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Ann. Geophys., 23, 3313-3322, 2005
www.ann-geophys.net/23/3313/2005/
© European Geosciences Union 2005
A self-consistent derivation of ion drag and Joule heating for atmospheric dynamics in the thermosphere
X. Zhu, E. R. Talaat, J. B. H. Baker, and J.-H. Yee
The Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099, USA
Abstract. The thermosphere is subject to additional electric and magnetic forces, not
important in the middle and lower atmosphere, due to its partially ionized
atmosphere. The effects of charged particles on the neutral atmospheric
dynamics are often parameterized by ion drag in the
momentum equations and Joule heating in the energy equation. Presented
in this paper are a set of more accurate parameterizations for the ion drag
and Joule heating for the neutral atmosphere that are functions of the difference between
bulk ion velocity and neutral wind. The
parameterized expressions also depend on the magnetic field, the Pedersen
and Hall conductivities, and the ratio of the ion cyclotron frequency to the
ion-neutral collision frequency. The formal relationship between the
electromagnetic energy, atmospheric kinetic energy, and Joule heating is
illustrated through the conversion terms between these three types of
energy. It is shown that there will always be an accompanying conversion of
kinetic energy into Joule heating when electromagnetic energy is generated
through the dynamo mechanism of the atmospheric neutral wind. Likewise,
electromagnetic energy cannot be fully converted into kinetic energy without
producing Joule heating in the thermosphere.
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