Vol 12, No 2

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

Jagdev Singh, Ravindra Belur, Selvendran Raju, Kumaravel Pichaimani, Muthu Priyal, Thambaje Gopalan Priya, Amareswari Kotikalapudi


Abstract In general, it is believed that plages and sunspots are the main contributors 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 ascending 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.


Keywords Sun: network — Sun: Ca-K — Sun: solar cycle

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