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The Role of Magnetic Helicity in Solar Activity

Presentation #302.07 in the session From the Photosphere to the Corona, Solar Eruptive Events.

Published onSep 18, 2023
The Role of Magnetic Helicity in Solar Activity

Solar activity ranging from quasi-steady coronal heating to explosive CMEs/flares is widely believed to be due to the transfer of energy from magnetic fields to plasma via the fundamental process of magnetic reconnection. Since magnetic helicity is conserved under reconnection, helicity is a critical constraint on the reconnection dynamics and ensuing energy release. Helicity conservation, therefore, has long been discussed by many authors as the underlying process that shapes much of solar and heliospheric activity. In previous work we proposed the model of helicity condensation showing how helicity conservation coupled with turbulent-like coronal reconnection driven by photospheric convective motions accounts for the generic observed structure of the corona: the laminar loops observed since TRACE and the highly sheared prominences observed for centuries. We present recent calculations elucidating how multiscale photospheric motions affect the helicity condensation process. The important result is that the model is robust, even for complex driving. We consider the implications of helicity condensation for understanding a variety of observations, in particular, the lack of observed twist in prominence fields even though flux cancellation is expected to produce highly twisted fields. We also consider the implications of helicity for understanding failed eruptions. The primary conclusion from our work is that understanding the effects of magnetic helicity conservation is absolutely essential for advancing our understanding of solar activity.

This work was supported by the ISFM program at NASA/GSFC and LWS grants to U Michigan.

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