On collective nature of non-linear torsional Alfvén waves

ABSTRACT Torsional Alfvén waves in coronal plasma loops are usually considered to be non-collective, i.e. consist of cylindrical surfaces evolving independently, which significantly complicates their detection observations. This non-collective nature, however, can get modified the non-linear regime. To address this question, propagation torsional straight magnetic flux tubes has been investigated numerically using astrophysical MHD code Athena++ and analytically, support numerical results, perturbation theory up second order. Numerical results have revealed that there is radially uniform-induced density whose uniformity does not depend on radial structure mother wave. Our analysis showed ponderomotive force leads induction axial velocity perturbations, while mechanism for provided by a non-equal elasticity tube directions. The latter qualitatively understood interplay between wave external medium, boundary conditions. amplitude these non-linearly induced perturbations found determined driver squared parameter β. existence collective uniform accompanying could as an additional observational signature upper layers solar atmosphere.