التفاصيل البيبلوغرافية
| العنوان: |
Electron Precipitation Driven by EMIC Waves: Two Types of Energy Dispersion. |
| المؤلفون: |
Grach, Veronika S., Artemyev, Anton V., Demekhov, Andrei G., Zhang, Xiao‐Jia, Bortnik, Jacob, Angelopoulos, Vassilis |
| المصدر: |
Geophysical Research Letters; 5/16/2024, Vol. 51 Issue 9, p1-12, 12p |
| مصطلحات موضوعية: |
DISPERSION (Chemistry), ELECTRONS, ELECTROMAGNETIC interactions, LOW temperature plasmas, ION scattering, ELECTRON scattering, RELATIVISTIC electrons |
| مستخلص: |
Electromagnetic ion cyclotron (EMIC) waves can very rapidly and effectively scatter relativistic electrons into the atmosphere. EMIC‐driven precipitation bursts can be detected by low‐altitude spacecraft, and analysis of the fine structure of such bursts may reveal unique information about the near‐equatorial EMIC source region. In this study, we report, for the first time, observations of EMIC‐driven electron precipitation exhibiting energy, E, dispersion as a function of latitude (and hence L‐shell): two predominant categories exhibit dE/dL > 0 and dE/dL < 0. We interpret precipitation with dE/dL < 0 as due to the typical inward radial gradient of cold plasma density and equatorial magnetic field (∼65% of the statistics). Precipitation with dE/dL > 0 is interpreted as due to an outward radial gradient of the equatorial magnetic field, likely produced by energetic ions freshly injected into the ring current (∼35% of the statistics). The observed energy dispersion of EMIC‐driven electron precipitation was reproduced in simulations. Plain Language Summary: Relativistic electron precipitation from the equatorial magnetosphere deposits significant energy fluxes to the atmosphere below 50 km, and thus naturally alters the atmosphere ionization and contributes to ozone destruction in the mesosphere. This precipitation is, in good part, due to electron resonant interactions with electromagnetic ion cyclotron (EMIC) waves. Although basic theories of this interaction have been well understood, the detailed electron precipitation pattern, which depends on the background plasma and magnetic field conditions in the wave source regions, are not well studied. In this study, we demonstrate a new property of electron precipitation driven by EMIC waves—the dispersion in energy versus latitude as observed by the low‐altitude ELFIN CubeSats. Such dispersion can provide information about the EMIC wave source region and, as it turns out, connect relativistic electron precipitation with one of the most powerful phenomena in the magnetosphere, substorm plasma injections. Key Points: We report two types of energy versus latitude (or L‐shell) dispersion of relativistic electron precipitation observed at ELFINBoth types of dispersion signatures can be attributed to electron scattering by electromagnetic ion cyclotron (EMIC) wavesEnergy dispersion is controlled by the magnetic field radial profile in the EMIC wave source region [ABSTRACT FROM AUTHOR] |
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