Biblio

Found 46 results
Filters: Keyword is EMIC waves  [Clear All Filters]
2019
Authors: Pinto V. A., Mourenas D., Bortnik J, Zhang X.‐J., Artemyev A. V., et al.
Title: Decay of Ultrarelativistic Remnant Belt Electrons Through Scattering by Plasmaspheric Hiss
Abstract: Ultrarelativistic electron remnant belts appear frequently following geomagnetic disturbances and are located in‐between the inner radiation belt and a reforming outer belt. As remnant belts are relatively stable, here we explore the importance of hiss and electromagnetic ion cyclotron waves in controlling the observed decay rates of remnant belt ultrarelativistic electrons in a statistical way. Using measurements from the Van Allen Probes inside the plasmasphere for 25 remnant belt events that occurred between 2012 and 2017 and that are located in the region 2.9Date: Dec-07-2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA026509 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026509
More Details
Authors: Capannolo L., Li W, Ma Q, Shen X.‐C., Zhang X.‐J., et al.
Title: Energetic Electron Precipitation: Multievent Analysis of Its Spatial Extent During EMIC Wave Activity
Abstract: Electromagnetic ion cyclotron (EMIC) waves can drive precipitation of tens of keV protons and relativistic electrons, and are a potential candidate for causing radiation belt flux dropouts. In this study, we quantitatively analyze three cases of EMIC‐driven precipitation, which occurred near the dusk sector observed by multiple Low‐Earth‐Orbiting (LEO) Polar Operational Environmental Satellites/Meteorological Operational satellite programme (POES/MetOp) satellites. During EMIC wave activity, the proton precipitation occurred from few tens of keV up to hundreds of keV, while the electron precipitation was mainly at relativistic energies. We compare observations of electron precipitation with calculations using quasi‐linear theory. For all cases, we consider the effects of other magn. . .
Date: 03/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026291 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026291
More Details
Authors: Yue Chao, Jun Chae‐Woo, Bortnik Jacob, An Xin, Ma Qianli, et al.
Title: The Relationship Between EMIC Wave Properties and Proton Distributions Based on Van Allen Probes Observations
Abstract: Plasma kinetic theory predicts that sufficiently anisotropic proton distribution will excite electromagnetic ion cyclotron (EMIC) waves, which in turn relax the proton distribution to a marginally stable state creating an upper bound on the relaxed proton anisotropy. Here, using EMIC wave observations and coincident plasma measurements made by Van Allen Probes in the inner magnetosphere, we show that the proton distributions are well constrained by this instability to a marginally stable state. Near the threshold, the probability of EMIC wave occurrence is highest, having left‐handed polarization and observed near the magnetic equator with relatively small wave normal angles, indicating that these waves are locally generated. In addition, EMIC waves are distributed in two magnetic local . . .
Date: 04/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082633 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082633
More Details
Authors: Yu Xiongdong, and Yuan Zhigang
Title: Saturation Characteristics of Parallel EMIC Waves in the Inner Magnetosphere
Abstract: In this letter, detailed evolution process of parallel electromagnetic ion cyclotron waves in the inner magnetosphere has been investigated through quasilinear theory. A new saturation has been found to occur after the usual first saturation. During the interval between these two saturations, the energy transfers from H+ band to He+ band electromagnetic ion cyclotron waves. Moreover, through a best fitting, we obtain new model parameters for the anisotropy‐beta inverse relation of hot H+, which identifies the threshold of ion cyclotron instabilities in the inner magnetosphere. In situ observations of the Van Allen Probe mission also verify these new model parameters. Therefore, our results reveal the evolution process and saturation characteristics of parallel electromagnetic ion cyclotr. . .
Date: 07/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083630 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083630
More Details
Authors: Cao Xing, Ni Binbin, Summers Danny, Shprits Yuri Y, Gu Xudong, et al.
Title: Sensitivity of EMIC Wave-Driven Scattering Loss of Ring Current Protons to Wave Normal Angle Distribution
Abstract: Electromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field‐aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of ≤10 keV protons. For >10 keV protons, the field‐aligned propagation approximation results in a pronounced underestimate of the scattering of intermediate equatorial pitch angle protons and overestimates the scattering of high equatorial pitch angle protons by orders of magnitude. Ou. . .
Date: 01/2019 Publisher: Geophysical Research Letters Pages: 590 - 598 DOI: 10.1029/2018GL081550 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL081550
More Details
Authors: Yuan Zhigang, Yu Xiongdong, Ouyang Zhihai, Yao Fei, Huang Shiyong, et al.
Title: Simultaneous trapping of EMIC and MS waves by background plasmas
Abstract: Electromagnetic ion cyclotron waves and fast magnetosonic waves are found to be simultaneously modulated by background plasma density: both kinds of waves were observed in high plasma density regions but vanished in low density regions. Theoretical analysis based on Snell's law and linear growth theory have been utilized to investigate the physical mechanisms driving such modulation. It is suggested that the modulation of fast magnetosonic waves might be due to trapping by plasma density structures, which results from a conservation of the parameter Q during their propagation. Here Q = nrsinψ, with n the refractive index, r the radial distance, and ψ the wave azimuthal angle. As for electromagnetic ion cyclotron waves, the modulation might be owed to the ion composition difference betwee. . .
