On the spectral study of sunspot number and solar radio flux between 600 and 9400 MHz

The relationship between the solar activity, as represented by sunspot number and the slowly varying component of solar radio emission at frequencies from 600 to 9400 MHz, has been sudied for high solar activity (1957–58), declining phase of moderate solar activity (1961–62) and ascending phase of moderate solar activity (1965–66). Regression and auto-spectrum analyses show that the association of the slowly varying radio emissions with sunspot activity is best around 3750 MHz for high solar activity period, around 2800 MHz for moderate activity during the declining phase and in between 2800 and 3750 MHz for ascending phase of activity. The coherence between radio flux at frequencies from 600 MHz to 9400 MHz was high and free from large fluctuations upto wavelengths as short as 7 days in the year 1961–62. At 9400 MHz, however, it is high and steady for wavelengths in excess of about 15 days. At solar synodic rotation period the phase difference between the sunspot number and the slowly varying component shows little change with the wavelength of the radio emission.