Laboratory for Nuclear Science, MIT
Friday, February 10, 2017
Abstract: Coronal loops on the surface of the sun appear to be magnetic flux ropes containing plasma. They can undergo fast dynamic events such as solar flares and coronal mass ejections that can release large amounts of radiation or energetic particles, potentially enough to seriously affect the earth and major components of modern life, such as satellites, GPS, and electrical power lines. Ideas developed for toroidal laboratory plasmas used in magnetically confined fusion are shown to also describe coronal loops, despite the enormous differences in scales and parameters. The first consistent steady states in ideal MHD (magnetohydrodyamics) are derived. The solar gravity, although quite small, is found to play an important role in the steady state, where it can set a maximum stable size for the loop that is stable against radial expansion. The strong effects arise in part because gravity provides a small nonaxisymmetry in an otherwise toroidally axisymmetric plasma, an effect also observed in laboratory plasmas from different sources. Comparison to solar observations shows that a simple coronal loop model describes the steady states of at least one type of commonly observed coronal loop.
Bio: Dr. Linda Sugiyama earned a degree in applied mathematics at MIT. Since then, she has worked on many subjects in plasma physics and magnetic fusion as a research scientist at MIT. Recent work has concentrated on the nonlinear simulation of instabilities in fusion plasmas with fluid-like models and the development of large scale computational models for simulation. She proposed the nonlinear two-fluid model (electron and ion fluids) to generalize single-fluid MHD for high temperature plasmas, which has became the basis for the extended MHD model now widely used in fusion.