Date: 02/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026149 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026149
More Details
2018
Authors: Woodger L A, Millan R M, Li Z., and Sample J G
Title: Impact of Background Magnetic Field for EMIC Wave-Driven Electron Precipitation
Abstract: Wave‐particle interaction between relativistic electrons and electromagnetic ion cyclotron (EMIC) waves is a highly debated loss process contributing to the dynamics of Earth's radiation belts. Theoretical studies show that EMIC waves can result in strong loss of relativistic electrons in the radiation belts (Summers & Thorne, 2003, https://doi.org/10.1029/2002JA009489). However, many of these studies have not been validated by observations. Li et al. (2014, https://doi.org/10.1002/2014GL062273) modeled the relativistic electron precipitation observed by Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) in a single‐event case study based on a quasi‐linear diffusion model and observations by Van Allen Probes and GOES 13. We expand upon that study to investigate th. . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025315 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025315
More Details
Authors: Remya B., Sibeck D G, Halford A J, Murphy K. R., Reeves G D, et al.
Title: Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere
Abstract: We present Van Allen Probe observations of electromagnetic ion cyclotron (EMIC) waves triggered solely due to individual substorm‐injected ions in the absence of storms or compressions of the magnetosphere during 9 August 2015. The time at which the injected ions are observed directly corresponds to the onset of EMIC waves at the location of Van Allen Probe A (L = 5.5 and 18:06 magnetic local time). The injection was also seen at geosynchronous orbit by the Geostationary Operational Environmental Satellite and Los Alamos National Laboratory spacecraft, and the westward(eastward) drift of ions(electrons) was monitored by Los Alamos National Laboratory spacecraft at different local times. The azimuthal location of the injection was determined by tracing the injection signatures backward in. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025354 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025354
More Details
Authors: Yuan Zhigang, Liu Kun, Yu Xiongdong, Yao Fei, Huang Shiyong, et al.
Title: Precipitation of radiation belt electrons by EMIC waves with conjugated observations of NOAA and Van Allen satellites
Abstract: In this letter, we present unique conjugated satellite observations of MeV relativistic electron precipitation caused by electromagnetic ion cyclotron (EMIC) waves. On the outer boundary of the plasmasphere, the Van Allen probe observed EMIC waves. At ionospheric altitudes, the NOAA 16 satellite at the footprint of Van Allen probe simultaneously detected obvious flux enhancements for precipitating >MeV radiation belt electrons, but not for precipitating MeV radiation belt electrons. Our result provides a direct magnetic conjugated observational link between in‐situ inner magnetospheric EMIC wav. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080481 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080481
More Details
Authors: Kurita S., Miyoshi Y, Shiokawa K., Higashio N., Mitani T., et al.
Title: Rapid loss of relativistic electrons by EMIC waves in the outer radiation belt observed by Arase, Van Allen Probes, and the PWING ground stations
Abstract: There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground‐based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground‐based observations constrained spatial‐temporal variations of the EMIC wave activity during the loss event. Multi‐satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantia. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080262 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080262
More Details
Authors: Noh Sung-Jun, Lee Dae-Young, Choi Cheong-Rim, Kim Hyomin, and Skoug Ruth
Title: Test of Ion Cyclotron Resonance Instability Using Proton Distributions Obtained From Van Allen Probe-A Observations
Abstract: Anisotropic velocity distributions of protons have long been considered as free energy sources for exciting electromagnetic ion cyclotron (EMIC) waves in the Earth's magnetosphere. Here we rigorously calculated the proton anisotropy parameter using proton data obtained from Van Allen Probe‐A observations. The calculations are performed for times during EMIC wave events (distinguishing the times immediately after and before EMIC wave onsets) and for times exhibiting no EMIC waves. We find that the anisotropy values are often larger immediately after EMIC wave onsets than the times just before EMIC wave onsets and the non‐EMIC wave times. The increase in anisotropy immediately after the EMIC wave onsets is rather small but discernible, such that the average increase is by ~15% relative t. . .
Date: 08/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025385 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025385
More Details
Authors: Capannolo L., Li W, Ma Q, Zhang X.-J., Redmon R. J., et al.
Title: Understanding the Driver of Energetic Electron Precipitation Using Coordinated Multisatellite Measurements
Abstract: Magnetospheric plasma waves play a significant role in ring current and radiation belt dynamics, leading to pitch angle scattering loss and/or stochastic acceleration of the particles. During a non‐storm time dropout event on 24 September 2013, intense electromagnetic ion cyclotron (EMIC) waves were detected by Van Allen Probe A (Radiation Belt Storm Probes‐A). We quantitatively analyze a conjunction event when Van Allen Probe A was located approximately along the same magnetic field line as MetOp‐01, which detected simultaneous precipitation of >30 keV protons and energetic electrons over an unexpectedly broad energy range (>~30 keV). Multipoint observations together with quasi‐linear theory provide direct evidence that the observed electron precipitation at higher energy (>~700 k. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078604 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078604
More Details
2017
Authors: Zhang X.-J., Mourenas D., Artemyev A. V., Angelopoulos V, and Thorne R M
Title: Contemporaneous EMIC and Whistler-Mode Waves: Observations and Consequences for MeV Electron Loss
Abstract: The high variability of relativistic (MeV) electron fluxes in the Earth's radiation belts is partly controlled by loss processes involving resonant interactions with electromagnetic ion cyclotron (EMIC) and whistler-mode waves. But as previous statistical models were generated independently for each wave mode, whether simultaneous electron scattering by the two wave types has global importance remains an open question. Using >3 years of simultaneous Van Allen Probes and THEMIS measurements, we explore the contemporaneous presence of EMIC and whistler-mode waves in the same L-shell, albeit at different local times, determining the distribution of wave and plasma parameters as a function of L, Kp, and AE. We derive electron lifetimes from observations and provide the first statistics of comb. . .
