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Title: Direct evidence for EMIC wave scattering of relativistic electrons in space: EMIC-Driven Electron Losses 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 Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) are also used to infer their magnetic local time (MLT) coverage. From the observed EMIC wave spectra and local plasma parameters, we compute wave diffusion rates and model the evolution of electron pitch angle distributions. In conclusion, by comparing model results with local observations of pitch angle distributions, we show direct, quantitative evidence of EMIC wave-driven relativistic electron losses in the Earth’s outer radiation belt.

Authors:
 [1];  [2]; ORCiD logo [2];  [2];  [3];  [2];  [4];  [5];  [5];  [5];  [6]; ORCiD logo [7];  [8];  [9];  [9]
  1. Univ. of California, Los Angeles, CA (United States). Dept. of Atmospheric and Oceanic Sciences; Univ. of California, Los Angeles, CA (United States). Dept. of Earth, Planetary, and Space Sciences and Inst. of Geophysics and Space Physics
  2. Univ. of California, Los Angeles, CA (United States). Dept. of Atmospheric and Oceanic Sciences
  3. Univ. of California, Los Angeles, CA (United States). Dept. of Earth, Planetary, and Space Sciences and Inst. of Geophysics and Space Physics
  4. Univ. of Texas at Dallas, Richardson, TX (United States). Dept. of Physics
  5. Univ. of Iowa, Iowa City, IA (United States). Dept. of Physics and Astronomy
  6. Univ. of Colorado, Boulder, CO (United States). Lab. for Atmospheric and Space Research
  7. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); New Mexico Consortium, Los Alamos, NM (United States). Space Sciences Division
  8. Univ. of New Hampshire, Durham, NH (United States). Inst. for the Study of Earth, Oceans, and Space
  9. Aerospace Corporation, Los Angeles, CA (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Aeronautic and Space Administration (NASA); USDOE
OSTI Identifier:
1402611
Report Number(s):
LA-UR-16-23135
Journal ID: ISSN 2169-9380; TRN: US1703009
Grant/Contract Number:
AC52-06NA25396; 967399; 921647; NAS5-01072; NNX15AI96G; NNX15AF61G; NNX11AR64G; NNX13AI61G; NNX14AI18G; FA9550-15-1-0158; AGS 1564510
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Space Physics
Additional Journal Information:
Journal Volume: 121; Journal Issue: 7; Journal ID: ISSN 2169-9380
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Heliospheric and Magnetospheric Physics; EMIC waves; relativistic electron loss; wave-particle interaction; Fokker-Planck equation; electron precipitation; equatorial pitch angle distribution

Citation Formats

Zhang, X. -J., Li, W., Ma, Q., Thorne, R. M., Angelopoulos, V., Bortnik, J., Chen, L., Kletzing, C. A., Kurth, W. S., Hospodarsky, G. B., Baker, D. N., Reeves, G. D., Spence, H. E., Blake, J. B., and Fennell, J. F. Direct evidence for EMIC wave scattering of relativistic electrons in space: EMIC-Driven Electron Losses in Space. United States: N. p., 2016. Web. doi:10.1002/2016JA022521.
Zhang, X. -J., Li, W., Ma, Q., Thorne, R. M., Angelopoulos, V., Bortnik, J., Chen, L., Kletzing, C. A., Kurth, W. S., Hospodarsky, G. B., Baker, D. N., Reeves, G. D., Spence, H. E., Blake, J. B., & Fennell, J. F. Direct evidence for EMIC wave scattering of relativistic electrons in space: EMIC-Driven Electron Losses in Space. United States. doi:10.1002/2016JA022521.
Zhang, X. -J., Li, W., Ma, Q., Thorne, R. M., Angelopoulos, V., Bortnik, J., Chen, L., Kletzing, C. A., Kurth, W. S., Hospodarsky, G. B., Baker, D. N., Reeves, G. D., Spence, H. E., Blake, J. B., and Fennell, J. F. 2016. "Direct evidence for EMIC wave scattering of relativistic electrons in space: EMIC-Driven Electron Losses in Space". United States. doi:10.1002/2016JA022521. https://www.osti.gov/servlets/purl/1402611.
@article{osti_1402611,
title = {Direct evidence for EMIC wave scattering of relativistic electrons in space: EMIC-Driven Electron Losses in Space},
author = {Zhang, X. -J. and Li, W. and Ma, Q. and Thorne, R. M. and Angelopoulos, V. and Bortnik, J. and Chen, L. and Kletzing, C. A. and Kurth, W. S. and Hospodarsky, G. B. and Baker, D. N. and Reeves, G. D. and Spence, H. E. and Blake, J. B. and Fennell, J. F.},
abstractNote = {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 Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) are also used to infer their magnetic local time (MLT) coverage. From the observed EMIC wave spectra and local plasma parameters, we compute wave diffusion rates and model the evolution of electron pitch angle distributions. In conclusion, by comparing model results with local observations of pitch angle distributions, we show direct, quantitative evidence of EMIC wave-driven relativistic electron losses in the Earth’s outer radiation belt.},
doi = {10.1002/2016JA022521},
journal = {Journal of Geophysical Research. Space Physics},
number = 7,
volume = 121,
place = {United States},
year = 2016,
month = 7
}

