Multilevel Analysis of Oscillation Motions in Active Regions of the Sun

TL;DR

This study combines optical and radio observations to analyze oscillation motions in solar active regions, revealing wave propagation and multiple oscillation periods with high instability and a time delay between data types.

Contribution

It introduces a novel multi-wavelength analysis method for studying oscillations in sunspots, highlighting wave dynamics and temporal delays in the solar atmosphere.

Findings

Detected three-minute oscillations in sunspot umbra with high spectral similarity.

Found a 50-second time delay indicating upward MHD wave propagation.

Identified longer-period oscillations at 8 and 15 minutes in both data sets.

Abstract

We present a new method that combines the results of an oscillation study made in optical and radio observations. The optical spectral measurements in photospheric and chromospheric lines of the line-of-sight velocity were carried out at the Sayan Solar Observatory. The radio maps of the Sun were obtained with the Nobeyama Radioheliograph at 1.76 cm. Radio sources associated with the sunspots were analyzed to study the oscillation processes in the chromosphere-corona transition region in the layer with magnetic field B=2000 G. A high level of instability of the oscillations in the optical and radio data was found. We used a wavelet analysis for the spectra. The best similarities of the spectra of oscillations obtained by the two methods were detected in the three-minute oscillations inside the sunspot umbra for the dates when the active regions were situated near the center of the solar disk. A comparison of the wavelet spectra for optical and radio observations showed a time delay of about 50 seconds of the radio results with respect to optical ones. This implies a MHD wave traveling upward inside the umbral magnetic tube of the sunspot. Besides three-minute and five-minute ones, oscillations with longer periods (8 and 15 minutes) were detected in optical and radio records.