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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 11
Ann. Geophys., 15, 1399–1411, 1997
https://doi.org/10.1007/s00585-997-1399-x
© European Geosciences Union 1997
Ann. Geophys., 15, 1399–1411, 1997
https://doi.org/10.1007/s00585-997-1399-x
© European Geosciences Union 1997

  30 Nov 1997

30 Nov 1997

A statistical study of ion frictional heating observed by EISCAT

J. A. Davies1, M. Lester1, and I. W. McCrea2 J. A. Davies et al.
  • 1Radio and Space Plasma Physics Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
  • 2EISCAT Group, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK

Abstract. Results of a statistical survey of F-region ion frictional heating are presented, a survey which is based on over 4000 h of common programme observations taken by the European incoherent scatter (EISCAT) UHF radar facility. The criterion adopted in this study for the identification of ion frictional heating was that defined by McCrea et al., requiring an enhancement in the F-region field-parallel ion temperature exceeding 100 K over two consecutive integration periods, which was itself based on a selection criterion for frictional heating derived for the study of high-latitude F-region ion temperature observations from the Atmospheric Explorer-C satellite. In the present study, the diurnal distribution of ion frictional heating observed by EISCAT is established and, furthermore, its dependence on geomagnetic activity and the orientation of the interplanetary magnetic field (IMF) is investigated; results are interpreted with reference to corresponding distributions of enhanced ion velocity, again derived from the extended set of EISCAT UHF common programme observations. The radar, due to its location relative to the large-scale convection pattern, observes ion frictional heating principally during the night, although preferentially during the post-midnight hours where there is reduced coupling between the ion and neutral populations. There is an increased preponderance of frictional heating during intervals of high geomagnetic activity and for a southward z component of the IMF and, moreover, evidence of asymmetries introduced by the y component of the IMF.

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