On the Source of Propagating Slow Magneto-acoustic Waves in Sunspots

TL;DR

This study shows that slow magneto-acoustic waves in sunspots are externally driven by photospheric p-modes, with amplitude modulations observed across different atmospheric layers, indicating a connection between surface oscillations and coronal wave activity.

Contribution

It provides evidence that propagating slow magneto-acoustic waves in sunspots originate from external photospheric p-modes, clarifying their source and propagation mechanism.

Findings

Waves are externally driven by photospheric p-modes.

Amplitude modulations are consistent across atmospheric layers.

Waves dissipate after propagating into the corona.

Abstract

Recent high-resolution observations of sunspot oscillations using simultaneously operated ground- and space-based telescopes reveal the intrinsic connection between different layers of the solar atmosphere. However, it is not clear whether these oscillations are externally driven or generated in-situ. We address this question by using observations of propagating slow magneto-acoustic waves along a coronal fan loop system. In addition to the generally observed decreases in oscillation amplitudes with distance, the observed wave amplitudes are also found to be modulated with time, with similar variations observed throughout the propagation path of the wavetrain. Employing multi-wavelength and multi-instrument data we study the amplitude variations with time as the waves propagate through different layers of the solar atmosphere. By comparing the amplitude-modulation period in different layers, we find that slow magneto-acoustic waves observed in sunspots are externally driven by photospheric p-modes, which propagate upwards into the corona before becoming dissipated.