Presentation #305.06 in the session Explosive Energy Release Processes in the Solar Corona and Earth’s Magnetosphere II.
The physical drivers of solar and stellar flare development during the rise phase remain poorly understood, due, for example, to the observed rapid development of brightenings, which have yet to be reconciled with the longer-duration of the flare rise phase. Variation in flare ribbon geometry, magnetic field structure, and overall flare development complicate the search for a comprehensive theory of flare energetics. A new classification of solar flares using the impulsiveness index provides a framework to better understand the mechanism driving the rapid development of the rise phase in solar and stellar flares. These datasets are used to perform detailed spatial analysis of physical properties in six flares corresponding to a range of impulsiveness values. We determine the parallel and perpendicular stages of flare ribbon motion and corresponding reconnection fluxes and rates and compare these to the chromospheric light curves. We verify that the end of the flare rise phase corresponds to the end of the ribbons’ parallel motion, while perpendicular motion persists afterwards. In addition, we use the relative positions of newly-brightened flare ribbon pixels to determine magnetic shear. Previous work suggests that magnetic shear may be related to rates of particle precipitation. The relationship between magnetic shear and impulsiveness is investigated, providing unique insight into the origin of light curve shapes in stellar flares. These empirical results are combined to guide modeling efforts for reconciling the observed long-duration rise times in white-light stellar flares and short timescale particle injection events.