Energetics during the main phase of geomagnetic superstorms

Abstract

The study of energy transfer between the different regions of the solar wind ‐ magnetosphere ‐ ionosphere system is a fundamental issue in Solar‐Terrestrial Physics. In this work we have studied the degradation of the solar wind energy budget through the solar wind ‐ magnetosphere coupling down to the ring current injection and the auroral ionospheric 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, and the total energy flux of high‐latitude precipitating particles collected by the NOAA 6 satellite were used for this study. The solar wind energy budget was determined from the kinetic energy flux of the particles in the interplanetary medium. The energy transfer from the solar wind into the magnetosphere was estimated through a dayside magnetopause ram pressure corrected version of the Perrault and Akasofu ε function. The energy injection into the ring current was estimated under the DPS theorem restriction and introducing the decay parameter τ in the evolution equation as a continuous function of the Dst index. The energy dissipation estimate in the auroral ionosphere via Joule heating in one hemisphere was computed using ionospheric and interplanetary data through a new method. Previous statistical and case studies for substorms have shown that the total energy dissipated as Joule heating is roughly twice that of the ring current injection. Our results show that the energy dissipation via Joule heating in the auroral ionosphere is about half of the ring current energy injection during superstorms.