Behaviour of oscillations in loop structures above active regions

TL;DR

This study combines multiwavelength solar observations to analyze oscillation behaviors across different atmospheric layers, revealing propagation patterns, magnetic field inclinations, and their relation to solar structures.

Contribution

It provides new insights into the propagation of oscillations from the photosphere to the corona and estimates magnetic tube inclinations in sunspots using observational data.

Findings

Low-frequency oscillations align with coronal fan structures.

High-frequency oscillations propagate along magnetic field lines.

Magnetic tube inclination near sunspot boundaries is approximately 40 degrees.

Abstract

In this study we combine the multiwavelength ultraviolet -- optical (Solar Dynamics Observatory, SDO) and radio (Nobeyama Radioheliograph, NoRH) observations to get further insight into space-frequency distribution of oscillations at different atmospheric levels of the Sun. We processed the observational data on NOAA 11711 active region and found oscillations propagating from the photospheric level through the transition region upward into the corona. The power maps of low-frequency (1--2 mHz) oscillations reproduce well the fan-like coronal structures visible in the Fe ix 171A line. High frequency oscillations (5--7 mHz) propagate along the vertical magnetic field lines and concentrate inside small-scale elements in the umbra and at the umbra-penumbra boundary. We investigated the dependence of the dominant oscillation frequency upon the distance from the sunspot barycentre to estimate inclination of magnetic tubes in higher levels of sunspots where it cannot be measured directly, and found that this angle is close to 40 degrees above the umbra boundaries in the transition region.