Date: 07/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073886 Available at: onlinelibrary.wiley.com/doi/10.1002/2017GL073886/full
More Details
Authors:
Title: EMIC wave scale size in the inner magnetosphere: Observations from the dual Van Allen Probes
Abstract: Estimating the spatial scales of electromagnetic ion cyclotron (EMIC) waves is critical for quantifying their overall scattering efficiency and effects on thermal plasma, ring current, and radiation belt particles. Using measurements from the dual Van Allen Probes in 2013–2014, we characterize the spatial and temporal extents of regions of EMIC wave activity and how these depend on local time and radial distance within the inner magnetosphere. Observations are categorized into three types—waves observed by only one spacecraft, waves measured by both spacecraft simultaneously, and waves observed by both spacecraft with some time lag. Analysis reveals that dayside (and H+ band) EMIC waves more frequently span larger spatial areas, while nightside (and He+ band) waves are more often loc. . .
Date: 01/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL072316 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL072316
More Details
Authors: Blum L. W., Bonnell J. W., Agapitov O., Paulson K., and Kletzing C.
Title: EMIC wave scale size in the inner magnetosphere: Observations from the dual Van Allen Probes
Abstract: Estimating the spatial scales of electromagnetic ion cyclotron (EMIC) waves is critical for quantifying their overall scattering efficiency and effects on thermal plasma, ring current, and radiation belt particles. Using measurements from the dual Van Allen Probes in 2013–2014, we characterize the spatial and temporal extents of regions of EMIC wave activity and how these depend on local time and radial distance within the inner magnetosphere. Observations are categorized into three types—waves observed by only one spacecraft, waves measured by both spacecraft simultaneously, and waves observed by both spacecraft with some time lag. Analysis reveals that dayside (and H+ band) EMIC waves more frequently span larger spatial areas, while nightside (and He+ band) waves are more often loc. . .
Date: 02/2017 Publisher: Geophysical Research Letters Pages: 1227 - 1233 DOI: 10.1002/2016GL072316 Available at: http://doi.wiley.com/10.1002/2016GL072316
More Details
Authors: Yu Xiongdong, Yuan Zhigang, Huang Shiyong, Wang Dedong, Li Haimeng, et al.
Title: EMIC waves covering wide L shells: MMS and Van Allen Probes observations
Abstract: During 04:45:00–08:15:00 UT on 13 September in 2015, a case of Electromagnetic ion cyclotron (EMIC) waves covering wide L shells (L = 3.6–9.4), observed by the Magnotospheric Multiscale 1 (MMS1) are reported. During the same time interval, EMIC waves observed by Van Allen Probes A (VAP-A) only occurred just outside the plasmapause. As the Van Allen Probes moved outside into a more tenuous plasma region, no intense waves were observed. Combined observations of MMS1 and VAP-A suggest that in the terrestrial magnetosphere, an appropriately dense background plasma would make contributions to the growth of EMIC waves in lower L shells, while the ion anisotropy, driven by magnetospheric compression, might play an important role in the excitation of EMIC waves in higher L shells. These EMIC w. . .
Date: 07/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA023982 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA023982/full
More Details
Authors: Tetrick S. S., Engebretson M. J., Posch J. L., Olson C. N., Smith C W, et al.
Title: Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations
Abstract: We have studied the spatial location relative to the plasmapause (PP) of the most intense electromagnetic ion cyclotron (EMIC) waves observed on Van Allen Probes A and B during their first full precession in local time. Most of these waves occurred over an L range of from -1 to +2 RE relative to the PP. Very few events occurred only within 0.1 RE of the PP, and events with a width in L of < 0.2 REoccurred both inside and outside the PP. Wave occurrence was always associated with high densities of ring current ions; plasma density gradients or enhancements were associated with some events but were not dominant factors in determining the sites of wave generation. Storm main and recovery phase events in the dusk sector were often inside the PP, and dayside events during quiet times and co. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023392 Available at: http://doi.wiley.com/10.1002/2016JA023392
More Details
Authors: Su Zhenpeng, Gao Zhonglei, Zheng Huinan, Wang Yuming, Wang Shui, et al.
Title: Rapid loss of radiation belt relativistic electrons by EMIC waves
Abstract: How relativistic electrons are lost is an important question surrounding the complex dynamics of the Earth's outer radiation belt. Radial loss to the magnetopause and local loss to the atmosphere are two main competing paradigms. Here, on the basis of the analysis of a radiation belt storm event on 27 February 2014, we present new evidence for the EMIC wave-driven local precipitation loss of relativistic electrons in the heart of the outer radiation belt. During the main phase of this storm, the radial profile of relativistic electron phase space density was quasi-monotonic, qualitatively inconsistent with the prediction of radial loss theory. The local loss at low L-shells was required to prevent the development of phase space density peak resulting from the radial loss process at high L-. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024169 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024169/full
More Details
Authors: Aseev N. A., Shprits Y Y, Drozdov A. Y., Kellerman A. C., Usanova M. E., et al.
