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Electron Bernstein waves driven by electron crescents near the electron diffusion region
W Y Li1,2,3, D B Graham4, Yu V Khotyaintsev5
1State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, 100190, Beijing, China. wyli@spaceweather.ac.cn.
Nature Communications
|January 11, 2020
Summary
Large-amplitude electron Bernstein waves (EBWs) observed near Earth's magnetopause drive electron diffusion. These plasma waves, generated by agyrotropic electron distributions, play a key role in magnetic reconnection processes.
Area of Science:
- Space Physics
- Plasma Physics
- Astrophysics
Background:
- Earth's magnetopause is a dynamic boundary where solar wind and Earth's magnetic field interact.
- Magnetic reconnection is a fundamental process in plasma physics, releasing stored energy.
- Electron diffusion regions (EDRs) are critical sites within magnetic reconnection where electron kinetics become dominant.
Purpose of the Study:
- Investigate plasma wave phenomena within an electron diffusion region (EDR) at Earth's magnetopause.
- Identify the source and characteristics of observed plasma waves.
- Determine the role of these waves in electron dynamics and energy dissipation during magnetic reconnection.
Main Methods:
- Analysis of in-situ data from the Magnetospheric Multiscale (MMS) spacecraft.
- Characterization of electron velocity distributions and plasma wave properties.
- Correlation of wave generation with specific plasma conditions, such as agyrotropic distributions.
Main Results:
- Detection of large-amplitude electron Bernstein waves (EBWs) at the boundary of the Hall current reversal within the EDR.
- Identification of crescent-shaped, agyrotropic electron velocity distributions as the driver for EBWs.
- Observation of EBW propagation towards the central EDR and their significant amplitude.
Conclusions:
- Electron Bernstein waves are generated by finite gyroradius effects of outflow electrons in asymmetric magnetic reconnection.
- The observed EBWs are energetic enough to thermalize and diffuse electrons near the EDR.
- EBWs contribute significantly to cross-field electron diffusion at the Hall current reversal boundary, impacting the EDR structure.
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