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  • 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 Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) balloons and was magnetically mapped close to Geostationary Operational Environmental Satellite (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,more » 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 the first balloon REP event with closely conjugate EMIC wave observations, and our study employs the most detailed quantitative analysis on the link of EMIC waves with observed REP to date.« less
  • During enhancement of solar wind dynamic pressure, we observe the periodic emissions of electromagnetic ion cyclotron (EMIC) waves near the nightside geosynchronous orbit (6.6R{sub E}). In the hydrogen and helium bands, the different polarized EMIC waves have different influences on relativistic electrons (>0.8 MeV). The flux of relativistic electrons is relatively stable if there are only the linearly polarized EMIC waves, but their flux decreases if the left-hand polarized (L-mode) EMIC waves are sufficiently amplified (power spectral density (PSD) ≥ 1 nT{sup 2}/Hz). The larger-amplitude L-mode waves can cause more electron losses. In contrast, the R-mode EMIC waves are very weak (PSD < 1 nT{sup 2}/Hz) duringmore » the electron flux dropouts; thus, their influence may be ignored here. During the electron flux dropouts, the relativistic electron precipitation is observed by POES satellite near the foot point (∼850 km) of the wave emission region. The quasi-linear simulation of wave-particle interactions indicates that the L-mode EMIC waves can cause the rapid precipitation loss of relativistic electrons, especially when the initial resonant electrons have a butterfly-like pitch angle distribution.« less
  • The interaction of a relativistic electron beam with a plasma waveguide whose density is modulated by an ion acoustic wave leads to the emission of electromagnetic radiation. The wavelength of the radiation is 2..gamma../sup 2/ times shorter than the ion acoustic wavelength. The emission is accompanied by the amplification of the ion acoustic wave. The maximum amplitudes of the excited waves are found.
  • We show evidence that left-hand polarised electromagnetic ion cyclotron (EMIC) plasma waves can cause the loss of relativistic electrons into the atmosphere. Our unique set of ground and satellite observations shows coincident precipitation of ions with energies of tens of keY and of relativistic electrons into an isolated proton aurora. The coincident precipitation was produced by wave-particle interactions with EMIC waves near the plasmapause. The estimation of pitch angle diffusion coefficients supports that the observed EMIC waves caused coincident precipitation ofboth ions and relativistic electrons. This study clarifies that ions with energies of tens of ke V affect the evolutionmore » of relativistic electrons in the radiation belts via cyclotron resonance with EMIC waves, an effect that was first theoretically predicted in the early 1970's.« less
  • 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 electronsmore » 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 EMIC waves, wave properties, electron minimum resonant energy E min, and electron pitch angle diffusion coefficient D αα of a sample EMIC wave packet are examined along with solar wind plasma and interplanetary magnetic field parameters, geomagnetic activity, and results from the spectral analysis of the BARREL balloon observations to investigate the two types of events. The events occurred in the early main phase of a moderate storm (min. Dst* = -51.0 nT). The EMIC wave event consists of two parts. Finally, unlike the first part, the second part of the EMIC wave event was locally generated and still in its source region. It is found that the REP event is likely associated with the EMIC wave event.« less