Articles | Volume 33, issue 8
Regular paper
07 Aug 2015
Regular paper |  | 07 Aug 2015

Statistical analysis of storm-time near-Earth current systems

M. W. Liemohn, R. M. Katus, and R. Ilie

Abstract. Currents from the Hot Electron and Ion Drift Integrator (HEIDI) inner magnetospheric model results for all of the 90 intense storms (disturbance storm-time (Dst) minimum < −100 nT) from solar cycle 23 (1996–2005) are calculated, presented, and analyzed. We have categorized these currents into the various systems that exist in near-Earth space, specifically the eastward and westward symmetric ring current, the partial ring current, the banana current, and the tail current. The current results from each run set are combined by a normalized superposed epoch analysis technique that scales the timeline of each phase of each storm before summing the results. It is found that there is a systematic ordering to the current systems, with the asymmetric current systems peaking during storm main phase (tail current rising first, then the banana current, followed by the partial ring current) and the symmetric current systems peaking during the early recovery phase (westward and eastward symmetric ring current having simultaneous maxima). The median and mean peak amplitudes for the current systems ranged from 1 to 3 MA, depending on the setup configuration used in HEIDI, except for the eastward symmetric ring current, for which the mean never exceeded 0.3 MA for any HEIDI setup. The self-consistent electric field description in HEIDI yielded larger tail and banana currents than the Volland–Stern electric field, while the partial and symmetric ring currents had similar peak values between the two applied electric field models.

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Short summary
The different electric current systems flowing in the near-Earth nightside magnetosphere each have a unique contribution to the magnetic and electric field distortion of geospace. This study quantifies the intensity and timing of five current systems as calculated from 90 storm events using an inner magnetospheric drift physics model. There is a systematic progression through the various current systems, leading to implications for nonlinear feedback on the geospace system.