Abstract:
The network structure seen in the solar images is the outline of supergranulation, which is the large-scale
convection in the Sun with a size of about 30 Mm and a lifetime of 24 hr. We have obtained the supergranulation
lane widths from the autocorrelation function of image windows from the Ca II K spectroheliograms. The images
are obtained from the 100 yr Kodaikanal data, which contains information on more than nine solar cycles. The lane
widths are known to show a positive correlation with the sunspot number. It is now found that the lane widths,
obtained near the mid-latitudes during the sunspot cycle minima, are strongly correlated to the following sunspot
number maxima. A straight-line fit adequately describes the variation. It is also found that the correlation is weak
or insignificant at other times. The strong correlation of the two parameters thus provides a simple way to predict
the maximum sunspot number about 4–5 yr in advance. The results are important in space weather predictions and
solar irradiance variations.
