| Global modelling of geotail and ring current dynamics underdisturbed conditions |
| V. Kalegaev |
| Skobeltsyn Institute of Nuclear Physics,Moscow State University, Moscow 119992 Russia |
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The storm-time dynamics of magnetospheric current systems during several magnetic storms of different intensities was investigated in terms of the paraboloid model of the Earth's magnetosphere. The moderate magnetic storm on June 25-26, 1998 and severe magnetic storm on October 21-23, 1999 were studied in details. The relative contributions from the ring, magnetotail and magnetopause currents to the $Dst$-index were calculated to analyse the storm-time current systems dynamics. The calculations were based on the "official" methodics of Dst calculations. The quiet time level and quiet time contributions from different current systems were subtracted from the horizontal component of magnetospheric magnetic field calculated for each modeled storm event. Since the currents in the magnetosphere induce currents in the diamagnetic Earth, the contribution of those induced currents to measured perturbation field were also considered. It was obtained that ring current contribution is comparable with tail currents one for moderate storm but it dominates during severe magnetic storm. The ring current/tail current relative contribution to the Dst rises with the growth of the magnetic storm intensity. |
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