Local sunspot oscillations and umbral dots

TL;DR

This study reveals that local sunspot oscillations are caused by subphotospheric resonators within weak magnetic flux tubes, specifically umbral dots, and are concentrated in small cells with distinct spectra.

Contribution

It introduces a model linking local sunspot oscillations to subphotospheric magnetic flux tubes, especially umbral dots, based on observational data and theoretical analysis.

Findings

Local oscillations occur in small cells with distinct spectra.

Oscillations are linked to subphotospheric magnetic flux tubes.

Weak magnetic fields in tubes are crucial for the observed spectra.

Abstract

Data analysis of sunspot oscillation based on 6-hr SDO run of observation showed that low frequency (0.2 < ! < 1 mHz) oscillations are local similar to three and five minute oscillations. The oscillations in the sunspot are concentrated in cells of a few arcsec, each of which has its own oscillation spectrum. The analysis of two scenario for sunspot oscillations leads to conclusion that local sunspot oscillations occur due to subphotospheric resonator for slow mhd waves. Empirical models of sunspot atmosphere and the theory of slow waves in thin magnetic flux tubes is applied to the modeling of subphotospheric resonator. Spectrum of local oscillations consists of a great number of lines. This kind of spectrum can occur only if the subphospheric resonator is a magnetic tube with a rather weak magnetic field.Magnetic tubes of this sort are umbral dots that appear due to the convective tongues in the monolithic sunspots. The interrelation of local oscillations with umbral dots and wave fronts of traveling waves in sunspots is discussed.