NSF Award
1249270
The Principal Investigator (PI) and his team will investigate the physical relationship between the height profile (or decay index) of the magnetic flux in the corona above a given solar source region and the known 'torus instability' of magnetic flux ropes. They intend to establish that this interaction provides a key link between the magnetic structure of the source region of a coronal mass ejection (CME) and that CME's ultimate eruption velocity. The team expects to determine that this physical influence affects the coronal field's polarity structure at great heights, as well as the association of CME velocity with solar source region size and complexity, the occurrence of precursor CMEs, and the Sun's large-scale coronal density structure. <br/><br/>The PI's parametric numerical investigation will quantify how the height profile and the coronal density structure control the peak rise velocity of unstable magnetic flux ropes, which represent the erupting magnetic flux in CMEs. The steepness of the height profile will be investigated in relation to the structure of the photospheric field while considering bipolar, quadrupolar, and more complex flux distributions, in order to establish quantitative dependencies of the CME velocity on the directly observable source region parameters. These results will be verified by several means, including numerical modeling of selected CME events under realistic thermal and magnetic conditions with events covering a range of moderate to extremely high velocities, and statistical studies of CME velocities that will include, for the first time, the height profiles of the coronal magnetic field (obtained by extrapolations) and newly identified source region parameters. <br/><br/>The peak CME velocity in the solar corona is a key parameter for effective space weather forecasting, since the arrival time and potential impact of CMEs may threaten the nation's astronauts, satellites, and ground-based technologies. This project will build research infrastructure in solar physics by creating a new partnership between Predictive Science, Inc. (PSI) and George Mason University (GMU). These research results will be broadly disseminated in the refereed literature as well as at science workshops and conferences. A catalog of studied CME events, including source region parameters, field extrapolations, and height profiles, will be provided on PSI and GMU web pages for community access, and the PI's simulation output will also be made available upon request. This project will train a graduate student at GMU and support the professional development of a postdoctoral solar physicist at PSI.
