Predictions of reconnected flux, energy and helicity in eruptive solar flares

Abstract

In order to better understand the solar genesis of interplanetary magnetic clouds, I model the magnetic and topological properties of several large eruptive solar flares and relate them to observations. My main hypothesis is that the flux ropes ejected during eruptive solar flares are the result of a sequence of magnetic reconnections. To test this hypothesis, I use the three-dimensional Minimum Current Corona model of flare energy storage (Longcope, 1996) together with pre-flare photospheric magnetic field and flare ribbon observations to predict the basic flare properties: reconnected magnetic flux, free energy, and flux rope helicity. Initially, the MCC model was able to quantify the properties of the flares that occur in active regions with only photospheric shearing motions. Since rotating motions may also play a key role in the flare energetics, I develop a method for including both shearing and rotating motions into the MCC model. I use this modified method to predict the model flare properties and then compare them to the observed quantities. Firstly, for two flares in active regions with fast rotating sunspots, I find that the relative importance of shearing and rotation to those flares depends critically on their location within the parent active region topology. Secondly, for four flares analyzed with the MCC model (three flares described here and one flare described in Longcope et al. (2007)), I find that the modeled flare properties agree with the observed properties within the uncertainties of the methods used. This agreement compels me to believe that the magnetic clouds associated with these four solar flares are formed by low-corona magnetic reconnection during the eruption as modeled by the MCC model, rather than eruption of pre-existing structures in the corona or formation in the upper corona with participation of the global magnetic field. I note that since all four flares occurred in active regions without significant pre-flare flux emergence and/or cancellation, the energy and helicity values I find are due primarily to shearing and rotating motions, which are sufficient to account for the observed flare energy and MC helicity.