LONG-TERM EVOLUTION OF MAGNETIC AND DYNAMICAL PROPERTIES IN A SUNSPOT LIGHT BRIDGE

Abstract

Sunspot light bridges (LBs)—long bright lanes appearing in umbra—sometimes show dynamical behaviors such as plasma ejections, brightenings, and fast gas flows in the photosphere and lower chromosphere, but we have not understood what causes these dynamics. The Hinode Solar Optical Telescope successfully captured the entire period of the evolution of an LB formed at the southeast of the well-developed sunspot in NOAA Active Region 10953, allowing us to track how magnetic and dynamical properties change with time for 3.5 days. The LB produced chromospheric upward ejections intermittently and recurrently on 2007 April 30, and fewer upward ejections were observed on May 1. We found that G-band intensity features morphologically changed from cellar or patchy on April 30 to filamentary on May 1, although there were small changes in the magnetic flux density and inclination. This suggests that the chromospheric activity is related to the change of morphology in the photosphere. Fast gas flows and a pair of strong enhanced vertical electrical currents were also observed in the photosphere after the filamentary structures were dominant. The end of a large Hα filament (or prominence) was extended very close to the LB on May 1, suggesting that the filamentary structures formed along the LB may be magnetically connected to the large Hα filament and the gas flows may originate far from the LB region, although other mechanisms cannot be ruled out.