Publication Date:
2014-01-19
Description:
[1] Recent testing of a quantitative model describing the classical (region-1-sense, referred to as the R1 current loop) substorm current wedge (SCW) revealed systematic discrepancies between the observed and predicted amplitudes, which suggested us to include additional region-2-sense currents (R2-loop) earthward of the dipolarized region (SCW2L model). In this paper we discuss alternative circuit geometries of the 3d substorm current system and interpret simultaneous observations of the magnetic field dipolarizations by NOAA Geostationary Operational Environmental Satellite (GOES) and by NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft, to quantitatively investigate the SCW2L model parameters. During two cases of a dipole-like magnetotail configuration, the dipolarization/injection front fortuitously stopped at r ∼ 9 Re for the entire duration of ∼ 30 min-long SCW-related dipolarization within a unique, radially-distributed multi-spacecraft constellation, which allowed us to determine the locations and total currents of both SCW2L loops. In addition, we conducted a survey of the dipolarization amplitudes in events, simultaneously observed at 6.6 Re (GOES) and 11 Re (THEMIS) under a wide range of magnetotail conditions. We infer that the ratio I 2 / I 1 varies in the range 0.2 to 0.6 (median value 0.4) and that the equatorial part of the R2 current loop stays at the distance r 〉 6.6 Re in the case of a dipole-like field geometry ( BZ 0 〉 75 nT at 6.6 Re prior to the onset), but it is located at r 〈 6.6 Re in the case of a stretched magnetic field configuration (with BZ 0 〈 60 nT). Since the ground midlatitude perturbations are sensitive to the combined effect of the R1- and R2-sense current loops with the total current roughly equal to I 1 − I 2 , the ratio I 2 / I 1 becomes an important issue when attempting to monitor the current disruption intensity from ground observations.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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