Variations of the Ca II K Line Profile Parameters with Solar Latitude and Time Observed from Kodaikanal Solar Observatory
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| Natura: | Preprint |
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2025
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| author | Srinivasa, Apoorva Sreedevi, Anu Raju, K P Nagaraju, K Singh, Jagdev Karuppath, Narayanankutty Devendran, P Kumar, T Ramesh Kumaravel, P |
| author_facet | Srinivasa, Apoorva Sreedevi, Anu Raju, K P Nagaraju, K Singh, Jagdev Karuppath, Narayanankutty Devendran, P Kumar, T Ramesh Kumaravel, P |
| contents | The Calcium-K line profiles as functions of solar latitude and time were obtained through our observations from the Kodaikanal Solar Observatory using the solar tunnel telescope and spectrograph with a CCD detector. Observations were conducted on all days with favourable sky conditions. We analysed the data collected over a period of about ten years to study the variations in the Ca II K line profiles recorded between 2015 and 2024, of which 709 days of data were found useful. The temporal and time-averaged latitudinal variations of the K$_{1}$ width, K$_{2}$ width, K$_{3}$ intensity and the intensity ratios of K$_{2v}$/K$_{2r}$ and K$_{2v}$/K$_{3}$ were computed using a semi-automated program. The parameters showed asymmetric increases towards the higher latitudes, with the rates of increase being higher in the southern hemisphere. The temporal plots for K$_{1}$ width and K$_{3}$ intensity showed positive correlations with the plage and spot filling factors, whereas the temporal plots for K$_{2}$ width, K$_{2v}$/K$_{2r}$ and K$_{2v}$/K$_{3}$ intensity ratios showed negative correlations. The time-averaged latitudinal plot for K$_{1}$ width has small peaks near 25°N and 20°S. The K$_{2}$ width has a small peak at 0°. The K$_{3}$ intensity has peaks at 20°N and 15°S. The K$_{2v}$/K$_{2r}$ intensity ratio shows peaks at 50$\degree$N, 0° and 40°S. The K$_{2v}$/K$_{3}$ intensity ratio shows peaks at 60°N, 0° and 60°S. Slope profiles show spectral response to magnetic activity peaks near K$_{3}$ with north-south asymmetries. Such variations in the line profiles are important in the studies of solar irradiance, surface flux transport and solar dynamo. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_14609 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Variations of the Ca II K Line Profile Parameters with Solar Latitude and Time Observed from Kodaikanal Solar Observatory Srinivasa, Apoorva Sreedevi, Anu Raju, K P Nagaraju, K Singh, Jagdev Karuppath, Narayanankutty Devendran, P Kumar, T Ramesh Kumaravel, P Solar and Stellar Astrophysics The Calcium-K line profiles as functions of solar latitude and time were obtained through our observations from the Kodaikanal Solar Observatory using the solar tunnel telescope and spectrograph with a CCD detector. Observations were conducted on all days with favourable sky conditions. We analysed the data collected over a period of about ten years to study the variations in the Ca II K line profiles recorded between 2015 and 2024, of which 709 days of data were found useful. The temporal and time-averaged latitudinal variations of the K$_{1}$ width, K$_{2}$ width, K$_{3}$ intensity and the intensity ratios of K$_{2v}$/K$_{2r}$ and K$_{2v}$/K$_{3}$ were computed using a semi-automated program. The parameters showed asymmetric increases towards the higher latitudes, with the rates of increase being higher in the southern hemisphere. The temporal plots for K$_{1}$ width and K$_{3}$ intensity showed positive correlations with the plage and spot filling factors, whereas the temporal plots for K$_{2}$ width, K$_{2v}$/K$_{2r}$ and K$_{2v}$/K$_{3}$ intensity ratios showed negative correlations. The time-averaged latitudinal plot for K$_{1}$ width has small peaks near 25°N and 20°S. The K$_{2}$ width has a small peak at 0°. The K$_{3}$ intensity has peaks at 20°N and 15°S. The K$_{2v}$/K$_{2r}$ intensity ratio shows peaks at 50$\degree$N, 0° and 40°S. The K$_{2v}$/K$_{3}$ intensity ratio shows peaks at 60°N, 0° and 60°S. Slope profiles show spectral response to magnetic activity peaks near K$_{3}$ with north-south asymmetries. Such variations in the line profiles are important in the studies of solar irradiance, surface flux transport and solar dynamo. |
| title | Variations of the Ca II K Line Profile Parameters with Solar Latitude and Time Observed from Kodaikanal Solar Observatory |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2507.14609 |