Observations of upward propagating waves in the transition region and corona above Sunspots

TL;DR

This paper reports on observations of upward propagating waves and oscillations in sunspot regions, revealing their properties and suggesting they are driven by shocks and magnetic-acoustic waves, enhancing understanding of solar atmospheric dynamics.

Contribution

It provides new detailed measurements of oscillations and disturbances in sunspot regions, linking transition region oscillations to shock-driven processes and coronal plasma flows.

Findings

Oscillations show 3-minute periods with non-damped cyclic motions.

Upward propagating disturbances have velocities of 30-80 km/s.

Intensity variations indicate nonlinear oscillations and shock-driven plasma flows.

Abstract

We present observations of persistent oscillations of some bright features in the upper-chromosphere/transition-region above sunspots taken by IRIS SJ 1400 {\AA} and upward propagating quasi-periodic disturbances along coronal loops rooted in the same region taken by AIA 171 {\AA} passband. The oscillations of the features are cyclic oscillatory motions without any obvious damping. The amplitudes of the spatial displacements of the oscillations are about 1 $^{"}$. The apparent velocities of the oscillations are comparable to the sound speed in the chromosphere, but the upward motions are slightly larger than that of the downward. The intensity variations can take 24-53% of the background, suggesting nonlinearity of the oscillations. The FFT power spectra of the oscillations show dominant peak at a period of about 3 minutes, in consistent with the omnipresent 3 minute oscillations in sunspots. The amplitudes of the intensity variations of the upward propagating coronal disturbances are 10-15% of the background. The coronal disturbances have a period of about 3 minutes, and propagate upward along the coronal loops with apparent velocities in a range of 30-80 km/s. We propose a scenario that the observed transition region oscillations are powered continuously by upward propagating shocks, and the upward propagating coronal disturbances can be the recurrent plasma flows driven by shocks or responses of degenerated shocks that become slow magnetic-acoustic waves after heating the plasma in the coronal loops at their transition-region bases.