Propagation and Damping of Longitudinal Intensity Oscillations in Solar Coronal Structures

Abstract

Recently, the longitudinal oscillations of intensity have been frequently detected in the different structures of the solar corona using space telescope observations. Some researchers believe that the magneto-acoustic waves, which share the plasma heating processes in the corona, are responsible for the longitudinal oscillations of the intensities. In this study, the aim is to discover the location, generation, propagation and damping of the magneto-acoustic waves in the corona structures as well as to compare the results with theoretical models. For this purpose, for each selected active region, about 400 sequence images are taken at 12 seconds intervals at 171 angstroms using AIA instrument onboard on the SDO space telescope. For each set, the histogram equalization is applied with respect to the first image for all images, then the time series of intensities are extracted from the successive macropixels with 3×3 pixels wide on different paths along the active region loops. Different filters are applied to the time series of the intensities, and real and stable frequencies are identified from the unrealistic and unstable frequencies of the noise in the spectral power density using the Lamb-Scargle algorithm. The physical quantities of the dominant frequencies are computed. The results of this analysis showed that magneto- acoustic waves are produced at the base of the loops of the active regions and propagated along the loops. The range of oscillation period, apparent velocity, apparent length, damping time, and damping quality of these extracted waves are 7-32 minutes, 66-363 km/s; 8-103 mega meters, 0.7-12 minutes and 0.06-0.63, respectively. Also, by comparing the observational results with the theoretical models, the temperature range and electron numerical density of the selected regions are estimated.