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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 30, issue 6
Ann. Geophys., 30, 927–928, 2012
https://doi.org/10.5194/angeo-30-927-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 30, 927–928, 2012
https://doi.org/10.5194/angeo-30-927-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 04 Jun 2012

Regular paper | 04 Jun 2012

On the relaxation of magnetospheric convection when Bz turns northward

M. C. Kelley M. C. Kelley
  • School of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA

Abstract. The solar wind inputs considerable energy into the upper atmosphere, particularly when the interplanetary magnetic field (IMF) is southward. According to Poynting's theorem (Kelley, 2009), this energy becomes stored as magnetic fields and then is dissipated by Joule heat and by energizing the plasmasheet plasma. If the IMF turns suddenly northward, very little energy is transferred into the system while Joule dissipation continues. In this process, the polar cap potential (PCP) decreases. Experimentally, it was shown many years ago that the energy stored in the magnetosphere begins to decay with a time constant of two hours. Here we use Poynting's theorem to calculate this time constant and find a result that is consistent with the data.

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