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We investigate which scalar quantity or quantities can best predict the lossof equilibrium and subsequent eruption of magnetic flux ropes in the solarcorona. Our models are initialized with a potential magnetic arcade, which isthen evolved by means of two effects on the lower boundary: firstly a gradualshearing of the arcade, modelling differential rotation on the solar surface,and secondly supergranular diffusion. These result in flux cancellation at thepolarity inversion line and the formation of a twisted flux rope. We use threemodel setups: full magnetohydrodynamics (MHD) in cartesian coordinates, and themagnetofrictional model in both cartesian and polar coordinates. The flux ropesare translationally-invariant, allowing for very fast computational times andthus a comprehensive parameter study, comprising hundreds of simulations andthousands of eruptions. Similar flux rope behavior is observed using eithermagnetofriction or MHD, and there are several scalar criteria that could beused as proxies for eruptivity. The most consistent predictor of eruptions ineither model is the squared current in the axial direction of the rope,normalised by the relative helicity, although a variation on the previouslyproposed 'eruptivity index' is also found to perform well in both themagnetofrictional and MHD simulations.

Eruptivity Criteria for Solar Coronal Flux Ropes in Magnetohydrodynamic and Magnetofrictional Models