Timing of changes in the solar wind energy input in relation to ionospheric response

T. I. Pulkkinen, M. Palmroth, P. Janhunen, H. E.J. Koskinen, D. J. McComas, C. W. Smith

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We investigate four consecutive substorms using observations and global MHD simulation code GUMICS-4. The solar wind energy input is estimated by the epsilon parameter and evaluated from the simulation by direct integration of the energy transfer through the magnetopause. The ionospheric dissipation is estimated using the AE index and also evaluated by computing the Joule heating from both hemispheres in the simulation. Our results show that there is a clear and repeatable time delay between changes in the solar wind parameters and the energy input through the magnetopause. In the simulation, the Joule heating is quite directly driven by the energy input through the magnetopause, without any significant delays. The AE index shows two distinct responses: when the energy input through the magnetopause increases, the AE index responds with a delay; this can be interpreted as the growth phase. When the energy input decreases, the AE decreases simultaneously, without any significant delay. This indicates that after the onset, the energy input to the ionosphere is directly controlled by the energy input through the magnetopause. The results suggest that the recovery phase timing is determined by the solar wind parameters (with a delay associated with the magnetopause processes), while the onset timing is associated with internal magnetotail and/or magnetosphere-ionosphere coupling processes.

Original languageEnglish (US)
Article numberA00I09
JournalJournal of Geophysical Research: Space Physics
Issue number12
StatePublished - 2010
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Space and Planetary Science


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