Umbral Fine Structures in Sunspots Observed with Hinode Solar Optical Telescope

TL;DR

This study uses high-resolution Hinode SOT imaging to analyze sunspot umbral fine structures, focusing on umbral dots' properties, dynamics, and their relation to magnetoconvection in strong magnetic fields.

Contribution

First detailed analysis of umbral dot properties and their temporal evolution using space-based high-resolution imaging.

Findings

Umbral dots' brightness depends on surrounding background brightness.

Several UDs exhibit fission and fusion behaviors.

Properties of umbral structures support magnetoconvection models.

Abstract

High resolution imaging observation of a sunspot umbra was done with Hinode Solar Optical Telescope (SOT). Filtergrams in wavelengths of blue and green continuum were taken during three consecutive days. The umbra consisted of a dark core region, several diffuse components and numerous umbral dots. We derived basic properties of umbral dots (UDs), especially their temperatures, lifetimes, proper motions, spatial distribution and morphological evolution. Brightness of UDs is confirmed to depend on the brightness of their surrounding background. Several UDs show fission and fusion. Thanks to the stable condition of space observation, we could first follow the temporal behavior of these events. The derived properties of internal structure of the umbra are discussed in viewpoint of magnetoconvection in a strong magnetic field.