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EP: Fachverband Extraterrestrische Physik

EP 4: Space-Weather-3

EP 4.2: Hauptvortrag

Dienstag, 10. März 2015, 14:30–15:00, G.10.02 (HS 9)

MHD Instabilities and Magnetic Reconnection in Coronal Mass Ejections — •Bernhard Kliem — Universität Potsdam, Institut für Physik und Astronomie

This talk will give an overview of the modeling of solar prominence eruptions and coronal mass ejections (CMEs). Basic considerations of energy storage in the solar corona suggest the existence of an ideal magnetohydrodynamic (MHD) instability or catastrophe—a lateral kink often referred to as torus instability—which can explain the acceleration of the ejecta. Additionally, the helical kink instability may trigger the eruption in some cases. Both instabilities require the existence of a magnetic flux rope at eruption onset, which has recently received more support from observations and numerical simulations. They also lead to the formation of a large-scale vertical current sheet, where magnetic reconnection causes the flare signatures in agreement with the “standard flare model.” An alternative CME model, known as magnetic breakout, suggests that the source region consists of a sheared arcade of magnetic loops and that magnetic reconnection provides the trigger and main driver of the eruption, forming a magnetic flux rope in its course. This model requires a quadrupolar structure of the source region. Slow (so-called tether-cutting) reconnection driven by the photosphere is the dominant process in the pre-eruptive evolution. Future research on CMEs is expected to strongly focus on the pre-eruption source structure and on their interplanetary evolution. Our predictive capabilities are still very limited.