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Torsional slow-mode oscillations discovered in the magnetic free energy during solar flares View all abstracts by submitter

Markus J Aschwanden   Submitted: 2020-01-27 15:08

We report the discovery of torsional Alfvénic oscillations in solar flares, which modulate the time evolution of the magnetic free energy E_f(t), while the magnetic potential energy E_p(t) is uncorrelated, and the nonpotential energy varies as Enp(t) = E_p + E_f(t). The mean observed time period of the torsional oscillations is Pobs=15.1 ± 3.9 min, the mean field line length is L=135±35 Mm, and the mean phase speed is vphase =315 ± 120 km s-1, which we interpret as torsional Alfvénic waves in flare loops with enhanced electron densities. Most of the torsional oscillations are found to be decay-less, but exhibit a positive or negative trend in the evolution of the free energy, indicating new emerging flux (if positive), magnetic cancellation, or flare energy dissipation (if negative). The time evolution of the free energy has been calculated in this study with the Vertical-Current Approximation (Version 4) Nonlinear Force-Free Field (VCA4-NLFFF) code, which incorporates automatically detected coronal loops in the solution and bypasses the non-forcefreeness of the photospheric boundary condition, in contrast to traditional NLFFF codes.

Authors: Aschwanden,M.J. and Wang,T.J.
Projects: None

Publication Status: ApJ (2020, Jan 27; in press)
Last Modified: 2020-01-29 13:13
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