Probing spectral line asymmetries due to the propagating transverse waves in the solar corona

TL;DR

This study uses 3D MHD simulations and forward modeling to show that transverse waves in the solar corona produce detectable spectral line asymmetries, revealing a new diagnostic for wave-induced turbulence.

Contribution

It demonstrates that transverse MHD waves cause observable spectral asymmetries, linking wave dynamics to spectroscopic signatures in the solar corona.

Findings

Transverse waves induce alternating red and blue asymmetries in spectral lines.

Asymmetries reach up to 20% of peak intensity and velocities of 30-40 km/s.

Signatures are detectable with current DKIST instrument capabilities.

Abstract

Decades-long studies of asymmetric spectral lines in the solar corona suggest mass and energy transport from lower atmospheric layers to the corona. While slow magnetoacoustic waves and plasma flows are recognized as drivers of these spectral line asymmetries, the role of transverse MHD waves remains largely unexplored. Previous simulations have shown that unidirectionally propagating kink waves, in the presence of perpendicular density inhomogeneities, can produce a turbulence-like phenomenon called ``uniturbulence''. However, the spectroscopic signatures of this effect have not been investigated until now. Due to varying Doppler shifts from the plasma elements with different emissions, we expect to observe signatures of both blueward and redward asymmetries. Past instruments like EIS may have missed these signatures due to resolution limitations, but current instruments like DKIST offer a better opportunity for detection. We conducted 3D MHD simulations of transverse waves in a polar plume with density inhomogeneities and performed forward modeling for the Fe XIII emission line at 10749 \AA. Our findings show that transverse waves and uniturbulence induce alternating red and blueward asymmetries, with magnitudes reaching up to 20\% of peak intensity and secondary peak velocities between 30 and 40 km s$^{-1}$, remaining under 100 km s$^{-1}$. These asymmetries propagate with the transverse waves, and even at DKIST resolution, similar signatures can be detected. Our study suggests that spectral line asymmetries can serve as a diagnostic tool for detecting transverse wave-induced uniturbulence.