SUPERSONIC DOWNFLOWS IN A SUNSPOT LIGHT BRIDGE

Abstract

We report the discovery of supersonic downflows in a sunspot light bridge\nusing measurements taken with the spectropolarimeter on board the Hinode\nsatellite. The downflows occur in small patches close to regions where the\nvector magnetic field changes orientation rapidly, and are associated with\nanomalous circular polarization profiles. An inversion of the observed Stokes\nspectra reveals velocities of up to 10 km/s, making them the strongest\nphotospheric flows ever measured in light bridges. Some (but not all) of the\ndownflowing patches are cospatial and cotemporal with brightness enhancements\nin chromospheric Ca II H filtergrams. We suggest that these flows are due to\nmagnetic reconnection in the upper photosphere/lower chromosphere, although\nother mechanisms cannot be ruled out.\n