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Fast earthward plasma flows observed in the mid/distant tail under quiet conditions: Relation to substorms
Author(s) -
Troshichev O. A.,
Kokubun S.,
Kamide Y.,
Mukai T.,
Yamamoto T.
Publication year - 1999
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 - 10.1029/1999gl900079
Subject(s) - substorm , physics , plasma , plasma sheet , quiet , geophysics , magnetic field , earth's magnetic field , field line , astrophysics , magnetosphere , astronomy , quantum mechanics
Measurements of the magnetic field and low energy plasma by the GEOTAIL spacecraft have been used to study fast earthward plasma flows in the distant (130–200 R E ) and middle (40–80 R E ) tail and their relationship to substorms. Results of the analysis show that high‐speed earthward ion flows are often observed in the mid/distant tail under conditions of low magnetic activity ( AE ∼ 100 nT), when the IMF B Z component is northward or oscillates to about zero. A considerable portion of the fast earthward flows (29% in the distant tail and 53% in the middle tail) seems to be a precursor to substorm expansion onsets on the Earth. These flows occur at closed magnetic field lines. The cause and effect relationship between fast earthward plasma flows in the distant tail and substorm activity suggests that a neutral line can form at distances far beyond 100 R E during quiet conditions.