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Ann. Geophys., 14, 1506-1512, 1996
www.ann-geophys.net/14/1506/1996/
© European Geosciences Union 1996
Current state-of-the-art for the measurement of non-Maxwellian plasma parameters with the EISCAT UHF Facility
D. Hubert1, F. Leblanc1, and P. Gaimard2
1Departement de Recherche Spatiale, CNRS-URA 264, Observatoire de Paris, 92195 Meudon Cedex, France
2Cephag, Domaine Universitaire, BP 46, 38402 St.-Martin d'Hères, France
Abstract. New results on the information that can be
extracted from simulated non-Maxwellian incoherent radar spectra are presented.
The cases of a pure ionosphere and of a composite ionosphere typical of a given
altitude of the auroral F region are considered. In the case of a pure
ionosphere of NO+ or O+ ions it has been shown that the
electron temperature and the electron density can be derived from a Maxwellian
analysis of radar spectra measured at aspect angles of 0° or 21° respectively;
the ion temperature and ion temperature anisotropy can be derived from a non-
constraining model such as the 1D Raman fitting of a complementary measurement
made at an aspect angle larger than 0° for the NO+ ions, or at an
aspect angle larger than 21° for the O+ ions. Moreover with such
measurements at large aspect angles, the shape of the velocity ion distribution
functions can simultaneously be inferred. The case of a composite ionosphere of
atomic O+ and molecular NO+ ions is a difficult challenge
which requires simultaneously a complementary measurement of the electron
temperature to provide the ion composition and the electron density from the
incoherent radar spectra at a specific aspect angle of 21°; hence, a model
dependent routine is necessary to derive the ion temperatures and ion
temperature anisotropies. In the case where the electron temperature is not
given, a routine which depends on ion distribution models is required first: the
better the ion distribution models are, the more accurately derived the plasma
parameters will be. In both cases of a composite ionosphere, the 1D Raman
fitting can be used to keep a check on the validity of the results provided by
the ion distribution model dependent routine.
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