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Magnetosheath filamentary structures formed by ion acceleration at the quasi‐parallel bow shock
Author(s) -
Omidi N.,
Sibeck D.,
Gutynska O.,
Trattner K. J.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2013ja019587
Subject(s) - magnetosheath , physics , bow shock (aerodynamics) , mach number , solar wind , plasma , bow wave , shock wave , computational physics , shock (circulatory) , magnetic field , magnetopause , astrophysics , mechanics , nuclear physics , medicine , quantum mechanics
Results from 2.5‐D electromagnetic hybrid simulations show the formation of field‐aligned, filamentary plasma structures in the magnetosheath. They begin at the quasi‐parallel bow shock and extend far into the magnetosheath. These structures exhibit anticorrelated, spatial oscillations in plasma density and ion temperature. Closer to the bow shock, magnetic field variations associated with density and temperature oscillations may also be present. Magnetosheath filamentary structures (MFS) form primarily in the quasi‐parallel sheath; however, they may extend to the quasi‐perpendicular magnetosheath. They occur over a wide range of solar wind Alfvénic Mach numbers and interplanetary magnetic field directions. At lower Mach numbers with lower levels of magnetosheath turbulence, MFS remain highly coherent over large distances. At higher Mach numbers, magnetosheath turbulence decreases the level of coherence. Magnetosheath filamentary structures result from localized ion acceleration at the quasi‐parallel bow shock and the injection of energetic ions into the magnetosheath. The localized nature of ion acceleration is tied to the generation of fast magnetosonic waves at and upstream of the quasi‐parallel shock. The increased pressure in flux tubes containing the shock accelerated ions results in the depletion of the thermal plasma in these flux tubes and the enhancement of density in flux tubes void of energetic ions. This results in the observed anticorrelation between ion temperature and plasma density.