Spiraling magnetic field lines within Mercury's magnetosphere. "Flux Transfer Events" are those originating from the Magnetopause, while Plasmoids are those originating from within the Magnetotail. They allow solar wind particles direct access to its surface, where they collide with the surface and kick up material, which replenishes Mercury's atmosphere. Mercury's distance from the sun can only account for 30% of these events, some undetermined property is responsible for the rest.
Mercury/Flux Transfer Events - Magnetic tornadoes originating in Mercury's magnetopause and terminating at its surface. These are magnetic field lines that coil and penetrate the magnetosphere, allowing a path for particles from the sun to follow to strike Mercury's surface. These "storms" are much more powerful than those at Earth. Mercury's atmosphere may be replenished from the Sun via these storms.
Mercury/Plasmoids - Magnetic Tornadoes that originate from within Mercury's Magnetotail.