Do New Solar Active Regions Trigger Flares in Existing Regions?

Thursday, 18 December 2014
Yixing Fu and Brian T Welsch, University of California Berkeley, Berkeley, CA, United States
We study the effect of new emerging solar active regions on the large-scale magnetic environment of existing regions. We first present a theoretical approach to quantify the "interaction energy" between new and pre-existing regions by identifying the part of the magnetic potential field energy that couples the new and old flux systems. We then examine this energy in two well-studied cases of flux emergence, but find that the predicted energetic perturbation is very small compared to energies released in large solar flares. Next, we present an observational study of the influence of the emergence new active regions on flare statistics in pre-existing active regions. As part of an effort to precisely determine the emergence time of active regions in a large sample, we find that emergence in about half of these regions exhibits a two-stage behavior, with an initial gradual phase followed by a more rapid phase. Preliminary results regarding flaring suggest that newly emerging regions trigger a marginally significant increase in the occurrence rate of X- and M-class flares in pre-existing regions.