Alfvenic tornadoes

TL;DR

This paper demonstrates that three-dimensional modified-kinetic Alfvén waves can form Alfvénic tornadoes with plasma density whirls and magnetic flux ropes, supported by solutions resembling Laguerre-Gauss vortex beams.

Contribution

It derives a wave equation for 3D m-KAWs in a magnetoplasma and shows these waves can form vortex structures resembling tornadoes with angular momentum.

Findings

Existence of 3D m-KAW solutions as vortex beams

Formation of plasma density whirls and magnetic flux ropes

Support for Alfvén magnetic flux rope dynamics

Abstract

It is shown that a three-dimensional (3D) modified-kinetic Alfv\'en waves (m-KAWs) can propagate in the form of Alfv\'enic tornadoes characterized by plasma density whirls or magnetic flux ropes carrying orbital angular momentum (OAM). By using the two fluid model, together with Amp\`ere's law, we derive the wave equation for a 3D m-KAWs in a magnetoplasma with $m_e/m_i \ll \beta \ll 1$, where $m_e$ $(m_i)$ is the electron (ion) mass, $\beta =4 \pi n_0 k_B (T_e + T_i)/B_0^2$, $n_0$ the unperturbed plasma number density, $k_B$ the Boltzmann constant, $T_e (T_e)$ the electron (ion) temperature, and $B_0$ the strength of the ambient magnetic field. The 3D m-KAW equation admits solutions in the form of a Laguerre-Gauss (LG) Alfv\'enic vortex beam or Alfv\'enic tornadoes with plasma density whirls that support the dynamics of Alfv\'en magnetic flux ropes.