Abstract
Abstract The role of ideal-MHD instabilities in a prominence eruption is explored through 2D and 3D kinematic analysis of an event observed with the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory between 22:06 UT on 2013 February 26 and 04:06 UT on 2013 February 27. A series of 3D radial slits are used to extract height–time profiles ranging from the midpoint of the prominence leading edge to the southeastern footpoint. These height–time profiles are fit with a kinematic model combining linear and nonlinear rise phases, returning the nonlinear onset time (t nl) as a free parameter. A range (1.5–4.0) of temporal power indices (i.e., β in the nonlinear term ) are considered to prevent prescribing any particular form of nonlinear kinematics. The decay index experienced by the leading edge is explored using a radial profile of the transverse magnetic field from a PFSS extrapolation above the prominence region. Critical decay indices are extracted for each slit at their own specific values of height at the nonlinear phase onset (h(t nl)) and filtered to focus on instances resulting from kinematic fits with (restricting β to 1.9–3.9). Based on this measure of the critical decay index along the prominence structure, we find strong evidence that the torus instability is the mechanism driving this prominence eruption. Defining any single decay index as being “critical” is not that critical because there is no single canonical or critical value of decay index through which all eruptions must succeed.
Highlights
Based on this measure of the critical decay directly related to the magnetic field gradient, as will be discussed further later
The TI is best thought of as a loss of equilibrium between a radially outward force and a radially inward force. This force balance was originally described by Shafranov (1966), who considered it as a toroidal Lorentz force combined with the net pressure gradient of a curved current channel balanced by the transverse component of an external poloidal magnetic field, Bex, generated by a Lorentz force
The work of Olmedo & Zhang (2010) outlines the properties of the partial torus instability (PTI), which considers how changing the ratio of the arc length of the partial torus above the photosphere to the circumference of a circular torus of equal radius can change the critical value of the decay index
Summary
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