Vertical magnetic field on boundary of sunspot umbra

TL;DR

This study investigates the vertical magnetic field at the boundaries of sunspot umbrae, revealing that while the average field remains stable, the vertical component varies significantly, indicating complex magnetic structures.

Contribution

It introduces an independent mathematical method to determine sunspot umbra boundaries and analyzes the vertical magnetic field component along these boundaries.

Findings

Vertical magnetic field varies significantly along the boundary.

Average magnetic field along the boundary remains relatively stable.

Magnetic field structure reflects fibrous penumbral features.

Abstract

12 stable single sunspots were investigated in two aspects. The outer boundaries of the sunspots umbra were determined by an independent mathematical method and the vertical component of the magnetic field at these boundaries was found. We analyzed data from the SDO station using the segments of the continuum and magnetic field. It is shown that in a wide range of sunspot fields, the field average along the contour changes weakly, while the vertical component of the magnetic field itself, in a particular spot, changes significantly along the defined contour which reflects the fibrous structure of the penumbral field.