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Distant tail plasma jetting and B z properties at slow‐mode shocks: A model of reconnection during northward IMFs
Author(s) -
Ho C. M.,
Tsurutani B. T.
Publication year - 1995
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 - 10.1029/95gl02794
Subject(s) - substorm , physics , magnetic reconnection , shock (circulatory) , plasma , flow (mathematics) , geophysics , astrophysics , line (geometry) , magnetic field , mechanics , magnetosphere , nuclear physics , geometry , medicine , quantum mechanics , mathematics
Previous distant geotail studies find a difference in the locations where the plasma flow reverses direction (x ≈ −120 R e ) and where the magnetic field B z reverses (x ≈ −200 R e ). These results raise some questions about the standard Petchek reconnection model and its applicability. In this study, we use 66 slow‐mode shock events to study the flow properties both earthward and tailward of the x‐type neutral line. The location of the neutral line relative to the spacecraft is determined by: a) use of the measured slow‐mode shock orientation, and b) the magnetic B z polarity. We find that plasmasheet flow speeds downstream of slow shocks are similar, using either of the above two methods. On average, for events tailward of the neutral line, the tailward flow speed is statistically higher than for earthward cases by ∼100–150 km/s. This is consistent with magnetic reconnection where jetting plasma flows of 50–75 km/s are superposed on top of a more‐or‐less continuous high speed tailward convection flow of ∼ 600 km/s. By examining the relationship between these slow shock events in the distant tail and upstream IMF orientations, we also find that a significant amount (40%) of slow shock events occurs during northward IMFs. Thus, we propose a distant tail model of reconnection during northward IMF periods. Using this model and the standard substorm reconnection model (southward IMF cases), we believe we can explain all observations in this paper.