Transverse motions in sunspot super-penumbral fibrils

TL;DR

This study demonstrates that super-penumbral fibrils in sunspots exhibit ubiquitous transverse motions interpreted as MHD kink waves, providing new insights into wave phenomena and energy transfer in the solar chromosphere.

Contribution

First observational evidence of transverse MHD kink waves in super-penumbral fibrils using high-resolution data, expanding understanding of wave dynamics in sunspot atmospheres.

Findings

Transverse motions are present in over 2000 fibrils.

Wave periods and amplitudes are consistent with quiet Sun chromospheric waves.

Implications for MHD wave energy transfer in sunspot atmospheres.

Abstract

Sunspots have played a key role in aiding our understanding of magnetohydrodynamic (MHD) wave phenomenon in the Sun's atmosphere, and it is well known they demonstrate a number of wave phenomenon associated with slow MHD modes. Recent studies have shown that transverse wave modes are present throughout the majority of the chromosphere. Using high-resolution Ca II 8542 {\AA} observations from the Swedish Solar Telescope, we provide the first demonstration that the chromospheric super-penumbral fibrils, which span out from the sunspot, also show ubiquitous transverse motions. We interpret these motions as transverse waves, in particular the MHD kink mode. We compile the statistical properties of over 2000 transverse motions to find distributions for periods and amplitudes, finding they are broadly consistent with previous observations of chromospheric transverse waves in quiet Sun fibrils. The very presence of the waves in super-penumbral fibrils raises important questions about how they are generated, and could have implications for our understanding of how MHD wave energy is transferred through the atmosphere of a sunspot.