On the plasma flow inside magnetic tornadoes on the Sun

TL;DR

This paper investigates the structure and dynamics of magnetic tornadoes on the Sun, combining high-resolution observations and simulations to understand how vortex flows drive plasma rotation from the photosphere to the corona.

Contribution

It demonstrates that magnetic tornadoes are caused by stacked vortex flows and shows that particle trajectories follow spirals, depending on atmospheric location and magnetic field strength.

Findings

Magnetic tornadoes are driven by stacked vortex flows from the photosphere to the corona.

Particle trajectories in simulated tornadoes follow spirals.

The properties of plasma trajectories depend on atmospheric height and magnetic field strength.

Abstract

High-resolution observations with the Swedish 1-m Solar Telescope (SST) and the Solar Dynamics Observatory (SDO) reveal rotating magnetic field structures that extend from the solar surface into the chromosphere and the corona. These so-called magnetic tornadoes are primarily detected as rings or spirals of rotating plasma in the Ca II 854.2 nm line core (also known as chromospheric swirls). Detailed numerical simulations show that the observed chromospheric plasma motion is caused by the rotation of magnetic field structures, which again are driven by photospheric vortex flows at their footpoints. Under the right conditions, two vortex flow systems are stacked on top of each other. We refer to the lower vortex, which extends from the low photosphere into the convection zone, as intergranular vortex flow (IVF). Once a magnetic field structure is co-located with an IVF, the rotation is mediated into the upper atmospheric layers and an atmospheric vortex flow (AVF, or magnetic tornado) is generated. In contrast to the recent work by Shelyag et al., we demonstrate that particle trajectories in a simulated magnetic tornado indeed follow spirals and argue that the properties of the trajectories decisively depend on the location in the atmosphere and the strength of the magnetic field.