Magnetic connectivity between the light bridge and penumbra in a sunspot

Abstract

A light bridge is a prominent structure commonly observed within a sunspot. Its presence usually triggers a wealth of dynamics in a sunspot, and has a lasting impact on sunspot evolution. However, the fundamental structure of light bridges is still not well understood. In this study, we used the high-resolution spectropolarimetry data obtained by the Solar Optical Telescope onboard the Hinode satellite to analyze the magnetic and thermal structure of a light bridge at \AR. We also combined the high-cadence $1700\unitÅ$ channel data provided by the Atmospheric Imaging Assembly onboard the Solar Dynamic Observatory to study the dynamics on this bridge. We found that a pair of blue and red Doppler shift patches at two ends of this bridge, this pattern appears to be the convective motion directed by the horizontal component of the magnetic field aligned with the spine of this bridge. Paired upward and downward motions implies that the light bridge could have a two-legged or undulate magnetic field. Significant four minute oscillations in the emission intensity of the $1700\unitÅ$ bandpass were detected at two ends, which had overlap with the paired blue and red shift patches. The oscillatory signals at the light bridge and the penumbra were highly correlated with each other. Although they are separated in space at the photosphere, the periodicity seems to have a common origin from the underneath. Therefore, we infer that the light bridge and penumbra could share a common magnetic source and become fragmented at the photosphere by magneto-convection.

arXiv comment8 pages, 4 figures, accepted for ApJL

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Cited by in corpus (6)

• Detection of flare multi-periodic pulsations in mid-ultraviolet Balmer continuum, Ly-alpha, hard X-ray, and radio emissions simultaneously
• Doppler shift oscillations of a sunspot detected by CYRA and IRIS
• On the formation height of low-corona and chromospheric channels of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO)
• Small-scale Bright Blobs Ejected from a Sunspot Light Bridge
• Light Bridges Can Suppress the Formation of Coronal Loops
• Apparent Transverse Motion of Light Bridges Coupled to Coronal Loop Dynamics