Observation of kink waves and their reconnection-like origin in solar spicules

TL;DR

This study observes kink waves propagating in solar spicules, identifies their increasing oscillation periods with height, and suggests small-scale magnetic reconnection at the spicule base as their origin, contributing to understanding solar atmospheric dynamics.

Contribution

It provides direct observational evidence linking small-scale magnetic reconnection to the excitation of kink waves in solar spicules, highlighting their role in solar atmospheric processes.

Findings

Kink waves propagate along spicules with a mean period of ~175 s.

Oscillation periods increase linearly with height, acting as a low pass filter.

Signatures of small-scale magnetic reconnection are observed at spicule bases.

Abstract

We analyze the time series of Ca II H-line obtained from Hinode/SOT on the solar limb. We follow three cases of upwardly propagating kink waves along a spicule and inverted Y-shaped structures at the cusp of it. The time-distance analysis shows that the axis of spicule undergoes quasi-periodic transverse displacement at different heights from the photosphere. The mean period of transverse displacement is ~ 175 s and the mean amplitude is 1 arc\,sec. The oscillation periods are increasing linearly with height which may be counted as the signature that the spicule is working as a low pass filter and allows only the low frequencies to propagate towards higher heights. The oscillations amplitude is increasing with height due to decrease in density. The phase speeds are increasing until some heights and then decreasing which may be related to the small scale reconnection at the spicule basis. We conclude that transversal displacement of spicules axis can be related to the propagation of kink waves along them. Moreover, we observe signatures of small-scale magnetic reconnection at the cusp of spicules which may excite kink waves.