This research aims to explore variations of electron pitch-angle distribution (PAD) during spacecraft cross reconnecting current sheets (RCSs) with magnetic islands. The results can benchmark the sampled characteristic features with realistic PADs derived from in-situ observations.
Particle motion is simulated in 2.5D Harris-type RCSs using particle-in-cell (PIC) method considering the plasma feedback to electromagnetic fields.
We evaluate particle energy gains and PADs in different locations and under the different directions of passing the current sheet by a virtual spacecraft.
The RCS parameters are comparable to heliosphere and solar wind conditions.
The energy gains and the PADs of particles would change depending on the specific topology of magnetic fields. Besides, the observed PADs also depend on the crossing paths of the spacecraft.
When the guiding field is weak, the bi-directional electron beams (strahls) are mainly present inside the islands and located closely above/below the X-nullpoints in the inflow regions. The magnetic field relaxation near X-nullpoint converts the PADs towards 90 degrees.
As the guiding field becomes larger, the regions with bi-directional strahls are compressed towards small areas in the exhausts of RCSs.
Mono-directional strahls are quasi-parallel to the magnetic field lines near the X-nullpoint due to the dominant Fermi-type magnetic curvature drift acceleration. Meanwhile, the high-energy electrons confined inside magnetic islands create PADs about 90 degrees.
Our results link the electron PADs to local magnetic structures and directions of spacecraft crossings. This can help explain a variety of the PAD features reported in the recent observations in the solar wind and the Earth’s magnetosphere.
Authors: V. Zharkova and Q. Xia
Publication Status: Astronomu and Astrophysics, in press
Last Modified: 2021-02-17 10:09