This project will investigate the locations of auroral breakup events with respect to the large-scale electric current system connecting the magnetosphere and ionosphere. This framework of large-scale field-aligned currents is created as a result of the interaction between the Earth's magnetic field and the solar wind. The closure of these field-aligned currents through the polar ionosphere is responsible for the auroral oval. Another consequence of the interaction with the solar wind is the extremely stretched magnetic field lines on the nightside of the Earth that form an extended magnetotail. The stretching increases until the energy stored in the magnetic fields is released explosively and the stretching decreases. During this time, the electric current across the magnetotail is disrupted and shunted through the high-latitude ionosphere forming the substorm current wedge. This stretching-release-recovery cycle is called a substorm. The interval during which the stretching increases is called the substorm growth phase; the explosive energy release is an element of the substorm expansion phase (or auroral breakup). The auroral breakup begins with a brightening of an existing arc near midnight close to the lower latitude edge of the auroral oval. This is followed by an initially localized region of bright and rapidly varying auroras that spreads westward and poleward with time. The auroral breakup is thought to be associated with the upward current leg of the substorm current wedge. This study answers important questions about the connection between the large-scale current systems and the disturbed substorm currents associated with the auroral breakup using satellite observations of global field-aligned electric currents and ground-based observations of auroras and geomagnetic field disturbances. An important element of this project is the unique global view enabled by new data products. The project will have significant broader impacts. Summer interns including high school science students and teachers will be involved in the research, receiving training on automatic identification of auroral break-up candidates and other aspects of the research. In the longer term, an increased understanding of explosive space weather disturbances in the vicinity of Earth will improve forecasting capabilities of value to a technology-dependent society.
The primary objective is to determine how auroral breakups relate to the global magnetospheric current systems. The methodology consists of case studies and statistical correlations of auroral breakup timing and location relative to the current systems. This study is only now possible because of the groundbreaking development by the NSF-NASA AMPERE program of global maps of field-aligned currents on a ten-minute cadence utilizing existing engineering magnetometers onboard 66 commercial Iridium communications satellites. These maps will be combined with ground-based maps of geomagnetic field perturbations from the NSF-NASA-ESA supported SuperMAG Program, which is a worldwide collaboration of organizations and national agencies that currently operate more than 300 ground based magnetometers. SuperMAG turns these observations into global maps of magnetic field disturbances and other parameters that measure the level of geomagnetic activity. Finally, auroral breakup images will be obtained from 20 THEMIS ground-based All Sky Imagers (ASIs) distributed across the entire North American polar region (some stations funded by NSF).
