Open AccessQuantitative modeling of the magnetic field configuration associated with the theta aurora
Author(s) -
Naehr S. M.,
Toffoletto F. R.
Publication year - 2004
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2003ja010191
Subject(s) - physics , interplanetary magnetic field , geophysics , field line , magnetopause , magnetosphere , magnetohydrodynamics , plasma sheet , convection , magnetic field , polar , twist , current sheet , astrophysics , solar wind , computational physics , geometry , mechanics , astronomy , mathematics , quantum mechanics
The relationships among the interplanetary magnetic field (IMF), the global magnetospheric configuration, and the polar cap configuration known as the theta aurora are explored, using simulations generated by the Rice Field Model and the BATSRUS global MHD model. Two phenomena that have been linked to theta auroras are examined: a “convection gap,” or region of zero magnetic normal component on the magnetopause, associated with antiparallel merging during periods of steady, predominantly northward IMF, and a reconfiguration of the tail lobe and plasma sheet twist following abrupt IMF rotations. It is found that (1) the convection gap does not produce configurations consistent with the theta aurora, (2) large‐angle rotations of the IMF produce partial bifurcations of the open‐closed boundary and tail lobes and field‐aligned current patterns that are consistent with the theta aurora, (3) reconfiguration of the plasma sheet during IMF rotations, rather than relocation of the merging line, is critical to the development of theta aurora‐like configurations, (4) a sufficient magnetotail length, longer than produced in MHD simulations but consistent with the Rice Field Model, can account for the observed duration and velocity of theta auroras created by a single IMF rotation, (5) multiple IMF rotations do not significantly affect the duration of the theta configuration but may lead to multiple transpolar arcs.