Yihua Zheng, Ph.D. - US grants

This is a three year research project to use data from the new SuperDARN radar at Wallops Island, as well as DMSP and Iridium satellite data to investigate and elicit the origins of what is known as Subauroral Polarization Streams (SAPS). The overarching science question is related to magnetosphere-ionosphere coupling, that is whether the ionosphere passively responds to the situation in the magnetosphere or whether the ionosphere should be considered as more tightly coupled to the magnetosphere so that it influences the whole magnetosphere-ionosphere response to the solar wind drivers. Specific science goals that will be addressed include 1) Quantifying the dawn-dusk asymmetry in the return flow including its variation with IMF clock angle; 2) Quantifying the asymmetry in intensity and latitude of particle precipitation and its relationship to: the return flow intensity, the Birkeland currents, and the IMF clock angle; 3) Determining whether inner magnetospheric convection including ring current physics can account for the observed distributions of flows and Birkeland currents or whether MHD physics without ion drift physics can account for the observed distribution of return flows.

The intellectual merit of this effort lies in significantly advancing our understanding of the storm-time Magnetosphere-Ionosphere system and the mid-latitude electrodynamics that occur during active times. This understanding is needed to advance the fundamental science understanding of geomagnetic storms but also has application to practical areas of importance such as communications and navigation for which strong ionospheric electric fields are of paramount concern. This project also continues an informal partnership between APL and the physics department at Augsburg College that consists in providing summer research opportunities for undergraduate students from Augsburg at APL via the JHU/APL Student Summer Internship program. M-I coupling during magnetic storms is one of the important physical processes that affect the upper atmospheric electrodynamics of the polar region. Thus, the research project will contribute to the larger research goals of the International Polar Year Program at NSF.

The goal of this project is to create a comprehensive model of the inner magnetosphere that includes the interactions of the plasmasphere, the ring current and the radiation belts. The model will be an enhancement of the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model. The coupled model will include the processes by which particles are accelerated, the loss and transport processes and will include a self-consistent description of the electric and magnetic fields.

The project will examine how the inner magnetosphere responds dynamically to the solar wind drivers and how the response to the external drivers is modulated by internal processes. Specific questions that will be addressed are: (1) what is the relationship between EMIC (electromagnetic ion-cyclotron)waves and the loss of ring current ions via particle precipitation, (2) what are the roles of radial transport, wave-particle interactions, and induced electric fields on the variations in relativistic electron fluxes in the radiation belt during different phases of geomagnetic storms, and (3) what determines the sometimes partial, sometimes complete filling of the slot region between the inner and outer radiation belts.

Understanding the interactions between the solar wind drivers, the ring current and the radiation belts has important impacts on our understanding of space weather, including radiation hazards to space-based technological systems and geomagnetic effects on the ground.