Observations of Supersonic Downflows in a Sunspot Light Bridge as Revealed by Hinode

TL;DR

This study reports the detection of localized supersonic downflows in a sunspot light bridge using Hinode spectropolarimetric data, revealing magnetic inhomogeneities and chromospheric brightness enhancements.

Contribution

It provides new high-resolution observations linking supersonic downflows to magnetic discontinuities and chromospheric activity in sunspot light bridges.

Findings

Supersonic downflows occur in localized patches near magnetic azimuth changes.

Downflows are sometimes co-spatial with chromospheric brightness enhancements.

Magnetic inhomogeneities at small scales may facilitate field line reconnection.

Abstract

Recent high resolution spectropolarimetric observations from Hinode detected the presence of supersonic downflows in a sunspot light bridge (Louis et al. 2009). These downflows occurred in localized patches, close to regions where the field azimuth changed by a large value. This apparent discontinuity in the field azimuth was seen along a thin ridge running along the western edge of the light bridge. Some, but not all, of these downflowing patches were co-spatial with chromospheric brightness enhancements seen in Ca II H filtergrams. The presence of magnetic inhomogeneities at scales of 0.3 arcsec could facilitate the reconnection of field lines in the lower chromosphere whose signatures might be the supersonic downflows and the brightness enhancements that have been observed.