Dartmouth Events

Physics and Astronomy/Thayer Plasma Seminar - Joel Dahlin, NASA-GSFC

Title: "Magnetic Self-Organization and Catastrophic Energy Release in the Solar Corona"

Tuesday, November 5, 2019
4:00pm – 5:00pm
Wilder 202
Intended Audience(s): Public
Categories: Lectures & Seminars

Abstract: Explosive solar activity in the form of coronal mass ejections and eruptive flares is generally agreed to be powered by the explosive ejection of highly stressed coronal magnetic fields. Magnetic reconnection has long been understood to be the primary driver for the explosive energy release. However, recent studies suggest that reconnection may also play an important role in both the formation and destabilization of the pre-eruptive field. We report on new 3D MHD numerical simulations that definitively demonstrate three distinct roles of reconnection in the evolution of an eruptive flare. The initial configuration consists of a current-free (potential) magnetic field with a coronal null point, and energy and helicity are injected into the corona via small-scale surface flows. A reconnection-mediated inverse helicity cascade concentrates highly sheared mgnetic fields above photospheric reversals in the radial magnetic field. The resulting localized magnetic pressure deforms the coronal null point into a current sheet that eventually reconnects, destabilizing quasi-statc balance by removing restraining tension. The configuration expands outward slowly, stretching the magnetic field lines to form a flare current sheet. Onset of fast reconnection at this sheet expels the accumulated shear and drives rapid energy release. We discuss interesting implications of these results for reconnection-driven particle acceleration in the solar corona.

For more information, contact:
Tressena Manning

Events are free and open to the public unless otherwise noted.