Which Solar Latitude Follows the Sunspot Cycle Exactly?

Abstract

The large-scale convection in the Sun known as supergranulation is manifested as a network structure on the solar surface. The network cells have an average lifetime of 24 hr, a size of about 30 Mm, and a lane width of about 6 Mm. We have obtained the lane widths and intensities at different latitudes from the Ca {\sc ii} K spectroheliograms from the 100 yr Kodaikanal archival data. We have then calculated the cross correlation function of lane widths and intensities with sunspot number at every latitude from 60${}^{\circ }$ N to 60${}^{\circ }$ S. The correlation coefficients of the quantities show an approximate North-South symmetry with broad peaks around $\pm$(11--22)${}^{\circ }$ latitude with values of about 0.8. The results imply that these latitudes follow the sunspot cycle strongly. The maximum correlation for the lane widths occurs (18$\pm$2)${}^{\circ }$ N and (20$\pm$2)${}^{\circ }$ S with no phase difference. For intensities, this happens at (13$\pm$2)${}^{\circ }$ N and (14$\pm$2)${}^{\circ }$ S with a phase difference of 1.25 to 1.5 yr. It is interesting to note that the lane width correlations peak during the solar maximum whereas the intensitiy correlations peak 1.25--1.5 yr after the solar maximum. The results, generally show that no unique latitude exactly follows the solar cycle for all quantities. The results are important in flux transport on the solar surface and have implications for the quiet Sun UV irradiance variations.

7 pages, 3 figures

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