Impulsive coronal heating during the interaction of surface magnetic fields in the lower solar atmosphere

Probably the most elongated cartoon in the Archive, this simple representation hides a subtle message. On the left one sees an embedded polarity, above which the magnetic field contains a null, and thus a spine-and-fan geometry, with the observational appearance of a simple loop connecting along the spine to the remote blue polarity.. The dotted field lines can reconnect, producing a "three-legged flare". Alternatively, the right panel shows a more prosaic reconnection induced by emerging flux at a more remote point. The paper is using these examples to explain "impulsive heating events", known more commonly as "flares."