Title: Signatures of Ultrarelativistic Electron Loss in the Heart of the Outer Radiation Belt Measured by Van Allen Probes
Abstract: Up until recently, signatures of the ultrarelativistic electron loss driven by electromagnetic ion cyclotron (EMIC) waves in the Earth's outer radiation belt have been limited to direct or indirect measurements of electron precipitation or the narrowing of normalized pitch angle distributions in the heart of the belt. In this study, we demonstrate additional observational evidence of ultrarelativistic electron loss that can be driven by resonant interaction with EMIC waves. We analyzed the profiles derived from Van Allen Probe particle data as a function of time and three adiabatic invariants between 9 October and 29 November 2012. New local minimums in the profiles are accompanied by the narrowing of normalized pitch angle distributions and ground-based detection of EMIC waves. Such a cor. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024485 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024485/full
More Details
Authors: Cho J.-H., Lee D.-Y., Noh S.-J., Kim H., Choi C. R., et al.
Title: Spatial dependence of electromagnetic ion cyclotron waves triggered by solar wind dynamic pressure enhancements
Abstract: In this paper, using the multisatellite (the Van Allen Probes and two GOES satellites) observations in the inner magnetosphere, we examine two electromagnetic ion cyclotron (EMIC) wave events that are triggered by Pdyn enhancements under prolonged northward interplanetary magnetic field quiet time preconditions. For both events, the impact of enhanced Pdyn causes EMIC waves at multiple points. However, we find a strong spatial dependence that EMIC waves due to enhanced Pdyn impact can occur at multiple points (likely globally but not necessarily everywhere) but with different wave properties. For Event 1, three satellites situated at a nearly same dawnside zone but at slightly different L shells see occurrence of EMIC waves but in different frequencies relative to local ion gyrofrequencies. . .
Date: 05/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023827 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023827/full
More Details
2016
Authors: Saikin A. A., Zhang J. -C., Smith C W, Spence H E, Torbert R B, et al.
Title: The dependence on geomagnetic conditions and solar wind dynamic pressure of the spatial distributions of EMIC waves observed by the Van Allen Probes
Abstract: A statistical examination on the spatial distributions of electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes against varying levels of geomagnetic activity (i.e., AE and SYM-H) and dynamic pressure has been performed. Measurements taken by the Electric and Magnetic Field Instrument Suite and Integrated Science for the first full magnetic local time (MLT) precession of the Van Allen Probes (September 2012–June 2014) are used to identify over 700 EMIC wave events. Spatial distributions of EMIC waves are found to vary depending on the level of geomagnetic activity and solar wind dynamic pressure. EMIC wave events were observed under quiet (AE ≤ 100 nT, 325 wave events), moderate (100 nT < AE ≤ 300 nT, 218 wave events), and disturbed (AE > 3. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022523 Available at: http://doi.wiley.com/10.1002/2016JA022523
More Details
Authors: Zhang X.-J., Li W, Ma Q, Thorne R M, Angelopoulos V, et al.
Title: Direct evidence for EMIC wave scattering of relativistic electrons in space
Abstract: Electromagnetic ion cyclotron (EMIC) waves have been proposed to cause efficient losses of highly relativistic (>1 MeV) electrons via gyroresonant interactions. Simultaneous observations of EMIC waves and equatorial electron pitch angle distributions, which can be used to directly quantify the EMIC wave scattering effect, are still very limited, however. In the present study, we evaluate the effect of EMIC waves on pitch angle scattering of ultrarelativistic (>1 MeV) electrons during the main phase of a geomagnetic storm, when intense EMIC wave activity was observed in situ (in the plasma plume region with high plasma density) on both Van Allen Probes. EMIC waves captured by Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes and on the ground across the. . .
Date: 07/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022521 Available at: http://doi.wiley.com/10.1002/2016JA022521
More Details
Authors: Blum L. W., Agapitov O., Bonnell J. W., Kletzing C., and Wygant J
Title: EMIC wave spatial and coherence scales as determined from multipoint Van Allen Probe measurements
Abstract: Electromagnetic ion cyclotron (EMIC) waves can provide a strong source of energetic electron pitch angle scattering. These waves are often quite localized, thus their spatial extent can have a large effect on their overall scattering efficiency. Using measurements from the dual Van Allen Probes, we examine four EMIC wave events observed simultaneously on the two probes at varying spacecraft separations. Correlation of both the wave amplitude and phase observed at both spacecraft is examined to estimate the active region and coherence scales of the waves. We find well-correlated wave amplitude and amplitude modulation across distances spanning hundreds to thousands of kilometers. Phase coherence persisting 30–60 s is observable during close conjunction events but is lost as spacecraft s. . .
Date: 05/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL068799 Available at: http://doi.wiley.com/10.1002/2016GL068799
More Details
Authors: Zhang Jichun, Halford Alexa J., Saikin Anthony A., Huang Chia-Lin, Spence Harlan E., et al.
Title: EMIC waves and associated relativistic electron precipitation on 25-26 January 2013
Abstract: Using measurements from the Van Allen Probes and the Balloon Array for RBSP Relativistic Electron Losses (BARREL), we perform a case study of electromagnetic ion cyclotron (EMIC) waves and associated relativistic electron precipitation (REP) observed on 25–26 January 2013. Among all the EMIC wave and REP events from the two missions, the pair of the events is the closest both in space and time. The Van Allen Probe-B detected significant EMIC waves at L = 2.1–3.9 and magnetic local time (MLT) = 21.0–23.4 for 53.5 min from 2353:00 UT, 25 January 2013. Meanwhile, BARREL-1T observed clear precipitation of relativistic electrons at L = 4.2–4.3 and MLT = 20.7–20.8 for 10.0 min from 2358 UT, 25 January 2013. Local plasma and field conditions for the excitation of the. . .
