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Ann. Geophys., 26, 1415-1430, 2008
www.ann-geophys.net/26/1415/2008/
© European Geosciences Union 2008
Global observations of electromagnetic and particle energy flux for an event during northern winter with southward interplanetary magnetic field
H. Korth1, B. J. Anderson1, J. M. Ruohoniemi1, H. U. Frey2, C. L. Waters3, T. J. Immel2, and D. L. Green3
1The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA
2Space Sciences Laboratory, University of California Berkeley, Berkeley, CA, USA
3School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW, Australia
Abstract. The response of the polar ionosphere–thermosphere (I-T) system to
electromagnetic (EM) energy input is fundamentally different to that
from particle precipitation. To understand the I-T response to
polar energy input one must know the intensities and spatial
distributions of both EM and precipitation energy deposition.
Moreover, since individual events typically display behavior
different from statistical models, it is important to observe the
global system state for specific events. We present an analysis of
an event in Northern Hemisphere winter for sustained southward
interplanetary magnetic field (IMF), 10 January 2002, 10:00–12:00 UT,
for which excellent observations are available from the
constellation of Iridium satellites, the SuperDARN radar network,
and the Far-Ultraviolet (FUV) instrument on the IMAGE satellite.
Using data from these assets we determine the EM and particle
precipitation energy fluxes to the Northern Hemisphere poleward of
60° MLAT and examine their spatial distributions and
intensities. The accuracy of the global estimates are assessed
quantitatively using comparisons with in-situ observations
by DMSP along two orbit planes. While the location of EM power input
evaluated from Iridium and SuperDARN data is in good agreement with
DMSP, the magnitude estimated from DMSP observations is
approximately four times larger. Corrected for this underestimate,
the total EM power input to the Northern Hemisphere is 188 GW.
Comparison of IMAGE FUV-derived distributions of the particle energy
flux with DMSP plasma data indicates that the IMAGE FUV results
similarly locate the precipitation accurately while underestimating
the precipitation input somewhat. The total particle input is
estimated to be 20 GW, nearly a factor of ten lower than the EM
input. We therefore expect the thermosphere response to be
determined primarily by the EM input even under winter conditions,
and accurate assessment of the EM energy input is therefore key to
achieving a comprehensive understanding of the I-T system,
particularly during active times when the energy input increases
markedly and expands well equatorward of nominal auroral latitudes.
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