Bibliography
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Found 4151 entries in the Bibliography.
Showing entries from 3601 through 3650
| 2014 |
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On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50\% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (>2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased >90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi-MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere. Foster, J.; Erickson, P.; Baker, D.; Claudepierre, S.; Kletzing, C.; Kurth, W.; Reeves, G.; Thaller, S.; Spence, H.; Shprits, Y; Wygant, J.; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058438 |
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On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50\% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (>2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased >90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi-MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere. Foster, J.; Erickson, P.; Baker, D.; Claudepierre, S.; Kletzing, C.; Kurth, W.; Reeves, G.; Thaller, S.; Spence, H.; Shprits, Y; Wygant, J.; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058438 |
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On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50\% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (>2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased >90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi-MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere. Foster, J.; Erickson, P.; Baker, D.; Claudepierre, S.; Kletzing, C.; Kurth, W.; Reeves, G.; Thaller, S.; Spence, H.; Shprits, Y; Wygant, J.; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058438 |
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On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50\% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (>2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased >90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi-MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere. Foster, J.; Erickson, P.; Baker, D.; Claudepierre, S.; Kletzing, C.; Kurth, W.; Reeves, G.; Thaller, S.; Spence, H.; Shprits, Y; Wygant, J.; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058438 |
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On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50\% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (>2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased >90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi-MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere. Foster, J.; Erickson, P.; Baker, D.; Claudepierre, S.; Kletzing, C.; Kurth, W.; Reeves, G.; Thaller, S.; Spence, H.; Shprits, Y; Wygant, J.; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058438 |
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On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50\% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (>2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased >90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi-MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere. Foster, J.; Erickson, P.; Baker, D.; Claudepierre, S.; Kletzing, C.; Kurth, W.; Reeves, G.; Thaller, S.; Spence, H.; Shprits, Y; Wygant, J.; Published by: Geophysical Research Letters Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013GL058438 |
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The physics of the creation, loss, and transport of radiation belt particles is intimately connected to the electric and magnetic fields which mediate these processes. A large range of field and particle interactions are involved in this physics from large-scale ring current ion and magnetic field dynamics to microscopic kinetic interactions of whistler-mode chorus waves with energetic electrons. To measure these kinds of radiation belt interactions, NASA implemented the two-satellite Van Allen Probes mission. As part of the mission, the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) investigation is an integrated set of instruments consisting of a tri-axial fluxgate magnetometer (MAG) and a Waves instrument which includes a tri-axial search coil magnetometer (MSC). These wave measurements include AC electric and magnetic fields from 10Hz to 400 kHz. Published by: Published on: 01/2014 YEAR: 2014 DOI: 10.1109/USNC-URSI-NRSM.2014.6928090 Magnetic field measurement; magnetic fields; Magnetic flux; Van Allen Probes |
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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 |
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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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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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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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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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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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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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Energetic electron precipitation (EEP) impacts the chemistry of the middle atmosphere with growing evidence of coupling to surface temperatures at high latitudes. To better understand this link, it is essential to have realistic observations to properly characterize precipitation and which can be incorporated into chemistry-climate models. The Polar-orbiting Operational Environmental Satellite (POES) detectors measure precipitating particles but only integral fluxes and only in a fraction of the bounce loss cone. Ground-based riometers respond to precipitation from the whole bounce loss cone; they measure the cosmic radio noise absorption (CNA), a qualitative proxy with scant direct information on the energy flux of EEP. POES observations should