Date: 10/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022918 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022918/full
More Details
Authors: Yuan Zhigang, Yu Xiongdong, Wang Dedong, Huang Shiyong, Li Haimeng, et al.
Title: In situ evidence of the modification of the parallel propagation of EMIC waves by heated He + ions
Abstract: With observations of the Van Allen Probe B, we report in situ evidence of the modification of the parallel propagating electromagnetic ion cyclotron (EMIC) waves by heated He+ ions. In the outer boundary of the plasmasphere, accompanied with the He+ ion heating, the frequency bands of H+ and He+ for EMIC waves merged into each other, leading to the disappearance of a usual stop band between the gyrofrequency of He+ ions (ΩHe+) and the H+ cutoff frequency (ωH+co) in the cold plasma. Moreover, the dispersion relation for EMIC waves theoretically calculated with the observed plasma parameters also demonstrates that EMIC waves can indeed parallel propagate across ΩHe+. Therefore, the paper provides an in situ evidence of the modification of the parallel propagation of EMIC waves by heated H. . .
Date: 07/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022573 Available at: http://doi.wiley.com/10.1002/2016JA022573
More Details
Authors: Paulson K. W., Smith C W, Lessard M. R., Torbert R B, Kletzing C A, et al.
Title: In situ statistical observations of Pc1 pearl pulsations and unstructured EMIC waves by the Van Allen Probes
Abstract: We present here the first in situ statistical survey of structured Pc1 pearl pulsations compared with unstructured electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes spacecraft. This data set was compiled from observations spanning 8 September 2012 through 31 August 2015 and comprises over 1630 h of total EMIC wave activity, of which 291 h exhibited pearl structure. Additionally, we have identified 29 wave events demonstrating periodically oscillating wave packets, mostly about the magnetic equator, indicated by the reversal of Poynting flux along the background magnetic field. We have found several stark differences between Pc1 pearl pulsations and unstructured EMIC waves. While unstructured EMIC waves demonstrate the predicted behavior of a higher occurrence acro. . .
Date: 12/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023160 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023160/full
More Details
Authors: Zhang X.-J., Li W, Thorne R M, Angelopoulos V, Bortnik J, et al.
Title: Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes
Abstract: It has been known that electromagnetic ion cyclotron (EMIC) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of EMIC waves that usually exhibit limited spatial presence. We construct a statistical distribution of EMIC wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results show that as the ratio of plasma frequency over electron gyrofrequency increases, EMIC wave power becomes progressively dominated by the helium band. There is a pronounced dawn-dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does n. . .
Date: 12/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071158 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071158/full
More Details
Authors: Cho J.-H., Lee D.-Y., Noh S.-J., Shin D.-K., Hwang J., et al.
Title: Van Allen Probes Observations of Electromagnetic Ion Cyclotron Waves Triggered by Enhanced Solar Wind Dynamic Pressure
Abstract: Magnetospheric compression due to impact of enhanced solar wind dynamic pressure Pdyn has long been considered as one of the generation mechanisms of electromagnetic ion cyclotron (EMIC) waves. With the Van Allen Probe-A observations, we identify three EMIC wave events that are triggered by Pdyn enhancements under prolonged northward IMF quiet time preconditions. They are in contrast to one another in a few aspects. Event 1 occurs in the middle of continuously increasing Pdyn while Van Allen Probe-A is located outside the plasmapause at post-midnight and near the equator (magnetic latitude (MLAT) ~ -3o). Event 2 occurs by a sharp Pdyn pulse impact while Van Allen Probe-A is located inside the plasmapause in the dawn sector and rather away from the equator (MLAT ~ 12o). Event 3 is c. . .
Date: 09/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022841 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022841/full
More Details
Authors: Sigsbee K., Kletzing C A, Smith C W, MacDowall Robert, Spence Harlan, et al.
Title: Van Allen Probes, THEMIS, GOES, and Cluster Observations of EMIC waves, ULF pulsations, and an electron flux dropout
Abstract: We examined an electron flux dropout during the 12–14 November 2012 geomagnetic storm using observations from seven spacecraft: the two Van Allen Probes, THEMIS-A (P5), Cluster 2, and Geostationary Operational Environmental Satellite (GOES) 13, 14, and 15. The electron fluxes for energies greater than 2.0 MeV observed by GOES 13, 14, and 15 at geosynchronous orbit and by the Van Allen Probes remained at or near instrumental background levels for more than 24 hours from 12–14 November. For energies of 0.8 MeV, the GOES satellites observed two shorter intervals of reduced electron fluxes. The first interval of reduced 0.8 MeV electron fluxes on 12–13 November was associated with an interplanetary shock and a sudden impulse. Cluster, THEMIS, and GOES observed intense He+ EMIC wa. . .
Date: 01/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020877 Available at: http://doi.wiley.com/10.1002/2014JA020877
More Details
2015
Authors: Halford A J, Fraser B. J., and Morley S. K.
