Location of high-altitude cusp during steady solar wind conditions

M Palmroth*, Harri Laakso, TI Pulkkinen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

We have investigated the high-altitude cusp location and its dependence on the interplanetary magnetic field (IMF) B-z, solar wind B-y, and solar wind dynamic pressure during steady solar wind conditions. We have adopted strict event selection criteria, where we have studied only events during stationary IMF B-z, when the cusp latitude is supposed to be stationary. Prior to this study, the statistical studies have shown a great deal of scatter between the cusp latitude and the IMF B-z; however, with the strict event selection criteria, we have been able to reduce the scatter. The strongest source of scatter comes from large and largely fluctuating IMF B-y. When the events are selected during small IMF B-y, the scattering between the cusp latitude and the IMF B-z is reduced. When IMF is southward, also the fluctuation of IMF B-y has strong influence on the cusp latitude, whereas for northward IMF, the IMF B-y fluctuation has less influence on the cusp latitude. For larger southward IMF the cusp appears further equatorward than with smaller southward IMF. When the scatter is reduced by introducing the IMF B-y control, the larger northward IMF brings the cusp to lower latitudes than the smaller northward IMF, i.e., the maximum cusp latitude is obtained for small positive IMF B-z. For increasing solar wind E-y the cusp moves equatorward. Furthermore, with increasing solar wind dynamic pressure, the cusp appears at lower latitudes. This behavior depends on the orientation of the IMF B-z, with southward IMF the cusp moves faster equatorward than with northward IMF.

Original languageEnglish
Pages (from-to)21109-21122
Number of pages14
JournalJournal of Geophysical Research
Volume106
Issue numberA10
Publication statusPublished - 1 Oct 2001
MoE publication typeA1 Journal article-refereed

Keywords

  • INTERPLANETARY MAGNETIC-FIELD
  • LOW-LATITUDE RECONNECTION
  • DIPOLE TILT ANGLE
  • POLAR CUSP
  • DAYSIDE IONOSPHERE
  • PARTICLE-PRECIPITATION
  • MAGNETOSPHERIC CUSPS
  • BOUNDARY-LAYER
  • LOCAL TIME
  • HF RADAR

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