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Fine structure of field‐aligned current sheets deduced from spacecraft and ground‐based observations: Initial FREJA results
Author(s) -
Lühr H.,
Warnecke J.,
Zanetti L. J.,
Lindqvist P. A.,
Hughes T. J.
Publication year - 1994
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 - 10.1029/94gl01278
Subject(s) - electrojet , spacecraft , magnetic field , current (fluid) , geophysics , physics , field (mathematics) , electric field , current sheet , event (particle physics) , field line , orbit (dynamics) , ionosphere , current density , computational physics , geodesy , geology , astrophysics , earth's magnetic field , aerospace engineering , astronomy , magnetohydrodynamics , mathematics , quantum mechanics , pure mathematics , engineering , thermodynamics
Due to its special orbit—over large segments tangential to the auroral oval and at altitudes around 1600 km—FREJA provides measurements from a sparsely sampled region. Here we will introduce initial results from the magnetic field experiment. For one event occurring about an hour after midnight we investigate the fine structure of the field‐aligned currents associated with a westward electrojet. From simultaneous ground‐based observations we deduce the orientation and the spatial and temporal variations of the electrojet. Space‐borne magnetic field measurements provide estimates of the field‐aligned current density. We deduce a lower limit of 1.75 km for the thickness of field‐aligned current filaments. The comparison between electric and magnetic field recordings on FREJA suggests a poor correlation of these quantities for this event.