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Ann. Geophys., 23, 2051-2068, 2005
www.ann-geophys.net/23/2051/2005/
© European Geosciences Union 2005
Assessment of ionospheric Joule heating by GUMICS-4 MHD simulation, AMIE, and satellite-based statistics: towards a synthesis
M. Palmroth1, P. Janhunen1, T. I. Pulkkinen1, A. Aksnes2, G. Lu3, N. Østgaard2, J. Watermann4, G. D. Reeves5, and G. A. Germany6
1Finnish Meteorological Institute, Space Research Division, Helsinki, Finland
2University of Bergen, Department of Physics and Technology, Bergen, Norway
3High Latitude Observatory, National Center for Atmospheric Research, Boulder, CO, USA
4Danish Meteorological Institute, Atmosphere Space Research Division, Farum, Denmark
5Los Alamos National Laboratory, Los Alamos, NM, USA
6Center for Space Plasma and Aeronomy Research, University of Alabama in Huntsville, Huntsville, AL, USA
Abstract. We investigate the Northern Hemisphere Joule heating from several observational and computational sources with the purpose
of calibrating a previously identified functional dependence between solar wind parameters and ionospheric total energy consumption computed
from a global magnetohydrodynamic (MHD) simulation (Grand Unified Magnetosphere Ionosphere Coupling Simulation, GUMICS-4). In this paper,
the calibration focuses on determining the amount and temporal characteristics of Northern Hemisphere Joule heating. Joule heating during
a substorm is estimated from global observations, including electric fields provided by Super Dual Auroral Network (SuperDARN) and Pedersen
conductances given by the ultraviolet (UV) and X-ray imagers on board the Polar satellite. Furthermore, Joule heating is assessed from several
activity index proxies, large statistical surveys, assimilative data methods (AMIE), and the global MHD simulation GUMICS-4. We show that the
temporal and spatial variation of the Joule heating computed from the GUMICS-4 simulation is consistent with observational and statistical methods.
However, the different observational methods do not give a consistent estimate for the magnitude of the global Joule heating. We suggest that
multiplying the GUMICS-4 total Joule heating by a factor of 10 approximates the observed Joule heating reasonably well. The lesser amount of
Joule heating in GUMICS-4 is essentially caused by weaker Region 2 currents and polar cap potentials. We also show by theoretical arguments
that multiplying independent measurements of averaged electric fields and Pedersen conductances yields an overestimation of Joule heating.
Keywords. Ionosphere (Auroral ionosphere; Modeling and
forecasting; Electric fields and currents)
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