An Observationally Constrained Model of a Flux Rope that Formed in the Solar Corona
2018
Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the coronae of stars. Understanding the plasma
processes involved in CME initiation has applications for space weather forecasting and laboratory plasma experiments.
James et al. used extreme-ultraviolet (EUV) observations to conclude that a magnetic flux rope formed in the solar
corona above NOAA Active Region 11504 before it erupted on 2012 June 14 (SOL2012-06-14). In this work, we use
data from the Solar Dynamics Observatory (SDO) to model the coronal magnetic field of the active region one hour
prior to eruption using a nonlinear force-free field extrapolation, and find a flux rope reaching a maximum height of
150 Mm above the photosphere. Estimations of the average twist of the strongly asymmetric extrapolated flux rope are
between 1.35 and 1.88 turns, depending on the choice of axis, although the erupting structure was not observed to kink.
The decay index near the apex of the axis of the extrapolated flux rope is comparable to typical critical values required
for the onset of the torus instability, so we suggest that the torus instability drove the eruption.
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