kurth, W.; Larsen, B.; Niehof, J.; Published by: Science Published on: 07/2013 YEAR: 2013 DOI: 10.1126/science.1237743 |
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Electron Acceleration in the Heart of the Van Allen Radiation Belts The Van Allen radiation belts contain ultrarelativistic electrons trapped in Earth\textquoterights magnetic field. Since their discovery in 1958, a fundamental unanswered question has been how electrons can be accelerated to such high energies. Two classes of processes have been proposed: transport and acceleration of electrons from a source population located outside the radiation belts (radial acceleration) or acceleration of lower-energy electrons to relativistic energies in situ in the heart of the radiation belts (local acceleration). We report measurements from NASA\textquoterights Van Allen Radiation Belt Storm Probes that clearly distinguish between the two types of acceleration. The observed radial profiles of phase space density are characteristic of local acceleration in the heart of the radiation belts and are inconsistent with a predominantly radial acceleration process. Reeves, G.; Spence, H.; Henderson, M.; Morley, S.; Friedel, R.; Funsten, H.; Baker, D.; Kanekal, S.; Blake, J.; Fennell, J.; Claudepierre, S.; Thorne, R.; Turner, D.; Kletzing, C.; Kurth, W.; Larsen, B.; Niehof, J.; Published by: Science Published on: 07/2013 YEAR: 2013 DOI: 10.1126/science.1237743 |
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A quantitative analysis is performed on the decay of an unusual ring of relativistic electrons between 3 and 3.5 RE, which was observed by the Relativistic Electron Proton Telescope instrument on the Van Allen probes. The ring formed on 3 September 2012 during the main phase of a magnetic storm due to the partial depletion of the outer radiation belt for L > 3.5, and this remnant belt of relativistic electrons persisted at energies above 2 MeV, exhibiting only slow decay, until it was finally destroyed during another magnetic storm on 1 October. This long-term stability of the relativistic electron ring was associated with the rapid outward migration and maintenance of the plasmapause to distances greater than L = 4. The remnant ring was thus immune from the dynamic process, which caused rapid rebuilding of the outer radiation belt at L > 4, and was only subject to slow decay due to pitch angle scattering by plasmaspheric hiss on timescales exceeding 10\textendash20 days for electron energies above 3 MeV. At lower energies, the decay is much more rapid, consistent with the absence of a long-duration electron ring at energies below 2 MeV. Thorne, R.; Li, W.; Ni, B.; Ma, Q.; Bortnik, J.; Baker, D.; Spence, H.; Reeves, G.; Henderson, M.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Turner, D.; Angelopoulos, V.; Published by: Geophysical Research Letters Published on: 06/2013 YEAR: 2013 DOI: 10.1002/grl.50627 |
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A quantitative analysis is performed on the decay of an unusual ring of relativistic electrons between 3 and 3.5 RE, which was observed by the Relativistic Electron Proton Telescope instrument on the Van Allen probes. The ring formed on 3 September 2012 during the main phase of a magnetic storm due to the partial depletion of the outer radiation belt for L > 3.5, and this remnant belt of relativistic electrons persisted at energies above 2 MeV, exhibiting only slow decay, until it was finally destroyed during another magnetic storm on 1 October. This long-term stability of the relativistic electron ring was associated with the rapid outward migration and maintenance of the plasmapause to distances greater than L = 4. The remnant ring was thus immune from the dynamic process, which caused rapid rebuilding of the outer radiation belt at L > 4, and was only subject to slow decay due to pitch angle scattering by plasmaspheric hiss on timescales exceeding 10\textendash20 days for electron energies above 3 MeV. At lower energies, the decay is much more rapid, consistent with the absence of a long-duration electron ring at energies below 2 MeV. Thorne, R.; Li, W.; Ni, B.; Ma, Q.; Bortnik, J.; Baker, D.; Spence, H.; Reeves, G.; Henderson, M.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Turner, D.; Angelopoulos, V.; Published by: Geophysical Research Letters Published on: 06/2013 YEAR: 2013 DOI: 10.1002/grl.50627 |