Yokoh

This Yohkoh picture of a cusp, from the Nuggets Page and Astronomical Picture of the Day Page is associated with open coronal magnetic field lines which allow the solar wind to blow. Though exactly how it works is unknown, flares and other types of solar activity can open normally “closed” coronal magnetic fields (closed refers to both ends of a field line intersecting the solar surface, and neither end straggling out into the cosmos.