COLLECTIVE HEATING AND RADIATION DYNAMICS OF THE AURORAL IONOSPHERIC F2-REGION

A theoretical and experimental study is made of the auroral ionospheric radiation at twice the plasma frequency. The analysis has revealed a close association of this radiation with the collective heating of the ionosphere due to an auroral electron beam. The collective heating source is determined by taking into account the following processes and characteristic properties: collision of thermal electrons with ions, atoms and molecules in the ionosphere; the nonlinear processes that determine the level of plasma turbulence in the region of small gradients of plasma density; the absence or presence of ion-sound turbulence; electron temperature and plasma density variations; and the variation of transverse and longitudinal gradients of the plasma density. In this case, of crucial importance is the last process. A numerical solution of the system of hydrodynamical equations involving the collective heating source has permitted us to predict and describe such a phenomenon in the ionospheric F2-region as the auroral thermal wave, the electron temperature in which reaches approximately 10,000 K, its transverse gradient is approximately 1000 K/km, and the velocity of the ascent is approximately 10 km/s. The calculated rate of decrease of the radiation frequency at 2f(p), caused by the ascent of the auroral thermal wave coincided with the measured one. Observational evidence for such high electron temperatures and temperature gradients in the auroral F2-region is presented.