Dynamics of a multi-thermal loop in the solar corona^⋆

¹ Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, UK
e-mail: g.nistico@warwick.ac.uk
² Institute of Solar-Terrestrial Physics, Russian Academy of Science, Siberian Branch, 126a Lermontov st., 664033 Irkutsk, Russia
e-mail: anfinogentov@iszf.irk.ru
³ Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences, 196140 St. Petersburg, Russia
⁴ School of Space Research, Kyung Hee University, Yongin, 446-701 Gyeonggi, Korea

Received: 9 April 2014
Accepted: 2 July 2014

Abstract

Context. We present an observation of a long-living multi-thermal coronal loop, visible in different extreme ultra-violet wavebands of SDO/AIA in a quiet-Sun region close to the western solar limb.

Aims. Analysis of persistent kink displacements of the loop seen in different bandpasses that correspond to different temperatures of the plasma allows sub-resolution structuring of the loop to be revealed.

Methods. A vertically oriented slit is taken at the loop top, and time-distance maps are made from it. Loop displacements in time-distance maps are automatically tracked with the Gaussian fitting technique and fitted with a sinusoidal function that is “guessed”. Wavelet transforms are further used in order to quantify the periodicity variation in time of the kink oscillations.

Results. The loop strands are found to oscillate with the periods ranging between 3 and 15 min. The oscillations are observed in intermittent regime with temporal changes in the period and amplitude. The oscillations are different at three analysed wavelengths.

Conclusions. This finding suggests that the loop-like threads seen at different wavelengths are not co-spatial, hence that the loop consists of several multi-thermal strands. The detected irregularity of the oscillations can be associated with a stochastic driver acting at the footpoints of the loop.