| Name: | Muthu Priyal |
| Affiliation: | Indian Institute of Astrophysics |
| Conference ID : | ASI2024_831 |
| Title : | Temporal and Latitudinal Variations in Ca-K features area derived using ECT: Implication to Meridional Flows |
| Authors : | Muthu Priyal, Jagdev Singh, Ravindra.B |
| Authors Affiliation: | Muthu Priyal, Jagdev Singh, Ravindra. B, Indian Institute of Astrophysics, Bangalore - 560034, India |
| Mode of Presentation: | Poster |
| Abstract Category : | Sun, Solar System, Exoplanets, and Astrobiology |
| Abstract : | The “Equal-Contrast technique” (ECT) methodology is developed to generate uniform long time series of Ca-K images obtained during the 20th century from the Kodaikanal Observatory (KO), Mount Wilson Observatory (MWO) and recent Ca-K filter-grams obtained using narrowband filter at KO and the Mauna Loa Solar Observatory (MLSO). The Correlation Coefficient (CC) for the combined monthly mean Ca-K plage area, derived from the KO, MWO, and Precision Solar Photometric Telescope (at the MLSO) and sunspot numbers is 0.96 for the period 1905–2015.
The variations of plage, EN, AN, and QN area as a function of latitude and time occurs because of meridional flows generated by the dynamo at the base of convection zone and just below the solar surface. We find that large scale active regions appear at Sun’s surface at ∼ 45° latitude at the beginning of solar cycle. We computed the phase differences between the occurrences of maximum activity at between different latitude belts considering the long series of uniform data generated using ECT technique. The values of phase differences indicate that meridional flow has a velocity of about ∼ 9.6 m sec−1 at the 35° latitude belt at the beginning of solar cycle. The speed decreases to ∼ 6, ∼ 4.5, and ∼ 3 m sec−1 at 25° , 15° , and 5° latitude belts. There is no phase difference between the variations of Ca-K activity at 55° , 65° , and 75° latitude belts. The analysis shows that the activity at polar latitude belts is anti-correlated with the sunspot number. These findings point towards the existence of multi-cells in the convection zone. One type of cell could transport the activity from mid-latitude to low-latitude belts through meridional flows and the other one could be operating in the polar region. |
