Long-term variation of sunspot penumbra to umbra area ratio: A study using Kodaikanal white-light Digitized Data

Bibhuti Kumar Jha, Sudip Mandal, Dipankar Banerjee

A typical sunspot, as seen in white-light intensity images, has a two part structure: a dark umbra and a lighter penumbra. Such distinction primarily arises due to the different or…