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Slow mode structure in the nightside magnetosheath related to IMF draping
Author(s) -
Erkaev N. V.,
Farrugia C. J.,
Mezentsev A. V.,
Torbert R. B.,
Biernat H. K.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2013ja019514
Subject(s) - magnetosheath , physics , magnetic field , geophysics , plasma , magnetopause , magnetohydrodynamic drive , equator , magnetohydrodynamics , interplanetary magnetic field , astrophysics , computational physics , latitude , magnetosphere , solar wind , astronomy , quantum mechanics
We apply a semianalytic magnetohydrodynamic approach to describe effects in the nightside magnetosheath related to accelerated magnetosheath flows caused by the draping of interplanetary magnetic field (IMF). Assuming a northward IMF direction, we show the development of slow mode fronts in the far tail (tailward of approximately −60 R m E ). We find that accelerated flows north and south of the equator start to converge toward lower latitudes. The ensuing plasma compression gives rise to slow mode waves in the equatorial region which, further down the tail, evolve into slow mode shocks. These fronts propagating along the magnetic field lines are characterized by sharp increases of plasma density, pressure, and temperature and a decrease in the magnetic field strength. The magnetic pressure exhibits an anticorrelation with the plasma pressure, but the total pressure is fairly constant across the fronts. The field‐aligned plasma velocity component anticorrelates with the plasma density, while the perpendicular velocity component does not have sharp variations at the fronts. For northward IMF, these fronts appear near the equatorial region and then propagate to higher latitudes. This effect is not very sensitive to the particular shape of the magnetopause. Lowering the upstream Alfvén Mach number increases the strength of the slow mode waves, which also develop closer to Earth. We predict that this effect can be observed by space probes skimming the far tail.