Abstract

Ever since their detection two decades ago, standing kink oscillations in coronal loops have been extensively studied both observationally and theoretically. Almost all driven coronal loop oscillations (e.g., by flares) are observed to damp through time often with Gaussian or exponential profiles. Intriguingly, however, it has been shown theoretically that the amplitudes of some oscillations could be modified from Gaussian or exponential profiles if cooling is present in the coronal loop systems. Indeed, in some cases the oscillation amplitude can even increase through time. In this article, we analyse a flare-driven coronal loop oscillation observed by the Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA) in order to investigate whether models of cooling can explain the amplitude profile of the oscillation and whether hints of cooling can be found in the intensity evolution of several SDO/AIA filters. During the oscillation of this loop system, the kink mode amplitude appears to differ from a typical Gaussian or exponential profile with some hints being present that the amplitude increases. The application of cooling coronal loop modelling allowed us to estimate the density ratio between the loop and the background plasma, with a ratio of between 2.05-2.35 being returned. Overall, our results indicate that consideration of the thermal evolution of coronal loop systems can allow us to better describe oscillations in these structures and return more accurate estimates of the physical properties of the loops (e.g., density, scale height, magnetic field strength).

Highlights

  • Standing kink oscillations were first observed in coronal loops by Aschwanden et al (1999) and Nakariakov et al (1999) using high-resolution imaging data collected by the Transition Region And Coronal Explorer (TRACE; Handy et al, 1999)

  • Those authors found that a flare in the local Active Region (AR) caused the magnetic field guide of the coronal loop to shake from side-toside in a manner analogous to oscillations of a guitar string

  • Ignoring any further errors introduced through the loop fitting is justified in this case, as our study aims to show, in principle, that including the effects of cooling could have important implications for coronal loop modeling

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Summary

Introduction

Standing kink oscillations were first observed in coronal loops by Aschwanden et al (1999) and Nakariakov et al (1999) using high-resolution imaging data collected by the Transition Region And Coronal Explorer (TRACE; Handy et al, 1999). One of the most interesting aspects of kink oscillations in coronal loops was their rapid damping profiles, with many examples of flare-driven coronal loop oscillations damping to sub-resolution spatial scales within two or three periods Such damping has been explained through a number of physical mechanisms, such as resonant absorption (e.g., Goossens et al, 2002; Ruderman and Roberts, 2002), phase mixing, and foot-point damping. It has been shown analytically that it is possible that some driven coronal loops could oscillate and damp in a manner not adequately modeled by Gaussian nor exponential profiles through time

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