Modeling magnetospheric current response to solar wind dynamic pressure enhancements during magnetic storms: 2. Application to different storm phases

摘要

Two patterns of ground H perturbation as response to pressure enhancements during different phases of storms are found. One is polarity asymmetry under southward IMF B z , e.g., 25 September 1998, 29 May 2003, and 10 January 1997 events; the other is positive H perturbation everywhere under northward IMF B z , e.g., 7 November 2000 event. The polarity asymmetry can be further divided into two categories: dawn-dusk asymmetry with negative H perturbation at dusk extending through noon to late morning (25 September 1998 event) and positive H perturbation elsewhere, and day-night asymmetry with a smaller region of negative H perturbation extending less far toward dusk (29 May 2003 and 10 January 1997 events). The net field-aligned current (FAC) system from the R1, R2, and the partial ring current (PRC) closure FAC, the equatorial portion of the PRC, and Chapman-Ferraro (CF) current are responsible for the polarity asymmetry. The stronger effect of the R1 is primarily responsible for the negative H perturbation at noon and positive at midnight. The PRC strength at the onset of pressure enhancements determines how far the negative H perturbation at noon extends toward dusk and which pattern is most likely. A stronger (weaker) PRC extends negative H perturbation more (less) toward dusk and thus increases the likelihood of dawn-dusk (day-night) asymmetry. Positive H perturbation everywhere results from the dominant contribution of the CF and lack of significant preexisting PRC and R1 and R2.