Magnetic swirls and associated fast magnetoacoustic kink waves in a solar chromospheric flux tube

TL;DR

This paper uses 3D magnetohydrodynamic simulations to study how impulsively generated magnetic swirls in solar flux tubes excite magnetoacoustic kink and Alfvén waves, revealing energy transfer mechanisms in the solar chromosphere and corona.

Contribution

It demonstrates the generation of specific wave modes and magnetic swirl patterns in flux tubes triggered by localized velocity pulses, advancing understanding of solar atmospheric dynamics.

Findings

Dipole-like swirls associated with kink and Alfvén waves are generated.

Energy transfer to chromosphere and corona is sufficient to offset losses.

Numerical results match some observational signatures.

Abstract

We perform numerical simulations of impulsively generated magnetic swirls in an isolated flux tube which is rooted in the solar photosphere. These swirls are triggered by an initial pulse in a horizontal component of the velocity. The initial pulse is launched either: (a) centrally, within the localized magnetic flux tube; or (b) off-central, in the ambient medium. The evolution and dynamics of the flux tube is described by three-dimensional, ideal magnetohydrodynamic equations. These equations are numerically solved to reveal that in case (a) dipole-like swirls associated with the fast magnetoacoustic kink and $m=1$ Alfv\'en waves are generated. In case (b), the fast magnetoacoustic kink and $m=0$ Alfv\'en modes are excited. In both these cases, the excited fast magnetoacoustic kink and Alfv\'en waves consist of similar flow pattern and magnetic shells are also generated with clockwise and counter-clockwise rotating plasma within them, which can be the proxy of dipole-shaped chromospheric swirls. The complex dynamics of vortices and wave perturbations reveals the channelling of sufficient amount of energy to fulfill energy losses in the chromosphere ($\sim$ 10$^{4}$ W m$^{-1}$) and in the corona ($\sim$ 10$^{2}$ W m$^{-1}$). Some of these numerical findings are reminiscent of signatures in recent observational data.