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Ann. Geophys., 22, 549-566, 2004
www.ann-geophys.net/22/549/2004/
© European Geosciences Union 2004
Ionospheric energy input as a function of solar wind parameters: global MHD simulation results
M. Palmroth1, P. Janhunen1, T. I. Pulkkinen1, and H. E. J. Koskinen1,2
1Finnish Meteorological Institute, Geophysical Research Division, Finland
2University of Helsinki, Department of Physical Sciences, Finland
Abstract. We examine the global energetics of the solar wind magnetosphere-ionosphere system
by using the global MHD simulation code GUMICS-4. We show simulation results
for a major magnetospheric storm (6 April 2000) and a moderate substorm
(15 August 2001). The ionospheric dissipation is investigated by determining
the Joule heating and precipitation powers in the simulation during the two
events. The ionospheric dissipation is concentrated largely on the dayside
cusp region during the main phase of the storm period, whereas the nightside
oval dominates the ionospheric dissipation during the substorm event. The
temporal variations of the precipitation power during the two events are
shown to correlate well with the commonly used AE-based proxy of the
precipitation power. The temporal variation of the Joule heating power during
the substorm event is well-correlated with a commonly used AE-based empirical
proxy, whereas during the storm period the simulated Joule heating is
different from the empirical proxy. Finally, we derive a power law formula,
which gives the total ionospheric dissipation from the solar wind density,
velocity and magnetic field z-component and which agrees with the
simulation result with more than 80% correlation.
Key words. Ionosphere (modeling and forecasting) –
Magnetospheric physics (magnetosphere-ionosphere interactions;
storms and substorms)
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