Alfvenic tornadoes

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.