Title: EMIC waves and plasmaspheric and plume density: CRRES results
Abstract: Electromagnetic ion cyclotron (EMIC) waves frequently occur during geomagnetic storms, specifically during the main phase and 3–6 days following the minimum Sym − H value. EMIC waves contribute to the loss of ring current ions and radiation belt MeV electrons. Recent studies have suggested that cold plasma density structures found inside the plasmasphere and plasmaspheric plumes are important for the generation and propagation of EMIC waves. During the CRRES mission, 913 EMIC wave events and 124 geomagnetic storms were identified. In this study we compare the quiet time cold plasma density to the cold plasma density measured during EMIC wave events across different geomagnetic conditions. We found statistically that EMIC waves occurred in regions of enhanced densities. EMIC waves were,. . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 1974 - 1992 DOI: 10.1002/2014JA020338 Available at: http://doi.wiley.com/10.1002/2014JA020338
More Details
Authors: Drozdov A. Y., Shprits Y Y, Orlova K.G., Kellerman A. C., Subbotin D. A., et al.
Title: Energetic, relativistic and ultra-relativistic electrons: Comparison of long-term VERB code simulations with Van Allen Probes measurements
Abstract: In this study, we compare long-term simulations performed by the Versatile Electron Radiation Belt (VERB) code with observations from the MagEIS and REPT instruments on the Van Allen Probes satellites. The model takes into account radial, energy, pitch-angle and mixed diffusion, losses into the atmosphere, and magnetopause shadowing. We consider the energetic (>100 keV), relativistic (~0.5-1 MeV) and ultra-relativistic (>2 MeV) electrons. One year of relativistic electron measurements (μ=700 MeV/G) from October 1, 2012 to October 1, 2013, are well reproduced by the simulation during varying levels of geomagnetic activity. However, for ultra-relativistic energies (μ=3500 MeV/G), the VERB code simulation overestimates electron fluxes and Phase Space Density. These results indicate that an . . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020637 Available at: http://doi.wiley.com/10.1002/2014JA020637
More Details
Authors: Bin Kang Suk-, Min Kyoung-Wook, Fok Mei-Ching, Hwang Junga, and Choi Cheong-Rim
Title: Estimation of pitch angle diffusion rates and precipitation time scales of electrons due to EMIC waves in a realistic field model
Abstract: Electromagnetic ion cyclotron (EMIC) waves are closely related to precipitating loss of relativistic electrons in the radiation belts, and thereby, a model of the radiation belts requires inclusion of the pitch angle diffusion caused by EMIC waves. We estimated the pitch angle diffusion rates and the corresponding precipitation time scales caused by H and He band EMIC waves using the Tsyganenko 04 (T04) magnetic field model at their probable regions in terms of geomagnetic conditions. The results correspond to enhanced pitch angle diffusion rates and reduced precipitation time scales compared to those based on the dipole model, up to several orders of magnitude for storm times. While both the plasma density and the magnetic field strength varied in these calculations, the reduction of the . . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 8529 - 8546 DOI: 10.1002/2014JA020644 Available at: http://doi.wiley.com/10.1002/2014JA020644http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2014JA020644
More Details
Authors: Rodger Craig J., Hendry Aaron T., Clilverd Mark A., Kletzing Craig A., Brundell James B., et al.
Title: High-resolution in situ observations of electron precipitation-causing EMIC waves
Abstract: Electromagnetic ion cyclotron (EMIC) waves are thought to be important drivers of energetic electron losses from the outer radiation belt through precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering-driven losses from these waves has been recognized for more than four decades, there have been limited experimental precipitation observations to support this concept. We have combined satellite-based observations of the characteristics of EMIC waves, with satellite and ground-based observations of the EMIC-induced electron precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size, and energy range of EMIC-induced electron precipitation inferred from coincident pr. . .
Date: 11/2015 Publisher: Geophysical Research Letters Pages: 9633 - 9641 DOI: 10.1002/grl.v42.2210.1002/2015GL066581 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015GL066581/full
More Details
Authors: Yu Xiongdong, Yuan Zhigang, Wang Dedong, Li Haimeng, Huang Shiyong, et al.
Title: In situ observations of EMIC waves in O + band by the Van Allen Probe A
Abstract: Through polarization and spectra analysis of the magnetic field observed by the Van Allen Probe A, we present two typical cases of O+ band EMIC waves in the outer plasmasphere or plasma trough. Although such O+ band EMIC waves are rarely observed, 18 different events of O+ band EMIC waves (16 events in the outer plasmasphere and 2 events in the plasma trough) are found from September 2012 to August 2014 with observations of the Van Allen Probe A. We find that the preferred region for the occurrence of O+ band EMIC waves is in L = 2-5 and MLT = 03-13, 19-20, which is in accordance with the occurrence region of O+ ion torus. Therefore, our result suggests that the O+ ion torus in the outer plasmasphere during geomagnetic activities should play an important role in the generation of EMIC wave. . .
Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL063250 Available at: http://doi.wiley.com/10.1002/2015GL063250
More Details
Authors: Blum L. W., Halford A., Millan R., Bonnell J. W., Goldstein J, et al.
Title: Observations of coincident EMIC wave activity and duskside energetic electron precipitation on 18-19 January 2013
Abstract: Electromagnetic ion cyclotron (EMIC) waves have been suggested to be a cause of radiation belt electron loss to the atmosphere. Here simultaneous, magnetically conjugate measurements are presented of EMIC wave activity, measured at geosynchronous orbit and on the ground, and energetic electron precipitation, seen by the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) campaign, on two consecutive days in January 2013. Multiple bursts of precipitation were observed on the duskside of the magnetosphere at the end of 18 January and again late on 19 January, concurrent with particle injections, substorm activity, and enhanced magnetospheric convection. The structure, timing, and spatial extent of the waves are compared to those of the precipitation during both days to det. . .
