Vigorous convection in a sunspot granular light bridge

Abstract

Light bridges are the most prominent manifestation of convection in sunspots. The brightest representatives are granular light bridges composed of features that appear to be similar to granules. An in-depth study of the convective motions, temperature stratification, and magnetic field vector in and around light bridge granules is presented with the aim of identifying similarities and differences to typical quiet-Sun granules. Spectropolarimetric data from the Hinode Solar Optical Telescope were analyzed using a spatially coupled inversion technique to retrieve the stratified atmospheric parameters of light bridge and quiet-Sun granules. Central hot upflows surrounded by cooler fast downflows reaching 10 km/s clearly establish the convective nature of the light bridge granules. The inner part of these granules in the near surface layers is field free and is covered by a cusp-like magnetic field configuration. We observe hints of field reversals at the location of the fast downflows. The quiet-Sun granules in the vicinity of the sunspot are covered by a low-lying canopy field extending radially outward from the spot. The similarities between quiet-Sun and light bridge granules point to the deep anchoring of granular light bridges in the underlying convection zone. The fast, supersonic downflows are most likely a result of a combination of invigorated convection in the light bridge granule due to radiative cooling into the neighboring umbra and the fact that we sample deeper layers, since the downflows are immediately adjacent to the slanted walls of the Wilson depression.

10 pages, 11 figures

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• Magneto-convection in a sunspot umbra
• Penumbral structure and outflows in simulated sunspots
• The origin of the reversed granulation in the solar photosphere
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Cited by in corpus (22)

• The European Solar Telescope
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• Oscillating light wall above a sunspot light bridge
• Deep probing of the photospheric sunspot penumbra: no evidence for magnetic field-free gaps
• Internetwork magnetic field as revealed by 2D inversions
• Active region fine structure observed at 0.08 arcsec resolution
• The influence of NLTE effects in Fe I lines on an inverted atmosphere I. 6301 A and 6302 A lines formed in 1D NLTE
• Abnormal oscillation modes in a waning light bridge
• Observational Evidence of a Flux Rope within a Sunspot Umbra
• Three-dimensional magnetic structure of a sunspot: comparison of the photosphere and upper chromosphere
• The formation of an atypical sunspot light bridge as a result of large-scale flux emergence
• Magnetic filed dynamics and varying plasma emission in large coronal loops
• Sunspot Light Walls Suppressed by Nearby Brightenings
• Sunspot penumbral filaments intruding into a light bridge and the resultant reconnection jets
• Signatures of the impact of flare ejected plasma on the photosphere of a sunspot light-bridge
• Structure of sunspot light bridges in the chromosphere and transition region
• Changes in granulation scales over the solar cycle seen with SDO/HMI and Hinode/SOT
• Long-Term Evolution of Three Light Bridges Developed on the Same Sunspot
• Light Bridges Can Suppress the Formation of Coronal Loops
• Various Activities above Sunspot Light Bridges in IRIS Observations: Classification and Comparison
• Simultaneous spectropolarimetric observations in the H$\alpha$ and Ca II 8662 Å lines of an active region