The Role of the Ring Current in Inner Magnetosphere Cross-Energy Coupling

Abstract:

The ring current plays an important role in the processes of energy transport through the inner magnetosphere into the subauroral ionosphere, and as a source of particle precipitation into the atmospheric regions located equatorward of the auroral zone. A large fraction of the solar wind energy transferred into the magnetosphere during geomagnetic storms is consumed by the buildup of the storm-time ring current. As the ring current decays during the storm recovery phase, its energy is released into the atmosphere, ionosphere, and plasmasphere causing effects such as subauroral electron temperature enhancements, detached proton arcs, and energetic neutral atom (ENA) fluxes. Ring current pressure gradients drive the Region-2 field-aligned currents that further modify the overall convection pattern and can have significant feedback on ring current dynamics. In addition, the storm-time ring current development affects radiation belt dynamics in various ways: a) it depresses the background magnetic field on the nightside, which affects the subsequent transport of radiation belt electrons, b) its electron component represents a highly variable, asymmetric, low-energy seed population of the radiation belts, and c) the unstable ring current ion and electron populations generate electromagnetic ion cyclotron (EMIC), magnetosonic, and chorus waves (with different intensities and spatial distributions) that scatter radiation belt particles. Results from recent ring current modeling studies using self-consistently calculated electric and magnetic fields that illustrate these coupling processes are presented and discussed.