Current state-of-the-art for the measurement of non-Maxwellian plasma parameters with the EISCAT UHF Facility

D. Hubert (1) , François Leblanc (2) , P. Gaimard (3)

1 Departement de Recherche Spatiale
2 OBSPM - Observatoire de Paris - Site de Meudon
3 CEPHAG - Centre d'Études des Phénomènes Aléatoires et Géophysiques

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.

Domaines: Océan, Atmosphère; Sciences de la Terre

D. Hubert, François Leblanc, P. Gaimard. Current state-of-the-art for the measurement of non-Maxwellian plasma parameters with the EISCAT UHF Facility. Annales Geophysicae, 1996, 14 (12), pp.1506-1512. ⟨hal-00329064⟩