Visibility of Jupiter's Red Spot

Abstract

THE existence of a relationship between the visibility (V) of Jupiter's red spot and the Zurich relative sunspot number (RZ) was claimed in a letter by Graf, Smith and McDevitt1. Subsequently it was shown by Argyle2 that the correlation coefficient between V and RZ was too low (r = 0.27) to support the hypothesis put forward by Graf et al. The correlation analysis was then extended to more recent data by Solberg and Chapman3, who found an even lower value for r. In a recent letter Basu4 has attempted to reinstate the original claim of Graf et al. by smoothing and partitioning the data before performing the correlation analysis. Basu states that the smoothed visibility function for Jupiter's red spot in the selected period 1894–1945 was dependent on solar activity, but that this dependence vanished or changed about 1947, and had not returned by 1965.