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Dipolarization front and current disruption
Author(s) -
Lui A. T. Y.
Publication year - 2016
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 - 10.1002/2016gl070980
Subject(s) - substorm , current sheet , plasma sheet , current (fluid) , physics , instability , plasma , magnetohydrodynamics , front (military) , current density , geophysics , mechanics , computational physics , atomic physics , magnetosphere , meteorology , nuclear physics , quantum mechanics , thermodynamics
The modification of current density on the dawn‐dusk cross section of the magnetotail with the earthward approach of a dipolarization front (DF) is examined through the recently published results of a three‐dimensional (3‐D) particle‐in‐cell (PIC) simulation. It is found that the current density intensifies by ~37% abruptly within ~1.5 ion gyrotime as the DF approaches and shows localized regions with north‐south extrusions. After reaching its peak value, it undergoes a drastic current reduction (DCR) by ~65% within ~2 ion gyrotime. Breakdown of the frozen‐in condition occurs in the neutral sheet region in association with DCR, demonstrating the non‐MHD behavior of the phenomenon. The evolution of current density from this 3‐D PIC simulation bears several similarities to those observed for the current disruption (CD) phenomenon, such as explosive growth and disruption of the current density leading to a breakdown of the frozen‐in condition. The evolution is also similar to those from a previous two‐dimensional (2‐D) PIC simulation specially designed to investigate the nonlinear evolution of the cross‐field current instability for CD. One interpretation of these findings is that CD and substorm triggering can be associated with earthward intrusion of a DF into the near‐Earth plasma sheet as indicated by previous Cluster and Time History of Events and Macroscale Interactions during Substorms observations. An alternative interpretation is that both DF and CD are consequences of a global evolution from an ion‐tearing‐like instability of the magnetotail.