Premium
RCM‐E and AMIE studies of the Harang reversal formation during a steady magnetospheric convection event
Author(s) -
Yang Jian,
Toffoletto Frank,
Lu Gang,
Wiltberger Michael
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020207
Subject(s) - ionosphere , geophysics , substorm , electric field , convection , magnetosphere , earth's magnetic field , geology , atmospheric sciences , asymmetry , magnetic field , physics , mechanics , quantum mechanics
This paper presents the results of a modeling study on the formation of the Harang reversal (HR) during a steady magnetospheric convection event. The Harang reversal is identified as the boundary of the northward and southward electric field in the nightside auroral zone using the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure. We simulate the event with the Rice Convection Model‐Equilibrium (RCM‐E) by adjusting its boundary conditions to approximately match Time History of Events and Macroscale Interactions during Substorms (THEMIS) and GOES observations in the nightside magnetosphere. Our results show that the HR is collocated with an upward region 1 field‐aligned current, where converging ionospheric currents cause a southward/northward electric field on the poleward/equatorward side of the HR. Our results also indicate that the electric field reversal is slightly poleward of the ionospheric east–west current reversal and is to the northeast of the ground magnetic reversal, which is consistent with previous observations. We also test the sensitivity of the HR formation to a variety of parameters in the RCM‐E simulations. We find that (1) the reduction of the flux tube entropy parameter PV 5/3 near the midnight sector plays a major role in the formation of the HR; (2) a run carried out assuming uniform conductance produced the same major features as the run with more realistic precipitation‐enhanced conductance; and (3) the detailed pattern of the polar cap potential distribution plays a minor role, but its dawn‐dusk asymmetry significantly controls the location of the HR with respect to midnight. The RCM‐E simulations also predict PV 5/3 and flow distributions associated with the magnetospheric source of the HR in the plasma sheet, which can be further tested against observations.