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We present a new simulation setup using the MURaM radiativeMagnetohydrodynamic (MHD) code that allows to study the formation ofcollisional polarity inversion lines (cPILs) in the photosphere and the coronalresponse including flares. In this scheme we start with a bipolar sunspotconfiguration and set the spots on collision course by imposing the appropriatevelocity field at the footpoints in the subphotospheric boundary. We producedifferent setups with the same initial spot separation by varying physicalparameters such as the collision speed and minimum collision distance. Whileall setups lead to the formation of an EUV and X-ray sigmoid structure, onlythe cases with a close passing of the spots cause flares and mass eruptions.The energy release is in the $1-2 \times 10^{31}$ erg range, putting thesimulated flares into the upper C-class to lower M-class range of GOES X-ray1-8 A flux. While the setup with the more distant passing of the spots does notlead to a flare, the corona is nonetheless substantially heated, suggestingnon-eruptive energy release mechanisms. We focus our discussion on twoparticular setups that differ in spot coherence and resulting cPIL lengthpersistence. We find different timings in the transition from a shearedmagnetic arcade (SMA) to magnetic flux rope (MFR); the setup with a largelength but shorter duration cPIL produces a MFR during the eruption, while theMFR is pre-existing in the setup with a large length and longer duration cPIL.While both result in flares of comparable strength and the eruption of a CME,the setup with pre-existing MFR (and embedded filament) leads to an MFReruption with a larger mass content.

Comprehensive radiative MHD simulations of eruptive flares above collisional polarity inversion lines