Impact of Magnetic and Flow Fields on Penumbrae and Light Bridges of Three Leading Sunspots in an Active Region

Abstract

This study investigates penumbrae and light bridges based on photospheric and chromospheric flow fields and photospheric magnetic fields in active region NOAA 13096. The improved High-resolution Fast Imager (HiFI+) and the GREGOR Infrared Spectrograph (GRIS) acquired high-resolution imaging and spectropolarimetric data at the 1.5-meter GREGOR solar telescope at the Observatorio del Teide, Izaña, Tenerife, Spain. Background-Subtracted Activity Maps (BaSAMs) have been used to locate areas of enhanced activity, Local Correlation Tracking (LCT) provides horizontal proper motions, and near-infrared full-Stokes polarimetry offers access to magnetic fields and line-of-sight velocities. The results show that the decaying active region is characterized by a triangular region between the three leading, positive-polarity sunspots with unfavorable conditions for penumbra formation. This region has a spongy appearance in narrow-band H\(\alpha \) images, shows signs of enhanced activity on small spatial scales, is free of divergence centers and exploding granules, lacks well-ordered horizontal flows, has low flow speeds, and is dominated by horizontal magnetic fields. Umbral cores are inactive, but the interface between pores and penumbral filaments often shows enhanced activity. Moat flows and superpenumbrae are almost always observed, when penumbral filaments are present, even in very small penumbral sectors. However, evidence of the moat flow can also be seen around pores, surviving longer than the decaying penumbral filaments. Light bridges have mainly umbral temperatures, reaching quiet-Sun temperatures in some places, show strong intensity variations, and exhibit weak photospheric horizontal flows, while narrow-band H\(\alpha \) flow maps show substantial inflows.