Long-term evolution of magnetospheric current systems during storms

NY Ganushkina*, TI Pulkkinen, MV Kubyshkina, HJ Singer, CT Russell

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

We present a method to model the storm-time magnetospheric magnetic field using representations of the magnetic field arising from the various magnetospheric current systems. We incorporate the effects of magnetotail changes during substorms by introducing an additional localized thin current sheet into the Tsyganenko T89 model. To represent the storm-time ring current the T89 ring current is replaced by a bean-shaped current system, which has a cross section that is close to the observed distribution of trapped particles in the inner magnetosphere and has an eastward flowing inner and westward flowing outer components. In addition to the symmetric ring current, an asymmetric partial ring current is taken into account with closing Region 2 sense field-aligned currents. Magnetopause currents are varied in accordance with solar wind dynamic pressure variations. Three moderate geomagnetic storms when D, reached about - 150 nT and one big storm with D-st about -250 nT are modelled. The model free parameters are specified for each time step separately using observations from GOES 8 and 9. Polar, Interball and Geotail satellites and D-st measurements. The model gives a high time-resolution field representation of the large-scale magnetic field, and a very good reproduction of the D-st index. It is shown that the ring current is most important during intense storms, whereas the near-Earth tail currents contribute more to the D-st index than the ring current during moderate storms.

Original languageEnglish
Pages (from-to)1317-1334
Number of pages18
JournalAnnales Geophysicae
Volume22
Issue number4
Publication statusPublished - 2004
MoE publication typeA1 Journal article-refereed

Keywords

  • magnetospheric physics
  • current systems
  • magnetospheric configuration and dynamics
  • storms and substorms
  • RING CURRENT
  • MAGNETIC-FIELD
  • GEOMAGNETIC STORMS
  • CURRENT SHEET
  • MODEL
  • TAIL
  • MAGNETOPAUSE
  • IONS
  • DST

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