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Sunspots, seen as dark spots in white-light images, are areas with concentrated magnetic fields. In magnetograms, they appear as two regions of opposite polarity close to each other. Therefore, sunspots in white-light images are essentially the two poles of a broader feature known as bipolar magnetic regions (BMR). Typically, sunspots are tilted relative to the equator, a phenomenon known as the tilt angle. Statistically, the relationship between average tilt angle and latitude is known as Joy's law, which states that the average tilt angle increases with latitude (Hale et al. 1919). The tilt angles of BMRs/sunspots are crucial for solar-dynamo models. Kodaikanal Solar Observatory (KSO) has a long history of making solar observations in three different wavelengths: white light, Ca-II K, and H-alpha. In this project, we have utilized the white-light data from KSO. Using a semi-automatic method, we identify sunspot groups. Based on the sunspot group information, we calculated tilt angles for the period of 1923-1946 using the traditional method described by Howard (1992). The results arising from this study will be discussed.
Board of Graduate Studies