Abstract
Abstract. Using EISCAT radar data, we find that electrons are strongly heated in the magnetic field-line direction during high electric field events. The remote site data show that the electron temperature increases in almost the same way in the field-perpendicular direction; electron heating by E region plasma turbulence is isotropic. We discuss the implications of our observation for the "plasmon"-electron as well as the wave Joule heating models of the anomalous electron heating in the E region.Key words. Ionosphere (auroral ionosphere; plasma temperature and density; plasma waves and instabilities)
Highlights
The knowledge and understanding of irregularities in the E region was recently reviewed (Sahr and Fejer, 1996)
It was found that Te starts to increase when the electric field strength |E| exceeds the threshold for excitation of the modified two-stream (or Farley-Buneman) instability (MTSI), Eth
Ogawa et al (1980) has shown that when the electric field is strong, the effective collision frequency of electrons should be enhanced by a factor of 6 to explain the observed aspect angle dependence of phase velocities of E region irregularities
Summary
The knowledge and understanding of irregularities in the E region was recently reviewed (Sahr and Fejer, 1996). Ogawa et al (1980) has shown that when the electric field is strong, the effective collision frequency of electrons should be enhanced by a factor of 6 to explain the observed aspect angle dependence of phase velocities of E region irregularities. If we find anisotropic temperatures, the heating would have to be caused by perpendicular wave fields directly because electron-neutral collisions heat isotropically irrespective of the direction of E0 and δE. Using the E region measurements from the remote EISCAT sites, we have checked the thermal isotropy of the electrons and the ions. The comparisons of the electron and the ion temperatures at 108 km, between Tromsø and Kiruna where the aspect angle is 35◦, are shown in Fig. 3 (left and right), respectively.
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