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Fast Ion Isotropization by Current Sheet Scattering in Magnetic Reconnection Jets
Louis Richard1, Yuri V Khotyaintsev2, Daniel B Graham2
1Swedish Institute of Space Physics, Uppsala 751 21, Sweden and Department of Physics and Astronomy, Space and Plasma Physics, Uppsala University, Uppsala 751 20, Sweden.
Physical Review Letters
|September 29, 2023
Summary
Anisotropic ion distributions in magnetic reconnection jets are common. Chaotic ion motion in the current sheet likely causes this isotropization, not magnetic field fluctuations.
Area of Science:
- Space Physics
- Plasma Physics
- Astrophysics
Background:
- Magnetic reconnection is a fundamental process in plasma physics, crucial for energy transfer in space plasmas.
- Magnetospheric Multiscale (MMS) mission provides in-situ measurements of plasma phenomena in Earth's magnetosphere.
Purpose of the Study:
- To statistically analyze ion distributions within magnetic reconnection jets.
- To investigate the causes of observed ion anisotropies and non-Maxwellian features.
Main Methods:
- Statistical analysis of ion distribution functions using MMS spacecraft data.
- Correlation analysis between ion distributions and magnetic field fluctuations.
- Modeling of ion motion and diffusion in reconnection current sheets.
Main Results:
- Ion jets associated with magnetic reconnection frequently exhibit anisotropic and non-Maxwellian distributions.
- Magnetic field fluctuations are present but generally insufficient to isotropize ions within the observed jet travel time.
- Phase-space diffusion from chaotic and quasi-adiabatic ion motion in the current sheet is a likely dominant mechanism for isotropization.
Conclusions:
- Ion dynamics in magnetic reconnection jets are complex, deviating significantly from quiescent plasma.
- Current sheet ion dynamics, rather than wave-particle interactions during jet propagation, are key to understanding ion isotropization.
- Further research into phase-space diffusion is warranted to fully explain ion energization and distribution evolution.
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