NSF Award
0548915
This project seeks to understand the dynamics of the Earth's ring current during magnetic storms and to understand its effects on the inner magnetospheric (IM) magnetic field structure. While it is well known that the formation of a ring current leads to large magnetic field depressions in the inner magnetosphere, there is not yet a sufficient comprehensive understanding of global variations in IM magnetic field structure during magnetic storms. Such an understanding is critically needed because the IM magnetic field affects IM particle transport, energization, and loss. The approach toward this objective is to apply magnetically and electrostatically self-consistent kinetic ring current simulations for storm events and to compare the simulation results with in-situ particle measurements from satellite instruments such as the CAMMICE and MFE instruments on and energetic neutral atom(ENA) images ENA images from the IMAGE spacecraft.<br/><br/>The project will specifically address (a) the spatial and temporal variation of the ring current and its magnetic signature for different geomagnetic storms, (b) the asymmetry of the ring current and how well the ASY-H index characterizes such asymmetries, (c) the actual contribution of the ring current to the Dst magnetic index, (d) the amount that induced electric fields mitigate the energization of ring current particles during the main phase and (if at all) prolong the recovery phase of a magnetic storm, and (e) the effects of self-consistent electrostatic fields, by taking account of magnetospheric plasma pressure and ionospheric conductances (including effects of precipitating electrons) on particle transport and loss. As part of this research, an assessment of how well self-consistent simulation-based kinetic models of the ring current can account for plasma pressure and current density distributions (inferred from ion-flux measurements) and measured magnetic and electric intensities will be made. In addition to simulating storm events, numerical experiments will be made to elucidate the physical processes. The simulations and simulation/data comparisons of the ring-current magnetic field will help guide community-wide efforts toward developing more realistic models of the inner magnetospheric magnetic field that are critically needed for research and space weather applications.