Date: 07/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL065245 Available at: http://doi.wiley.com/10.1002/2015GL065245
More Details
Authors: Saikin A. A., Zhang J.-C., Allen R.C., Smith C W, Kistler L. M., et al.
Title: The occurrence and wave properties of H + -, He + -, and O + -band EMIC waves observed by the Van Allen Probes
Abstract: We perform a statistical study of electromagnetic ion cyclotron (EMIC) waves detected by the Van Allen Probes mission to investigate the spatial distribution of their occurrence, wave power, ellipticity, and normal angle. The Van Allen Probes have been used which allow us to explore the inner magnetosphere (1.1 to 5.8 Re). Magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science onboard the Van Allen Probes are used to identify EMIC wave events for the first 22 months of the mission operation (8 September 2012 – 30 June 2014). EMIC waves are examined in H+-, He+-, and O+-bands. Over 700 EMIC wave events have been identified over the three different wave bands (265 H+-band events, 438 He+-band events, and 68 O+-band events). EMIC wave events. . .
Date: 09/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021358 Available at: http://doi.wiley.com/10.1002/2015JA021358
More Details
Authors: Ni Binbin, Cao Xing, Zou Zhengyang, Zhou Chen, Gu Xudong, et al.
Title: Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales
Abstract: To improve our understanding of the role of electromagnetic ion cyclotron (EMIC) waves in radiation belt electron dynamics, we perform a comprehensive analysis of EMIC wave-induced resonant scattering of outer zone relativistic (>0.5 MeV) electrons and resultant electron loss time scales with respect to EMIC wave band, L shell, and wave normal angle model. The results demonstrate that while H+-band EMIC waves dominate the scattering losses of ~1–4 MeV outer zone relativistic electrons, it is He+-band and O+-band waves that prevail over the pitch angle diffusion of ultrarelativistic electrons at higher energies. Given the wave amplitude, EMIC waves at higher L shells tend to resonantly interact with a larger population of outer zone relativistic electrons and drive their pitch angle s. . .
Date: 09/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 7357 - 7373 DOI: 10.1002/2015JA021466 Available at: http://doi.wiley.com/10.1002/2015JA021466http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021466
More Details
Authors: Lessard Marc R., Lindgren Erik A., Engebretson Mark J, and Weaver Carol
Title: Solar cycle dependence of ion cyclotron wave frequencies
Abstract: Electromagnetic ion cyclotron (EMIC) waves have been studied for decades, though remain a fundamentally important topic in heliospheric physics. The connection of EMIC waves to the scattering of energetic particles from Earth's radiation belts is one ofmany topics that motivate the need for a deeper understanding of characteristics and occurrence distributions of the waves. In this study, we show that EMIC wave frequencies, as observed at Halley Station in Antarctica from 2008 through 2012, increase by approximately 60% from a minimum in 2009 to the end of 2012. Assuming that these waves are excited in the vicinity of the plasmapause, the change in Kp in going from solar minimum to near solar maximum would drive increased plasmapause erosion, potentially shifting the generation region of t. . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020791 Available at: http://doi.wiley.com/10.1002/2014JA020791
More Details
Authors: Wang Dedong, Yuan Zhigang, Yu Xiongdong, Deng Xiaohua, Zhou Meng, et al.
Title: Statistical characteristic of EMIC waves: Van Allen Probe observations
Abstract: Utilizing the data from the magnetometer instrument which is a part of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument suite onboard the Van Allen Probe A from Sep. 2012 to Apr. 2014, when the apogee of the satellite has passed all the MLT sectors, we obtain the statistical distribution characteristic of EMIC waves in the inner magnetosphere over all local times from L=3 to L=6. Compared with the previous statistical results about EMIC waves, the occurrence rates of EMIC waves distribute relatively uniform in the MLT sectors in lower L-shells. On the other hand, in higher L-shells, there are indeed some peaks of the occurrence rate for the EMIC waves, especially in the noon, dusk and night sectors. EMIC waves appear at lower L-shells in the dawn. . .
Date: 05/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021089 Available at: http://doi.wiley.com/10.1002/2015JA021089
More Details
Authors: Allen R. C., Zhang J. -C., Kistler L. M., Spence H E, Lin R. -L., et al.
Title: A statistical study of EMIC waves observed by Cluster: 1. Wave properties
Abstract: Electromagnetic ion cyclotron (EMIC) waves are an important mechanism for particle energization and losses inside the magnetosphere. In order to better understand the effects of these waves on particle dynamics, detailed information about the occurrence rate, wave power, ellipticity, normal angle, energy propagation angle distributions, as well as local plasma parameters are required. Previous statistical studies have used in situ observations to investigate the distribution of these parameters in the MLT-L frame within a limited MLAT range. In this study, we present a statistical analysis of EMIC wave properties using ten years (2001–2010) of data from Cluster, totaling 25,431 minutes of wave activity. Due to the polar orbit of Cluster, we are able to investigate EMIC waves at all MLATs. . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021333 Available at: http://doi.wiley.com/10.1002/2015JA021333
More Details
Authors: Engebretson M. J., Posch J. L., Wygant J R, Kletzing C A, Lessard M. R., et al.
