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The closure of region‐1 field‐aligned current in MHD simulation
Author(s) -
Janhunen P.,
Koskinen H. E. J.
Publication year - 1997
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 - 10.1029/97gl01292
Subject(s) - magnetohydrodynamics , magnetopause , physics , geophysics , field line , ionosphere , magnetic field , daytime , noon , computational physics , mechanics , magnetosphere , atmospheric sciences , quantum mechanics
We have studied the closure path of Region‐1 field‐aligned current system in our global MHD simulation and found some interesting results. After leaving the ionosphere on the eveningside the current deviates from the field‐aligned direction rather early and bends towards the Sun. After passing through the velocity shear region near the magnetopause, which is a generator region, it climbs up along the magnetopause, being more or less field‐aligned. Because of this it again bends sunward. When approaching the noon‐midnight meridian plane ( Y =0 plane in GSM coordinates), however, the current becomes more perpendicular to the magnetic field. It passes through the Y =0 plane at about X =2±1, Z =11±1. On the morningside the closure path is a mirror reflection of that on the evening side. Thus the closure path seems to reside more on the dayside than perhaps usually thought. We give a simple physical explanation for the dayside bending, which is based on the MHD pressure balance equation.