Transverse oscillations of systems of coronal loops

TL;DR

This paper investigates the collective transverse oscillations of coronal loops using T-matrix theory, revealing how similar densities lead to coupled oscillations and explaining observed loop behaviors.

Contribution

It introduces a theoretical analysis of collective kink modes in coronal loops considering density effects, enhancing understanding of observed oscillation patterns.

Findings

Loops with similar densities oscillate collectively with slightly different frequencies.

Loops with different densities oscillate independently.

The study explains observed antiphase and grouped oscillations in coronal loops.

Abstract

We study the collective kinklike normal modes of a system of several cylindrical loops using the T-matrix theory. Loops that have similar kink frequencies oscillate collectively with a frequency which is slightly different from that of the individual kink mode. On the other hand, if the kink frequency of a loop is different from that of the others, it oscillates individually with its own frequency. Since the individual kink frequency depends on the loop density but not on its radius for typical 1 MK coronal loops, a coupling between kink oscillations of neighboring loops take place when they have similar densities. The relevance of these results in the interpretation of the oscillations studied by \citet{schrijver2000} and \citet{verwichte2004}, in which transverse collective loop oscillations seem to be detected, is discussed. In the first case, two loops oscillating in antiphase are observed; interpreting this motion as a collective kink mode suggests that their densities are roughly equal. In the second case, there are almost three groups of tubes that oscillate with similar periods and therefore their dynamics can be collective, which again seems to indicate that the loops of each group share a similar density. All the other loops seem to oscillate individually and their densities can be different from the rest.