The period ratio P_1/P_2 of torsional Alfv\'en waves with steady flows in spicules

TL;DR

This paper models standing torsional Alfvén waves in solar spicules considering density stratification, magnetic expansion, and steady flows, explaining observed deviations in period ratios from theoretical expectations.

Contribution

It introduces a cylindrical model incorporating steady flows and plasma-beta effects to analyze torsional wave period ratios in spicules, advancing understanding of solar atmospheric dynamics.

Findings

Steady flows cause shifts in the period ratio P_1/P_2.

The model explains deviations of observed period ratios from 2.

Eigenfrequencies and eigenfunctions are derived for finite plasma-beta.

Abstract

The aim here is to model the standing torsional oscillations in solar spicules in the presence of density stratification, magnetic field expansion, and steady flows. By implementing cylindrical geometry, the eigenfrequencies, eigenfunctions, and the period ratio P_1/P_2 of these waves is obtained for finite plasma-beta. The shifts created by the steady flow justifies the divergence of the observed period ratio for the first and second periods from the number 2.