Title: Van Allen probes, NOAA, GOES, and ground observations of an intense EMIC wave event extending over 12 hours in MLT
Abstract: Although most studies of the effects of EMIC waves on Earth's outer radiation belt have focused on events in the afternoon sector in the outer plasmasphere or plume region, strong magnetospheric compressions provide an additional stimulus for EMIC wave generation across a large range of local times and L shells. We present here observations of the effects of a wave event on February 23, 2014 that extended over 8 hours in UT and over 12 hours in local time, stimulated by a gradual 4-hour rise and subsequent sharp increases in solar wind pressure. Large-amplitude linearly polarized hydrogen band EMIC waves (up to 25 nT p-p) appeared for over 4 hours at both Van Allen Probes, from late morning through local noon, when these spacecraft were outside the plasmapause, with densities ~5-20 cm-3. W. . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021227 Available at: http://doi.wiley.com/10.1002/2015JA021227
More Details
2014
Authors: Kersten Tobias, Horne Richard B, Glauert Sarah A, Meredith Nigel P, Fraser Brian J., et al.
Title: Electron losses from the radiation belts caused by EMIC waves
Abstract: Electromagnetic Ion Cyclotron (EMIC) waves cause electron loss in the radiation belts by resonating with high-energy electrons at energies greater than about 500 keV. However, their effectiveness has not been fully quantified. Here we determine the effectiveness of EMIC waves by using wave data from the fluxgate magnetometer on CRRES to calculate bounce-averaged pitch angle and energy diffusion rates for L*=3.5–7 for five levels of Kp between 12 and 18 MLT. To determine the electron loss, EMIC diffusion rates were included in the British Antarctic Survey Radiation Belt Model together with whistler mode chorus, plasmaspheric hiss, and radial diffusion. By simulating a 100 day period in 1990, we show that EMIC waves caused a significant reduction in the electron flux for energies greater t. . .
Date: 11/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020366 Available at: http://doi.wiley.com/10.1002/2014JA020366
More Details
Authors: Nishimura Y., Bortnik J, Li W, Lyons L R, Donovan E. F., et al.
Title: Evolution of nightside subauroral proton aurora caused by transient plasma sheet flows
Abstract: While nightside subauroral proton aurora shows rapid temporal variations, the cause of this variability has rarely been investigated. Using well-coordinated observations by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imagers, THEMIS satellites in the equatorial magnetosphere, and the low-altitude NOAA 17 satellite, we examined the rapid temporal evolution of subauroral proton aurora in the premidnight sector. An isolated proton aurora occurred soon after an auroral poleward boundary intensification that was followed by an auroral streamer reaching the equatorward boundary of the auroral oval. Three THEMIS satellites in the magnetotail detected flow bursts and one of the THEMIS satellites in the outer plasmasphere observed a ring current injectio. . .
Date: 07/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 5295 - 5304 DOI: 10.1002/2014JA020029 Available at: http://doi.wiley.com/10.1002/2014JA020029
More Details
Authors: Li Zan, Millan Robyn M., Hudson Mary K, Woodger Leslie A., Smith David M., et al.
Title: Investigation of EMIC wave scattering as the cause for the BARREL January 17, 2013 relativistic electron precipitation event: a quantitative comparison of simulation with observations
Abstract: Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the BARREL balloons, and was magnetically mapped close to GOES-13. We simulate the relativistic electron pitch-angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES-13 and the Van Allen Probes. We show that the count rate, the energy distribution and the time variation of the simulated precipitation all agree very well with the balloon observations, suggesting that EMIC wave scattering was likely the cause for the precipitation event. The event reported here is . . .
Date: 12/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062273 Available at: http://doi.wiley.com/10.1002/2014GL062273
More Details
Authors: Lee Justin H., and Angelopoulos Vassilis
Title: Observations and modeling of EMIC wave properties in the presence of multiple ion species as function of magnetic local time
Abstract: Electromagnetic ion cyclotron (EMIC) wave generation and propagation in Earth's magnetosphere depend on readily measurable hot (a few to tens of keV) plasma sheet ions, elusive plasmaspheric or ionospheric cold (sub-eV to a few eV) ions, and partially heated warm ions (tens to hundreds of eV). Previous work has assumed all low-energy ions are cold and not considered possible effects of warm ions. Using measurements by multiple Time History of Events and Macroscale Interactions during Substorms spacecraft, we analyze four typical EMIC wave events in the four magnetic local time sectors and consider the properties of both cold and warm ions supplied from previous statistical studies to interpret the wave observations using linear theory. As expected, we find that dusk EMIC waves grow due to . . .
Date: 11/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020469 Available at: http://doi.wiley.com/10.1002/2014JA020469
More Details
2012
Authors: Min Kyungguk, Lee Jeongwoo, Keika Kunihiro, and Li W
Title: Global distribution of EMIC waves derived from THEMIS observations
Abstract: [1] Electromagnetic ion cyclotron (EMIC) waves play an important role in magnetospheric dynamics and their global distribution has been of great interest. This paper presents the distribution of EMIC waves over a broader range than ever before, as enabled by observations with the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft from 2007 to 2010. Our major findings are: (1) There are two major peaks in the EMIC wave occurrence probability. One is at dusk and 8–12 RE where the helium band dominates the hydrogen band waves. The other is at dawn and 10–12 RE where the hydrogen band dominates the helium band waves. (2) In terms of wave spectral power the dusk events are stronger (≈10 nT2/Hz) than the dawn events (≈3 nT2/Hz). (3) The dawn . . .
Date: 05/2012 Publisher: Journal of Geophysical Research DOI: 10.1029/2012JA017515
More Details