Development of Large-Scale Electric Fields in the Inner Magnetosphere during Substorms

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

This project will focus on temporal variations of electric fields in Earth's magnetosphere that are associated with the onset of a magnetic substorm. It will use data from the THEMIS and Cluster spacecraft as well as the THEMIS ground-based imaging array to precisely determine the time of substorm onset. Data from the THEMIS spacecraft will be used to determine the time difference between substorm auroral onset and the electromagnetic field and Poynting flux responses. These results can then be used to determine the propagation path of energy that lead to the formation of subauroral polarization streams (SAPS). SAPS are a major magnetosphere-ionosphere coupling phenomenon associated with region 2 FACs flowing into the subauroral ionosphere in the premidnight sector. For quantitative understanding of disturbances in the inner magnetosphere during substorms, it is essential to determine the transmission path of electromagnetic energy released in the magnetotail at substorm onset towards the inner magnetosphere, as well as the promptness and spatial distribution of this response. While a number of studies have been conducted for quasi-steady distributions of SAPS electric fields, this project will focus on temporal variations of electric fields associated with substorm onset. The coupling of electromagnetic energy from the magnetosphere to the ionosphere is one of the most important processes that affect space weather. This project will investigate an important component of magnetosphere-ionosphere coupling that is associated with electric fields generated at the onset of a magnetic substorm.