Left panel: The magnetic field structure (Baumann et al. 2012b) above solar active region AR10191, which produced a Class C flare on November 16, 2006. The magnetic field topology is dominated by a 3D null point, associated with a small dark region with opposite (“parasitic”) polarity, inside a larger patch of white polarity. The right-hand side panel shows (in yellow-to-purple colours) the chromospheric locations where high-energy, nonthermal electrons hit the chromosphere (red “floor” in the figure) according to a particle-in-cell model (Baumann et al. 2012a).