have a direct relationship with ΔCNA and comparing the two will clarify their utility in studies of atmospheric change. We determined ionospheric changes produced by the EEP measured by the POES spacecraft in ~250 overpasses of an imaging riometer in northern Finland. The ΔCNA modeled from the POES data is 10\textendash15 times less than the observed ΔCNA when the >30 keV flux is reported as <106 cm-2 s-1 sr-1. Above this level, there is relatively good agreement between the space-based and ground-based measurements. The discrepancy occurs mostly during periods of low geomagnetic activity, and we contend that weak diffusion is dominating the pitch angle scattering into the bounce loss cone at these times. A correction to the calculation using measurements of the trapped flux considerably reduces the discrepancy and provides further support to our hypothesis that weak diffusion leads to underestimates of the EEP. Rodger, Craig; Kavanagh, Andrew; Clilverd, Mark; Marple, Steve; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019439 |
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Energetic electron precipitation (EEP) impacts the chemistry of the middle atmosphere with growing evidence of coupling to surface temperatures at high latitudes. To better understand this link, it is essential to have realistic observations to properly characterize precipitation and which can be incorporated into chemistry-climate models. The Polar-orbiting Operational Environmental Satellite (POES) detectors measure precipitating particles but only integral fluxes and only in a fraction of the bounce loss cone. Ground-based riometers respond to precipitation from the whole bounce loss cone; they measure the cosmic radio noise absorption (CNA), a qualitative proxy with scant direct information on the energy flux of EEP. POES observations should have a direct relationship with ΔCNA and comparing the two will clarify their utility in studies of atmospheric change. We determined ionospheric changes produced by the EEP measured by the POES spacecraft in ~250 overpasses of an imaging riometer in northern Finland. The ΔCNA modeled from the POES data is 10\textendash15 times less than the observed ΔCNA when the >30 keV flux is reported as <106 cm-2 s-1 sr-1. Above this level, there is relatively good agreement between the space-based and ground-based measurements. The discrepancy occurs mostly during periods of low geomagnetic activity, and we contend that weak diffusion is dominating the pitch angle scattering into the bounce loss cone at these times. A correction to the calculation using measurements of the trapped flux considerably reduces the discrepancy and provides further support to our hypothesis that weak diffusion leads to underestimates of the EEP. Rodger, Craig; Kavanagh, Andrew; Clilverd, Mark; Marple, Steve; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019439 |
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Energetic electron precipitation (EEP) impacts the chemistry of the middle atmosphere with growing evidence of coupling to surface temperatures at high latitudes. To better understand this link, it is essential to have realistic observations to properly characterize precipitation and which can be incorporated into chemistry-climate models. The Polar-orbiting Operational Environmental Satellite (POES) detectors measure precipitating particles but only integral fluxes and only in a fraction of the bounce loss cone. Ground-based riometers respond to precipitation from the whole bounce loss cone; they measure the cosmic radio noise absorption (CNA), a qualitative proxy with scant direct information on the energy flux of EEP. POES observations should have a direct relationship with ΔCNA and comparing the two will clarify their utility in studies of atmospheric change. We determined ionospheric changes produced by the EEP measured by the POES spacecraft in ~250 overpasses of an imaging riometer in northern Finland. The ΔCNA modeled from the POES data is 10\textendash15 times less than the observed ΔCNA when the >30 keV flux is reported as <106 cm-2 s-1 sr-1. Above this level, there is relatively good agreement between the space-based and ground-based measurements. The discrepancy occurs mostly during periods of low geomagnetic activity, and we contend that weak diffusion is dominating the pitch angle scattering into the bounce loss cone at these times. A correction to the calculation using measurements of the trapped flux considerably reduces the discrepancy and provides further support to our hypothesis that weak diffusion leads to underestimates of the EEP. Rodger, Craig; Kavanagh, Andrew; Clilverd, Mark; Marple, Steve; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019439 |
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The energy spectra of energetic electron precipitation from the radiation belts are studied in order to improve our understanding of the influence of radiation belt processes. The Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) microsatellite electron flux instrument is comparatively unusual in that it has very high energy resolution (128 channels with 17.9 keV widths in normal survey mode), which lends itself to this type of spectral analysis. Here electron spectra from DEMETER have been analyzed from all six years of its operation, and three fit types (power law, exponential, and kappa-type) have been applied to the precipitating flux observations. We show that the power law fit consistently provides the best representation of the flux and that the kappa-type is rarely valid. We also provide estimated uncertainties in the flux for this instrument as a function of energy. Average power law gradients for nontrapped particles have been determined for geomagnetically nondisturbed periods to get a typical global behavior of the spectra in the inner radiation belt, slot region, and outer radiation belt. Power law spectral gradients in the outer belt are typically -2.5 during quiet periods, changing to a softer spectrum of \~-3.5 during geomagnetic storms. The inner belt does the opposite, hardening from -4 during quiet times to \~-3 during storms. Typical outer belt e-folding values are \~200 keV, dropping to \~150 keV during geomagnetic storms, while the inner belt e-folding values change from \~120 keV to >200 keV. Analysis of geomagnetic storm periods show that the precipitating flux enhancements evident from such storms take approximately 13 days to return to normal values for the outer belt and slot region and approximately 10 days for the inner belt. Whittaker, Ian; Gamble, Rory; Rodger, Craig; Clilverd, Mark; Sauvaud, \; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019228 |
