University of Oulu

Capannolo, L., Li, W., Ma, Q., Shen, X.‐C., Zhang, X.‐J., Redmon, R. J., et al. (2019). Energetic electron precipitation: Multievent analysis of its spatial extent during EMIC wave activity. Journal of Geophysical Research: Space Physics, 124, 2466– 2483.

Energetic electron precipitation : multievent analysis of its spatial extent during EMIC wave activity

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Author: Capannolo, L.1; Li, W.1; Ma, Q.1,;
Organizations: 1Center for Space Physics, Boston University, Boston, MA, USA
2Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
3Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA, USA
4Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
5National Centers for Environmental Information, NOAA, Boulder, CO, USA
6Department of Physics, Augsburg University, Minneapolis, MN, USA
7Department of Physics and Astronomy, University of Iowa, Iowa City, IA, USA
8Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, USA
9Space Science and Applications Group, Los Alamos National Laboratory, Los Alamos, NM, USA
10Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 10.5 MB)
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Language: English
Published: American Geophysical Union, 2019
Publish Date: 2019-09-09


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 magnetospheric waves observed simultaneously with EMIC waves, namely, plasmaspheric hiss and magnetosonic waves, and find that the electron precipitation at MeV energies was predominantly caused by EMIC‐driven pitch angle scattering. Interestingly, each precipitation event observed by a LEO satellite extended over a limited L shell region (ΔL ~ 0.3 on average), suggesting that the pitch angle scattering caused by EMIC waves occurs only when favorable conditions are met, likely in a localized region. Furthermore, we take advantage of the LEO constellation to explore the occurrence of precipitation at different L shells and magnetic local time sectors, simultaneously with EMIC wave observations near the equator (detected by Van Allen Probes) or at the ground (measured by magnetometers). Our analysis shows that although EMIC waves drove precipitation only in a narrow ΔL, electron precipitation was triggered at various locations as identified by POES/MetOp over a rather broad region (up to ~4.4 hr MLT and ~1.4 L shells) with similar patterns between satellites.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 124
Issue: 4
Pages: 2466 - 2483
DOI: 10.1029/2018JA026291
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This research is supported by NSF grant AGS‐1723588, AFOSR grant FA9550‐15‐1‐0158, and the Alfred P. Sloan Research Fellowship FG‐2018‐10936. Work at Augsburg University was supported by NSF grant AGS‐1651263. The work at the University of Iowa was performed under the support of JHU/APL contract 921647 under NASA Prime contract NAS5‐01072.
Copyright information: ©2019. American Geophysical Union. All Rights Reserved.