GEM: Assessing the Relative Importance of Convection and Induced Electric Fields for Particle Transport and Energization in the Inner Magnetosphere

Aerospace Corporation, El Segundo CA

Investigators

Abstract

This project investigates the importance of convection and induction electric fields in the magnetosphere, and their relative roles in the dynamics of the ring current and the plasmasphere. Convection electric fields are generated by the interaction between the solar wind and the Earth's magnetosphere. They are directed approximately from dawn to dusk across the magnetotail and drive plasma sheet ions and electrons from the magnetotail towards the inner magnetosphere. Along the way, convection electric fields play an important role in energizing these plasma sheet particles to high energies and in delivering them to build the storm-time ring current, a torus of high-energy ions and electrons surrounding the Earth. Convection electric fields also play an important role in the location of plasma boundaries, such as the plasmapause. The plasmapause is the steep outer boundary of the plasmasphere, a dense torus formed by the extension of cold ionospheric plasma into the inner magnetosphere. This torus expands outward to occupy the region where the corotation electric field (a radial electric field produced by the movement of magnetic field lines in response to Earth's rotation) dominates over the convection electric field. In disturbed times, the convection electric field strengthens with respect to the essentially unchanging corotation field, diminishing the region where the corotation field dominates. As a result, the outer regions of the plasmasphere are stripped away and convected to the dayside magnetopause where the plasma is lost. However, the electric field is more complicated than the superposition of these two large-scale electric fields. Changing magnetic fields produce electric fields through induction. During magnetic substorms, explosive reconfigurations of the magnetotail fields produce significant "induction" electric fields that introduce smaller scale temporal and spatial variability into the magnetospheric electric field. The primary goal of this proposal is to quantify the relative contributions to inner magnetosphere dynamics of convection and induction electric fields. A more complete understanding of all components of the magnetospheric electric field is important for developing improved space weather forecast models of value to society. This project provides support for the research career of a productive female scientist, and a research experience for an undergraduate intern as well as yearly outreach activities aimed at K-12 students, thus contributing to the future scientific workforce and science literacy. The primary tool for this investigation is a magnetically and electrically self-consistent model of the inner magnetosphere, the Rice Convection Model-Equilibrium (RCM-E). For storm events, measurements of the electric fields in the inner magnetosphere and ionosphere will be compared with the modeled RCM-E electric fields. Initially storms will be simulated with no explicit substorm magnetic field changes. The RCM-E magnetic field, energetic ion fluxes, electron densities, and precipitating electron fluxes will be compared with in-situ measurements by magnetospheric and ionospheric satellites. Finally, results of RCM-E geomagnetic storm simulations that incorporate the effects of substorm reconfigurations of the magnetotail fields will be compared with data to determine the role and importance of induced electric fields.