Parametric dependence of electric field variability in the Sondrestrom database: A linear relation with Kp

摘要

Motivated by the question of the auroral region contribution to thermospheric heating, the database from the Sondrestrom incoherent scatter radar is used to study the variability of the high-latitude vector electric field. The ability of various geophysical parameters to describe the variability is evaluated, using a minimum variance criterion, and it is found that the standard deviation scales linearly with Kp. It is also found that magnetic latitude and magnetic local time are important descriptors and that the specific dependance largely agrees with variability measurements made by the DE 2 satellite, even though the latter measurements probe a much higher frequency range. A number of other parameters are found to be less important as descriptors, including the IMF clock angle and the season. Thermospheric global circulation models currently incorporate an auroral zone heat source in the form of Joule heating associated with the mean electric field , where the mean is taken over temporal and spatial scales below the models resolution. However, comparison of the modeling outputs with MSIS suggests that the auroral zone heat source is underestimated. Because it is the mean of the squared electric field that determines Joule heating and not the square of the mean, the electric field variability has been put forward as the missing source. Our results indicate that this heat source may be parameterized by Kp, which carries the further implication that the variability is associated with a global-scale phenomenon.