Effects of dipole tilt angle on geomagnetic activity

M. Nowada, J. H. Shue, C. T. Russell

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The relationship between the orientation of the interplanetary magnetic field (IMF), represented by the clock angle which is the angle defined by IMF-By and -Bz components, and the AL and AU indices is examined at various dipole tilt angles for the period of 1978-1988. We use the IMF data obtained from the IMP 8 satellite, AL and AU indices with corrected seasonal variations, and the dipole tilt angle, which is the dipole magnetic latitude of the subsolar point calculated as a function of the day of year and universal time. For both positive (dipole tilted to the Sun) and negative dipole tilt angles, the values of | AL | and AU decrease as the IMF clock angle moves away from 180{ring operator}, becoming more northward. The indices also tend to become smaller for larger dipole tilt angle, either toward or away from the Sun. This dependence on dipole tilt angle enhances the semiannual variation of geomagnetic activity.

Original languageEnglish
Pages (from-to)1254-1259
Number of pages6
JournalPlanetary and Space Science
Issue number11
StatePublished - Sep 2009


  • Dipole tilt
  • Geomagnetic activity
  • Interplanetary magnetic field
  • Magnetic reconnection
  • Semiannual variation


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