Empirical modeling of a CIR-driven magnetic storm

• Published in: Journal of Geophysical Research: Space Physics 2010-07, Vol.115 (A7), p.n/a
• Main Authors: Sitnov, M. I., Tsyganenko, N. A., Ukhorskiy, A. Y., Anderson, B. J., Korth, H., Lui, A. T. Y., Brandt, P. C.
• Format: Article
• Language: English
• Subjects: Alignment; Atmospheric sciences; Coronal mass ejection; corotating interaction regions; Dynamic pressure; Electric currents; Empirical analysis; empirical geomagnetic field modeling; Empirical models; Equatorial currents; Evolution; Geomagnetic field; Geomagnetism; Geophysics; Inflow; Iridium; Iridium network; Low altitude; Magnetic fields; Magnetic storms; Magnetism; Magnetopause; Magnetosphere; Magnetospheres; Mathematics; Ring currents; Solar corona; Solar wind; Storms; Time series; Wind effects
• ISSN: 0148-0227; 2169-9380; 2156-2202; 2169-9402
• DOI: 10.1029/2009JA015169

The empirical analysis of structure and evolution of the geomagnetic field and underlying electric currents during the 8–11 March 2008 magnetospheric storm, driven by a corotating interaction region, is presented. It is based on the high‐resolution geomagnetic field model TS07D (http://geomag_field.jhuapl.edu/model/) and the low‐altitude mapping of field‐aligned currents obtained using Iridium satellites. Compared to storms, driven by coronal mass ejections, the equatorial currents are found to be overall more dawn‐dusk symmetric. Only in the early main phase a moderate hook‐like westward current flowing from the Region‐2 inflow area on the dawn side to the dusk/afternoon magnetopause is detected, along with an eastward current near the pre‐noon magnetopause. New tail‐type currents are found to dominate the storm‐time magnetosphere in early main and recovery phases at the moments of strong peaks of the solar wind dynamic pressure. Similar effects, found in CME‐driven storms, coincide in time with the plasma sheet density bursts. A clear distinction between the periods dominated by the partial ring current and the tail‐type currents seen in the model agrees with the Iridium data that indicate a significant reduction and contraction of the field‐aligned current pattern in the latter case. Overall small magnitudes of the total field‐aligned currents, with rather transient enhancements, appear to be the most distinctive feature of CIR‐driven storms. Comparison between the model and observations made by five THEMIS probes shows good agreement on storm timescales. Moreover, every deviation arising during a substorm reveals characteristic signatures of the tail current sheet thinning and dipolarization.