Abstract
We have studied some eﬀects of electrostatic waves and turbulences on the plasma in the auroral
both E and F regions both experimentally and theoretically.
In the E region, electron heating by Farley-Buneman waves are studied using the EISCAT CP1 data. We ﬁnd that electrons are strongly heated in the magnetic ﬁeld-line direction during highelectric ﬁeld events. The remote site data show that the electron temperature increases almost
the same amount as in the ﬁeld-perpendicular direction, and that electron heating by E region
plasma turbulence is isotropic. We discuss the implementations of our observation for the“plasmon”-electron as well as the wave Joule heating models of the anomalous electron heatingin the E region. [St.-Maurice, 1987]’s model which shows that Farley-Buneman waves have anelectric ﬁeld component both perpendicular and parallel to B and eﬀectively heat electrons canexplain our results. We also suggest that if Te enhancement is rather due to a direct scatteringof electrons by wave ﬁelds not involving electron-neutral collisions, our observation implies thatthese waves should be isotropic.
Because the total energy is conserved, we argue that electrons must partly drift along thebackground electric ﬁeld when the electron temperature is elevated above the background neutraltemperature. We parameterize the eﬀect of the waves by the anomalous (eﬀective) electron
collision frequency νe . We ﬁnd that a rotation of the electron ﬂow direction from a E × B
direction can be up to ∼ 8◦ . Although we could not conﬁrm the rotation with the STARE data,
we point out the possibility of using an optical instrument to test our results. We also discuss
the importance of electron heating on the Magnetosphere-Ionosphere coupling.
By using the Kilpisjärvi IRIS data, we examine the nature of the anomalous (eﬀective) electron
collision frequency. We ﬁnd that including νe in the absorption model leads to overestimation of
the cosmic noise absorption when compared with observation by the Kilpisjärvi IRIS. We ﬁndthat νe has a limited range of application.
In the F region, we have studied incoherent scatter spectra which are a scattering of electromagnetic waves by electrostatic ion acoustic waves and Langmuir waves. We have theoreticallycalculated incoherent scatter spectra for a plasma that consists of electrons with kappa distribution function and ions with Maxwellian neglecting the eﬀects of the magnetic ﬁeld andcollisions.
The ion line spectra have a double-humped shape similar to those from a Maxwellian plasma.
The electron temperatures are underestimated, however, by up to 40% when interpreted assuming Maxwellian distribution. Ion temperatures and electron densities are aﬀected little.
Accordingly, actual electron temperatures might be underestimated when energy input maintaining a high energy tail exists. We have also calculated plasma lines with the kappa distributionfunction. They are enhanced in total strength, and the peak frequencies appear to be slightly
shifted to the transmitter frequency compared to the peak frequencies for a Maxwellian distribution. The damping rate depends on the electron temperature. For lower electron temperatures,
plasma lines for electrons with a κ distribution function are more strongly damped than for aMaxwellian distribution. For higher electron temperatures, however, they have relatively sharp
peaks.