ENERGETICS DURING THE MAIN PHASE OF GEOMAGNETIC SUPERSTORMS

The study of energy transfer between the different regions of the sola r wind - magnetosphere - ionosphere system is a fundamental issue in S olar-Terrestrial Physics. In this work we have studied the degradation of the solar wind energy budget through the solar wind - magnetospher e coupling down to the ring current injection and the auroral ionosphe ric dissipation during the main phase of magnetic superstorms (Dst < - 240 nT). The interplanetary magnetic field, density, temperature, and solar wind velocity measurements collected by the ISEE 3 satellite, an d the total energy flux of high-latitude precipitating particles colle cted by the NOAA 6 satellite were used for this study. The solar wind energy budget was determined from the kinetic energy flux of the parti cles in the interplanetary medium. The energy transfer from the solar wind into the magnetosphere was estimated through a dayside magnetopau se ram pressure corrected version of the Perrault and Akasofu epsilon function. The energy injection into the ring current was estimated und er the DPS theorem restriction and introducing the decay parameter tau in the evolution equation as a continuous function of the Dst index. The energy dissipation estimate in the auroral ionosphere via Joule he ating in one hemisphere was computed using ionospheric and interplanet ary data through a new method. Previous statistical and case studies f or substorms have shown that the total energy dissipated as Joule heat ing is roughly twice that of the ring current injection. Our results s how that the energy dissipation via Joule heating in the auroral ionos phere is about half of the ring current energy injection during supers torms.