Open AccessVariation in Solar Limb Darkening Coefficient Estimated from Solar Images Taken by SOHO and SDO
Author(s) -
Byeongha Moon,
Dong-Gwon Jeong,
Suyeon Oh,
Jin-Hun Sohn
Publication year - 2017
Publication title -
journal of astronomy and space sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.273
H-Index - 11
eISSN - 2093-5587
pISSN - 2093-1409
DOI - 10.5140/jass.2017.34.2.99
Subject(s) - limb darkening , physics , intensity (physics) , observatory , solar minimum , astrophysics , sunlight , atmospheric sciences , optics , solar cycle , plasma , stars , quantum mechanics , solar wind
The sun is not equally bright over the whole sphere, but rather is darkened toward the limb. This effect is well-known as\udlimb darkening. The limb darkening coefficient is defined by the ratio of the center intensity to limb intensity. In this study,\udwe calculate the limb darkening coefficient using the photospheric intensity estimated from solar images taken by solar and\udhelispheric observatory (SOHO) and solar dynamics observatory (SDO). The photospheric intensity data cover almost two\udsolar cycles from May 1996 to December 2016. The limb darkening coefficient for a size of 0.9 diameter is about 0.69 and\udthis value is consistent with solar limb darkening. The limb darkening coefficient estimated from SOHO shows a temporal\udincrease at solar maximum and a gradual increase since the solar minimum of 2008. The limb darkening coefficient\udestimated from SDO shows a constant value of about 0.65 and a decreasing trend since 2014. The increase in the coefficient\udreflects the effect of weakened solar activity. However, the decrease since 2014 is caused by the aging effect