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The energy spectra of energetic electron precipitation from the radiation belts are studied in order to improve our understanding of the influence of radiation belt processes. The Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) microsatellite electron flux instrument is comparatively unusual in that it has very high energy resolution (128 channels with 17.9 keV widths in normal survey mode), which lends itself to this type of spectral analysis. Here electron spectra from DEMETER have been analyzed from all six years of its operation, and three fit types (power law, exponential, and kappa-type) have been applied to the precipitating flux observations. We show that the power law fit consistently provides the best representation of the flux and that the kappa-type is rarely valid. We also provide estimated uncertainties in the flux for this instrument as a function of energy. Average power law gradients for nontrapped particles have been determined for geomagnetically nondisturbed periods to get a typical global behavior of the spectra in the inner radiation belt, slot region, and outer radiation belt. Power law spectral gradients in the outer belt are typically -2.5 during quiet periods, changing to a softer spectrum of \~-3.5 during geomagnetic storms. The inner belt does the opposite, hardening from -4 during quiet times to \~-3 during storms. Typical outer belt e-folding values are \~200 keV, dropping to \~150 keV during geomagnetic storms, while the inner belt e-folding values change from \~120 keV to >200 keV. Analysis of geomagnetic storm periods show that the precipitating flux enhancements evident from such storms take approximately 13 days to return to normal values for the outer belt and slot region and approximately 10 days for the inner belt. Whittaker, Ian; Gamble, Rory; Rodger, Craig; Clilverd, Mark; Sauvaud, \; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019228 |
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The energy spectra of energetic electron precipitation from the radiation belts are studied in order to improve our understanding of the influence of radiation belt processes. The Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) microsatellite electron flux instrument is comparatively unusual in that it has very high energy resolution (128 channels with 17.9 keV widths in normal survey mode), which lends itself to this type of spectral analysis. Here electron spectra from DEMETER have been analyzed from all six years of its operation, and three fit types (power law, exponential, and kappa-type) have been applied to the precipitating flux observations. We show that the power law fit consistently provides the best representation of the flux and that the kappa-type is rarely valid. We also provide estimated uncertainties in the flux for this instrument as a function of energy. Average power law gradients for nontrapped particles have been determined for geomagnetically nondisturbed periods to get a typical global behavior of the spectra in the inner radiation belt, slot region, and outer radiation belt. Power law spectral gradients in the outer belt are typically -2.5 during quiet periods, changing to a softer spectrum of \~-3.5 during geomagnetic storms. The inner belt does the opposite, hardening from -4 during quiet times to \~-3 during storms. Typical outer belt e-folding values are \~200 keV, dropping to \~150 keV during geomagnetic storms, while the inner belt e-folding values change from \~120 keV to >200 keV. Analysis of geomagnetic storm periods show that the precipitating flux enhancements evident from such storms take approximately 13 days to return to normal values for the outer belt and slot region and approximately 10 days for the inner belt. Whittaker, Ian; Gamble, Rory; Rodger, Craig; Clilverd, Mark; Sauvaud, \; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019228 |
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The energy spectra of energetic electron precipitation from the radiation belts are studied in order to improve our understanding of the influence of radiation belt processes. The Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) microsatellite electron flux instrument is comparatively unusual in that it has very high energy resolution (128 channels with 17.9 keV widths in normal survey mode), which lends itself to this type of spectral analysis. Here electron spectra from DEMETER have been analyzed from all six years of its operation, and three fit types (power law, exponential, and kappa-type) have been applied to the precipitating flux observations. We show that the power law fit consistently provides the best representation of the flux and that the kappa-type is rarely valid. We also provide estimated uncertainties in the flux for this instrument as a function of energy. Average power law gradients for nontrapped particles have been determined for geomagnetically nondisturbed periods to get a typical global behavior of the spectra in the inner radiation belt, slot region, and outer radiation belt. Power law spectral gradients in the outer belt are typically -2.5 during quiet periods, changing to a softer spectrum of \~-3.5 during geomagnetic storms. The inner belt does the opposite, hardening from -4 during quiet times to \~-3 during storms. Typical outer belt e-folding values are \~200 keV, dropping to \~150 keV during geomagnetic storms, while the inner belt e-folding values change from \~120 keV to >200 keV. Analysis of geomagnetic storm periods show that the precipitating flux enhancements evident from such storms take approximately 13 days to return to normal values for the outer belt and slot region and approximately 10 days for the inner belt. Whittaker, Ian; Gamble, Rory; Rodger, Craig; Clilverd, Mark; Sauvaud, \; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019228 |
