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Abstract:

We present a statistical analysis of ion distributions in magnetic reconnection jets using data from the Magnetospheric Multiscale spacecraft. Compared with the quiet plasma in which the jet propagates, we often find anisotropic and non-Maxwellian ion distributions in the plasma jets. We observe magnetic field fluctuations associated with unstable ion distributions, but the wave amplitudes are not large enough to scatter ions during the observed travel time of the jet. We estimate that the phase-space diffusion due to chaotic and quasiadiabatic ion motion in the current sheet is sufficiently fast to be the primary process leading to isotropization.

Abstract:

AbstractPlasma jets are ubiquitous in the Earth's magnetotail. Plasma jet fronts (JFs) are a seat of particle acceleration and energy conversion. JFs are commonly associated with dipolarization fronts (DFs), which are often characterized by solitary sharp large‐amplitude increases in the northward component of the magnetic field Bz. However, MHD and kinetic instabilities can develop at JFs and disturb the front structure which questions on the occurrence of solitary DFs at the JFs. We investigate the structure of JFs using 5 years (2017–2021) of the Magnetospheric Multiscale observations in the central plasma sheet (CPS) in the Earth's magnetotail. We compiled a database of 2394 CPS jets. We find that 42% of the JFs are associated with large‐amplitude changes in Bz. However, solitary DFs constitute a quarter of these large‐amplitude events, while the rest are associated with more complex structures.