Different magnetospheric modes: solar wind driving and coupling efficiency

Research output: Contribution to journalArticleScientificpeer-review


Research units

  • Finnish Meteorological Institute
  • University of California at Los Angeles
  • University of Saskatchewan
  • University of Bergen
  • NOAA
  • Los Alamos Natl Lab, Los Alamos National Laboratory, United States Department of Energy (DOE)


This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC) intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential), particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to) the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY). Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading-unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations) during geomagnetically active conditions.


Original languageEnglish
Pages (from-to)4281-4291
Number of pages11
JournalAnnales Geophysicae
Issue number11
Publication statusPublished - 2009
MoE publication typeA1 Journal article-refereed

    Research areas

  • Magnetospheric physics, Magnetosphere-ionosphere interactions, Solar wind-magnetosphere interactions, Storms and substorms, HIGH-LATITUDE CONVECTION, SUBSTORM, FIELD, MAGNETOTAIL, IONOSPHERE, SIGNATURE, DYNAMICS, CANOPUS, DRIVEN, REGION

ID: 2574471