Conference ID : ASI2022_238
Title : Study of Chromospheric Differential Rotation of the Sun using Ca II K Data
Authors : Dibya Kirti Mishra, Bibhuti Kumar Jha, Subhamoy Chatterjee and Dipankar Banerjee
Abstract Type: Oral
Abstract Category : Sun and the Solar System
Abstract : The purpose of this project is to study the differential rotation in the chromospheric layer in order to get an idea about the coupling between different layers of the sun. For our purpose we used digitized and calibrated full disc Ca II K (3933.67 Å) images of Kodaikanal Solar Observatory data (1907-2007) . We tracked plages and network features all over the disc using automated technique for the same. First heliocentric images were converted into heliographic images by taking 1 pixel = 0.1 degree accuracy. We then compared two images consecutively for 100 years of data by taking a 5 ° latitude bin and taking the difference of two latitude bin portions of images of two different days in which one image was shifted in a particular range. Root Mean Square (rms) of that difference was taken and the longitudinal shift value corresponding to the minima of that rms was noted and repeated for all the latitude bins. For every latitude bin we calculated angular rotation rate Ω . After getting a value of Ω for each pair of images we have taken the mean for all the measurements in each bin and then we applied the least square method for fitting to get A (equatorial rotation rate) , B and C (latitudinal differential rotation rate). Also we compared our result with white light result and Bertello et al. (2016) Ca II K result. We also found the variation in A and B with cycle number and cycle strength.