Studying the conditions for magnetic reconnection in solar flares with and without precursor flares

Forecasting of solar flares remains a challenge due to the limited understanding of the underlying physical processes of these events, in particular magnetic reconnection. Studies have indicated that changes to the photospheric magnetic fields associated with magnetic reconnection – particularly in relation to the field helicity – occur during solar flare events. This study utilized data from the Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager (HMI) and SpaceWeather HMI Active Region Patches (SHARPs) to analyze full vector-field component data of the photospheric magnetic field during solar flare events within a near decade long HMI dataset. Analysis of the data was used to identify and compare the trends of differing flare classes for varying time intervals leading up to an event, as well as the trends of flares that occur with and without a precursor flare, in order to discern signatures of the physical mechanisms involved. The data suggests that active regions that produce flares with precursors are continuing to evolve and appreciably more complex than those that produce a flare without a precursor. Additionally, precursor flares were found to enhance the shear across an active region, helping set up the conditions necessary for a larger solar flare to occur. Ultimately none of the SHARP parameters showed a distinct signature of magnetic reconnection. •Differences in active region magnetic parameters between flares with and without a precursor are greatest for X-class flares.•The effect of precursors in adjusting the magnetic conditions of an active region is most significant within a 6-hour period.•ARs with X-class flares with no precursor have reached max growth; ARs with X-class flares with a precursor are still growing.•Precursors enhance the shear over an AR, helping set up conditions for magnetic reconnection necessary for a larger flare.