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Helical Magnetic Cavities: Kinetic Model and Comparison With MMS Observations
Author(s) -
Li JingHuan,
Zhou XuZhi,
Yang Fan,
Artemyev Anton V.,
Zong QiuGang
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2021gl092383
Subject(s) - physics , magnetic field , plasma , dipole model of the earth's magnetic field , computational physics , kinetic energy , classical mechanics , astrophysical plasma , magnetosphere particle motion , spacecraft , mechanics , solar wind , interplanetary magnetic field , quantum mechanics , astronomy
Abstract Magnetic cavities are sudden depressions of magnetic field strength widely observed in the space plasma environments, which are often accompanied by plasma density and pressure enhancement. To describe these cavities, self‐consistent kinetic models have been proposed as equilibrium solutions to the Vlasov‐Maxwell equations. However, observations from the Magnetospheric Multi‐Scale (MMS) constellation have shown the existence of helical magnetic cavities characterized by the presence of azimuthal magnetic field, which could not be reconstructed by the aforementioned models. Here, we take into account another invariant of motion, the canonical axial momentum, to construct the particle distributions and accordingly modify the equilibrium model. The reconstructed magnetic cavity shows excellent agreement with the MMS1 observations not only in the electromagnetic field and plasma moment profiles but also in electron pitch‐angle distributions. With the same set of parameters, the model also predicts signatures of the neighboring MMS3 spacecraft, matching its observations satisfactorily.