ROTATIONAL MODULATION OF MICROWAVE SOLAR FLUX

Time series data of 10.7 cm solar flux for one solar cycle (1985-1995 years) was processed through autocorrelation. Rotation modulation with varying persistence and period was quite evident. The persistence of modulation seems to have no relation with sunspot numbers. The persist ence of modulation is more noticeable during 1985-1986, 1989-1990, and 1990-1991. In other years the modulation is seen, but its persistence is less. The sidereal rotation period varies from 24.07 days to 26.44 days with no systematic relation with sunspot numbers. The results in dicate that the solar corona rotates slightly faster than photospheric features. The solar flux was split into two parts, i.e., background e mission which remains unaffected by solar rotation and the localized e mission which produces the observed rotational modulation. Both these parts show a direct relation with the sunspot numbers. The magnitude o f localized emission almost diminishes during the period of low sunspo t number, whereas background emission remains at a 33% level even when almost no sunspots may be present. The localized regions appear to sh ift on the solar surface in heliolongitudes.