Comprehensive radiative MHD simulations of eruptive flares above Collisional Polarity Inversion Lines

In this scheme, we start with a bipolar sunspot configuration and set the spots on collision course by imposing the appropriate velocity field at the footpoints in the subphotospheric boundary. We produce different setups with the same initial spot separation by varying physical parameters such as the collision speed and minimum collision distance.

While all setups lead to the formation of an EUV and X-ray sigmoid structure, only the cases with a close passing of the spots cause flares and mass eruptions. The energy release is in the 1-2 x 1031 erg range, putting the simulated flares into the upper C-class to lower M-class range of GOES X-ray 1-8 ANGS; flux. While the setup with the more distant passing of the spots does not lead to a flare, the corona is nonetheless substantially heated, suggesting noneruptive energy-release mechanisms.