Solar Active Longitudes From Kodaikanal White-light Digitized Data
  The study of solar active longitudes has generated a great interest in the recent years. In this work we have used an unique continuous sunspot data series obtained from Kodaikanal observatory and revisited the problem. Analysis of the data shows a persistent presence of the active longitude during the whole 90 years of data duration. We compare two well studied analysis methods and presented their respective results. The separation between the two most active longitudes is found be roughly 180{\deg} for majority of time. Additionally, we also find a comparatively weaker presence of separations at 90{\deg} and 270{\deg}. Migration pattern of these active longitudes as revealed from our data is found to be consistent with the solar differential rotation curve. We also study the periodicities in the active longitudes and found two dominant periods of $\approx$1.3 years and $\approx$2.2 years. These periods, also found in other solar proxies, indicate their relation with the global solar dynamo mechanism. 
Sudip Mandal, Subhamoy Chatterjee, Dipankar Banerjee
astro-ph.SR