Open AccessElectron Rolling-pin Distribution Inside Magnetic Hole
Author(s) -
Y. Yu,
H. S. Fu,
Jinbin Cao,
Y. Y. Liu,
Z. Wang
Publication year - 2022
Publication title -
astrophysical journal/the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.3847/1538-4357/ac497a
Subject(s) - physics , pitch angle , electron , magnetic field , computational physics , plasma , atomic physics , nuclear physics , astronomy , quantum mechanics
Magnetic holes (MHs), characterized by depressions in the magnetic field magnitude, are transient magnetic structures ubiquitous in space plasmas. The electron pitch-angle distribution inside the MHs is key to diagnosing the MH properties and has been suggested to mainly exhibit a pancake-type distribution showing pitch angles near 90°. Here, we present the first observation of electron rolling-pin distribution—showing electron pitch angles mainly at 0°, 90°, and 180°—within an electron-scale MH, by using Magnetospheric Multiscale mission high-resolution measurements. With a second-order Taylor expansion method, the magnetic field topology of the MH is reconstructed, and the characteristics of the rolling-pin distribution inside the MH are investigated. We find that the rolling-pin distribution primarily appears near the MH center and at energies ranging from 110 to 1200 eV. We interpret the rolling-pin formation as a consequence of the combination of local-scale electron trapping and global-scale Fermi acceleration. These results can improve current understanding of electron dynamics in the MHs.