Variations of solar indices during the sunspot maximum years (1999-2002) of cycle 23

Abstract

Comparison of the evolutions of daily and monthly values of several solar indices during 1999-2002 indicated that the daily values had large day-to-day fluctuations with peak spacings differing considerably from the 27-day solar rotation period. Plots of the percentage increases (trough-to-peak) versus temperature of the source regions of the various indices indicated a double-humped structure. The monthly values showed many peaks. The average spacing was -3.5 months (-100 days). The 12-month moving averages showed considerable differences. Some indices reached a maximum near March

2000. Some of these decreased since then and continue to decrease at present; but some reached a minimum near January 2001 and remained steady there, or started increasing again to reach a probable maximum near June 2002. Some indices did not have a maximum in March 2000 and continued to increase till June 2002. Thus, the evolutions of the various solar indices during the sunspot maximum of cycle 23 (1999-2002) are substantially different from each other. Obviously, the dynamical upheavals in the photosphere reach upper levels of the solar atmosphere with varying intensities.