Auroral energy input from energetic electrons and Joule heating at Chatanika

Abstract

With the incoherent scatter radar at Chatanika, Alaska, a wide variety of measurements can be made related to the ionosphere, magnetosphere, and neutral atmosphere. A significant parameter is the amount of energy transferred from the magnetosphere into the ionosphere and neutral atmosphere during periods of auroral activity. In this report we examine a procedure whereby the incident energy flux of auroral electrons is ascertained from radar measurements. As part of the process we compare radar-determined fluxes with those ascertained from simultaneous photometric observations at 4278 •. The fluxes obtained by both techniques had similar magnitudes and time variations. If we assume that the largest uncertainty in the radar/photometer comparison is the effective recombination coefficient, then that coefficient can also be deduced. We find a value 3 X 10 -? cm3/s at about 105 km, which is in good agreement with other recent determinations during active auroral conditions. We then combine this technique with one to ascertain the Joule heating to determine the energy input from the magnetosphere to the ionosphere in a region localized above the radar on March 22, 1973, in the midnight sector. The energy input is continuous at a significant level, i.e., greater than the 3 ergs/cm • s that could be delivered by the sun, were it overhead. Moreover, at times, each of these inputs became as great as 30 ergs/cm • s.

Density Perturbations in the Upper Atmosphere Caused by the Dissipation of Solar Wind Energy

“…Many of his views were subsequently confirmed by direct measurements, especially by those obtained by the Chatanika incoherent backscatter facility (e.g. Wickwar 1975;Wickwar et al 1975;Brekke 1976;Banks 1977Banks , 1980. Because of the importance of this heating mechanism, its physics is summarized in Fig.…”

A study of geomagnetic storms

“…Note that it is again assumed that an increase of j is due mainly to an enhancement of the conductivity and thus of the electron density: see also Wickwar, Baron &Sears (1975).…”

Hemispherical Joule heating and the AE indices

“…However, this important quantity has been very difficult to monitor continuously over the entire polar region. Direct measurements of ionospheric electric fields and conductivities, with rocket-borne instrumentation [e.g., Evans et al, 1977;Theile et al, 1981] or with the incoherent scatter Chatanika radar [e.g., Wickwar et al, 1975;Vickrey et al, 1982], can only provide Joule heating rates integrated over a small area. Therefore a geomagnetic index such as AE has been used (and will probably be used in the future, too) as a firstapproximation measure of the global Joule heating rates [e.g., Perreault and Akasofu, 1978], since it is the only quantity readily available for most time periods of interest.…”