Electric Conductivities, Currents And Energy Dissipation In The Polar Ionosphere

Abstract

During the International Magnetospheric Study (IMS), magnetic records from the six IMS meridian chain stations were obtained on March 17, 18 and 19, 1978. The data set is one of the most comprehensive ever obtained. Furthermore, several advanced computer codes calculating ionospheric current distributions based on the ground magnetic data were recently introduced. Combining the data set and the computer code developed by Kamide et al. (1981), it is attempted to re-examine the longstanding uncertainties in the current distributions and the energy dissipation rates in the polar ionosphere during substorms. For this purpose, a conductivity model which can reflect substorm conditions on an instantaneous basis was obtained based on the empirical relations of the north-south component ((DELTA)H) of the magnetic disturbance field observed at College, with the Pedersen and Hall conductivities deduced from Chatanika radar observations. In addition, the relationship of the particle energy injection rate, estimated from the radar, to (DELTA)H is also established. Based on the conductivity model thus obtained and the computer code, the ionospheric current distributions of 5-minute time resolution are obtained. Several interesting features in the current distributions during each phase of substorm are discussed. Furthermore, a new ionospheric current model during a substorm is schematically suggested. The IMF effects on the current patterns are also discussed. For several events, the roles of the ionospheric Pedersen and Hall currents are examined separately. By constructing the hourly distribution map of the Joule heat production rate, the particle energy injection rate and their sum over the entire polar region, it is possible to estimate the global Joule heat production rate, the global particle energy injection rate and the sum of the two quantities. It is found that the three global quantities are related almost linearly to the AE and AL indices.