Average height-integrated Joule heating rates and magnetic deflection vectors due to field-aligned currents during sunspot minimum

Abstract

Height-integrated Joule heating has been calculated from simultaneous observations of field-aligned currents and precipitating electrons made by the Defense Meterorological Satellite Program (DMSP) satellite F7. The DMSP/F7 satellite provided nearly continuous data from January 1984 to October 1987. In this paper we use data from January 1984 to December 1985, a period of nearly uniform, low solar EUV flux near the minimum of the sunspot cycle. By assuming that the majority of the observed field-aligned currents connect through the ionosphere via local Pedersen currents, we have calculated the local Joule heating rates. By combining Joule heating observations from multiple orbits, a survey of Joule heating vs magnetic latitude, magnetic local time, magnetic activity level and season has been compiled. In addition, the average magnetic deflection vector has been compiled. Our survey of the distribution of Joule heating has finer resolution than previous surveys, and is comparable with previous case studies. We have found evidence that the source of the field-aligned current into/out of the dayside cusp is on open field lines and that the source of the field-aligned current into/out of the auroral zones is on closed field lines.