A search for 5-min oscillation in total microwave flux of the sun observed at Toyokawa

A search for 5-min oscillation was performed using the data of solar total flux at four different microwave frequencies taken in the period August, 1977 through July, 1978 on the full automatic polarimeters at Toyokawa, Japan. Spectral analysis of about 600 hours of data showed that there are no periodic components with statistical significance (more than 95% confidence) in the fluctuation of the flux. Upper limits of the oscillating amplitude at the period of 300 sec are 2.7, 5.1, 13, and 53 K at 9.4, 3.75, 2.0, and 1.0 GHz respectively. Correlations between the parameters of fluctuating power of total flux and solar activity were also investigated. When solar activity is very high, spectral power increases particularly at lower frequency range (1 - 5 mHz).