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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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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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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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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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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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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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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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Huge numbers of double layers carrying electric fields parallel to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth\textquoterights outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230 000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1 000 000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer speed of 3100 km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double layers may result from a new electron acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects. Mozer, F.; Bale, S.; Bonnell, J; Chaston, C.; Roth, I.; Wygant, J.; Published by: Physical Review Letters Published on: 12/2013 YEAR: 2013 DOI: 10.1103/PhysRevLett.111.235002 |
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Huge numbers of double layers carrying electric fields parallel to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth\textquoterights outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230 000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1 000 000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer speed of 3100 km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double layers may result from a new electron acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects. Mozer, F.; Bale, S.; Bonnell, J; Chaston, C.; Roth, I.; Wygant, J.; Published by: Physical Review Letters Published on: 12/2013 YEAR: 2013 DOI: 10.1103/PhysRevLett.111.235002 |
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Huge numbers of double layers carrying electric fields parallel to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth\textquoterights outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230 000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1 000 000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer speed of 3100 km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double layers may result from a new electron acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects. Mozer, F.; Bale, S.; Bonnell, J; Chaston, C.; Roth, I.; Wygant, J.; Published by: Physical Review Letters Published on: 12/2013 YEAR: 2013 DOI: 10.1103/PhysRevLett.111.235002 |
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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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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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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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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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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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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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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 radiation belts and plasma in the Earth\textquoterights magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper. Ginet, G.; textquoterightBrien, T.; Huston, S.; Johnston, W.; Guild, T.; Friedel, R.; Lindstrom, C.; Roth, C.; Whelan, P.; Quinn, R.; Madden, D.; Morley, S.; Su, Yi-Jiun; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9964-y |
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The radiation belts and plasma in the Earth\textquoterights magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper. Ginet, G.; textquoterightBrien, T.; Huston, S.; Johnston, W.; Guild, T.; Friedel, R.; Lindstrom, C.; Roth, C.; Whelan, P.; Quinn, R.; Madden, D.; Morley, S.; Su, Yi-Jiun; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9964-y |
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The radiation belts and plasma in the Earth\textquoterights magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper. Ginet, G.; textquoterightBrien, T.; Huston, S.; Johnston, W.; Guild, T.; Friedel, R.; Lindstrom, C.; Roth, C.; Whelan, P.; Quinn, R.; Madden, D.; Morley, S.; Su, Yi-Jiun; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9964-y |
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The radiation belts and plasma in the Earth\textquoterights magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper. Ginet, G.; textquoterightBrien, T.; Huston, S.; Johnston, W.; Guild, T.; Friedel, R.; Lindstrom, C.; Roth, C.; Whelan, P.; Quinn, R.; Madden, D.; Morley, S.; Su, Yi-Jiun; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9964-y |
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The radiation belts and plasma in the Earth\textquoterights magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper. Ginet, G.; textquoterightBrien, T.; Huston, S.; Johnston, W.; Guild, T.; Friedel, R.; Lindstrom, C.; Roth, C.; Whelan, P.; Quinn, R.; Madden, D.; Morley, S.; Su, Yi-Jiun; Published by: Space Science Reviews Published on: 11/2013 YEAR: 2013 DOI: 10.1007/s11214-013-9964-y |