Experimentally Measured Stability Properties of Arched, Line-Tied Magnetic Flux Ropes

Coronal mass ejections occur when long-lived magnetic flux ropes (MFR) anchored to the solar surface destabilize and erupt away from the Sun. One potential cause for these eruptions is an ideal MHD instability such as the kink or torus instability. These instabilities have long been studied in axisymmetric fusion devices where the instability criteria are given in terms of the edge safety factor and confining magnetic field decay index, respectively. Laboratory experiments have been performed in the Magnetic Reconnection Experiment (MRX), where the stability properties of arched, line-tied MFRs were controlled via the external fields. Previous experiments revealed a class of MFRs that were torus-unstable but kink-stable, which failed to erupt [Alt et al. (2021) ApJ 908 41]. These "failed-tori" went through a process similar to Taylor relaxation where the toroidal current was redistributed before their eruption ultimately failed. In more recent experiments, we have investigated this behavior through additional diagnostics that measure the current distribution at the footpoints. These measurements will confirm whether the current is redistributing along the entire rope or only at the apex, which will give insight into the phenomena responsible for the failed torus events.