Spectropolarimetery of umbral fine structures from Hinode: Evidence for magnetoconvection

TL;DR

This study uses spectropolarimetric data from Hinode to analyze umbral fine structures, revealing evidence of magnetoconvection through detailed magnetic and flow patterns in umbral dots and light bridges.

Contribution

It provides new observational evidence of magnetoconvection in sunspot umbrae by analyzing magnetic fields, flows, and temperature structures with high-resolution spectropolarimetry.

Findings

Umbral dots show upflows and magnetic field weakening in their centers.

Larger umbral dots exhibit downflows and stronger magnetic fields at their edges.

Magnetic field inclination forms cusp structures above umbral features.

Abstract

We present spectropolarimetric analysis of umbral dots and a light bridge fragment that show dark lanes in G-band images. Umbral dots show upflow as well as associated positive Stokes V area asymmetry in their central parts. Larger umbral dots show down flow patches in their surrounding parts that are associated with negative Stokes V area asymmetry. Umbral dots show weaker magnetic field in central part and higher magnetic field in peripheral area. Umbral fine structures are much better visible in total circularly polarized light than in continuum intensity. Umbral dots show a temperature deficit above dark lanes. The magnetic field inclination show a cusp structure above umbral dots and a light bridge fragment. We compare our observational findings with 3D magnetohydrodynamic simulations.