Comparison of Kinematics of Solar Eruptive Prominences and Spatial Distribution of the Magnetic Decay Index

Abstract

Theoretical studies of electric current instability explaining solar prominence eruptions show that the loss of equilibrium may develop in a case when the surrounding magnetic field decreases sufficiently rapidly with height. The magnetic decay index, a parameter indicating whether the external magnetic field has a configuration that may lead to a certain type of electric current instability, is a useful instrument for predicting the behavior of prominences. In our study, we consider three eruptive prominences. We perform potential-field extrapolation to obtain the spatial distribution of the magnetic decay index in the coronal space identified with the prominences. Analysis of time-dependent height profiles of the prominences revealed that eruptions started at heights close to those, where the computed magnetic decay index exceeded a value equal to 1.5. This indicates that the torus instability is a possible mechanism of the considered eruptive events.