Direct Observation of Sub-Relativistic Electron Precipitation Driven by EMIC Waves
Abstract
Wave-particle interactions can lead to particle loss through precipitation into the Earth's upper atmosphere. Radiation belt and ring current dynamics can be significantly affected by such mechanisms. Energetic electron precipitation can enhance ionization levels in the Earth's ionosphere and therefore alter the chemical composition. Electromagnetic ion cyclotron (EMIC) waves, with frequencies below the proton gyrofrequency, are known to efficiently scatter 10s - 100s keV protons and ~MeV electrons at low to intermediate pitch angles, while the minimum energy of electrons that can be efficiently scattered in the loss cone is currently under debate.
We show evidence of sub-relativistic electron precipitation driven by EMIC waves using a collection of spacecraft from the Heliophysics System Observatory in magnetic conjunction with Low Earth Orbit (LEO) satellites. Specifically, magnetospheric in-situ wave observations are provided by Van Allen Probes and GOES together with ground-based magnetometers, while precipitating particle data at LEO are obtained from POES and the FIREBIRD-II CubeSats. We provide direct evidence that the observed EMIC waves lead to electron precipitation from ~1 MeV down to ~250 keV, as observed by the differential energy channel detectors onboard FIREBIRD-II units. In conjunction, proton precipitation was observed by POES in a nearby region, supporting EMIC-driven precipitation. We follow up the observations with quasi-linear calculation of the diffusion coefficients due to the observed waves, and show how the sub-relativistic electron precipitation was primarily driven by EMIC waves.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSM23C3220C
- Keywords:
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- 2764 Plasma sheet;
- MAGNETOSPHERIC PHYSICS;
- 2774 Radiation belts;
- MAGNETOSPHERIC PHYSICS;
- 7859 Transport processes;
- SPACE PLASMA PHYSICS;
- 7867 Wave/particle interactions;
- SPACE PLASMA PHYSICS