Determination of the chromospheric quiet network element area index and its variation between 2008 and 2011

作     者：Jagdev Singh Ravindra Belur Selvendran Raju Kumaravel Pichaimani Muthu Priyal Thambaje Gopalan Priya Amareswari Kotikalapudi 

作者机构：Indian Institute of AstrophysicsKoramangala 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2012年第12卷第2期

页      面：201-211页

核心收录：

学科分类：0709[理学-地质学] 07[理学] 0708[理学-地球物理学] 070401[理学-天体物理] 0825[工学-航空宇航科学与技术] 0704[理学-天文学] 

主　　题：Sun: network   Sun: Ca K   Sun: solar cycle 

摘      要：In general, it is believed that plages and sunspots are the main contribu- tors to solar irradiance. There are small-scale structures on the Sun with intermediate magnetic fields that could also contribute to solar irradiance, but it has not yet been quantified how many of these small scale structures contribute and how much this varies over the solar cycle. We used Ca II K images obtained from the telescope at the Kodaikanal observatory. We report a method to separate the network elements from the background structure and plage regions, and compute the changes in the network element area index during the minimum phase of the solar cycle and part of the as- cending phase of cycle 24. The measured area occupied by the network elements is about 30% and the plages cover less than 1% of the solar disk during the observation period from February 2008 to 2011. During the extended period of minimum activity, it is observed that the network element area index decreases by about 7% compared to the area occupied by the network elements in 2008. A long term study of the network element area index is required to understand the variations over the solar cycle.