Variation of coronal holes latitudinal distribution: Correction of limb brightening of EUV coronal images
Chargeishvili, B. B.; Maghradze, D. A.; Japaridze, D. R.; Oghrapishvili, N. B.; Mdzinarishvili, T. G.; Chargeishvili, K. B.; Shergelashvili, B. M.
Georgia, Austria
Abstract
We studied the limb brightening of SOHO EIT daily images of the solar corona taken in 195 Å wavelength line from 1996 to 2018. Using special software, we studied the distribution of the background intensity of the entire disk in the direction of rotation (horizontally) and perpendicular to the direction of rotation (vertical). The study shows that the intensity distribution from the center to the limb of the solar disk is not polar-symmetric. A data-derived study showed that the coronal limb brightening has rather elliptical than circular isophotes. The pattern of the limb brightening correlates with the cycle of solar activity. The moving average patterns with the window of the year give good results for removing the limb brightening when preparing coronal images for further study.