On the variation of solar coronal rotation using SDO/AIA observations

Abstract

ABSTRACT We report on the variability of the rotation periods of solar coronal layers with respect to temperature (or height). For this purpose, we have used observations from the Atmospheric Imaging Assembly (AIA) telescope on board the Solar Dynamics Observatory (SDO) space mission of National Aeronautics and Space Administration (NASA). The images used are at wavelengths of 94, 131, 171, 193, 211 and 335 Å during the period from 2012–2018. Analysis of solar full-disc images obtained at these wavelengths by AIA is carried out using the flux modulation method. 17 rectangular strips/bins at equal intervals of 10° (extending from 80°S to 80°N) are selected to extract a time series of extreme ultraviolet (EUV) intensity variations to obtain the autocorrelation coefficient. The peak of the Gaussian fit to the first secondary maximum in the autocorrelogram gives the synodic rotation period. Our analysis shows differential rotation with respect to latitude as well as temperature (or height). In the present study, we find that the sidereal rotation periods of different coronal layers decrease with increasing temperature (or height). The average sidereal rotation period at the lowest temperature (∼600 000 K) corresponding to AIA 171-Å, which originates from the upper transition region/quiet corona, is 27.03 days. The sidereal rotation period decreases with temperature (or height) to 25.47 days at a higher temperature (∼10 million K), corresponding to the flaring regions of the solar corona as seen in AIA 131-Å observations.