Modeling flares in the solar corona coupling SOC models and magnetic reconnection

CHARBONNEAU, P.; MORALES, L. F.

Punta del Este

Simposio; Dynamic Days; 2018

Universidad de la República

p { margin-bottom: 0.25cm; line-height: 120%; }Solarflares are the manifestation of intermittent and impulsive release ofenergy in the corona. The spatial coincidence of flares with magneticstructures at the solar surface leaves no doubt that flares drawtheir energy from the Suns magnetic field. Moreover, their very shortonset time points to magnetic reconnection as the physical mechanismresponsible for extracting that energy. Systematic studies of flaresobserved from the extreme ultraviolet to soft X-rays revealed(Dennis, 1985; Aschwanden, 2011 and references there in) that thefrequency distribution of solar flare energy release follows awell-defined power law, spanning 8 orders of magnitude in flareenergy. In the early ?90s Lu & Hamilton proposed a way toexplain the observed power-laws assuming that solar flares areavalanches of several reconnection events occurring in a solarcoronal loop. We have designed an avalanche model for solar flaresthat uses magnetic field lines as basic dynamical elements. We assumean idealized representation of a coronal loop as a bundle of magneticflux strands wrapping around one another. The model is based on atwo-dimensional cellular automaton with anisotropic connectivity,where linear ensembles of interconnected nodes define the individualstrands collectively making up the coronal loop. The system is drivenby random deformation of the strands, and reconnection is mimickedwhenever the angle subtended by two strands crossing at the samelattice site exceed some preset threshold. We have shown that thissystem produces avalanches of reconnection events characterized byscale-free size distributions that compare very well with existingobservations (Morales & Charbonneau, 2008 and 2009). In this workwe extend the models predicting capabilities of extreme flares bycharacterizing the stress pattern developed by the coronal loop whena the biggest avalanches take place.