  We have used both the Date-Compensated Discrete Fourier Transform and
Periodogram analysis of the monthly solar neutrino flux data from (1) SAGE
detector during the period from 1st January 1990 to 31st December 2000; (2)
SAGE detector during the period from April 1998 to December 2001; (3) GALLEX
detector during the period from May 1991 to January 1997; (4) GNO detector
during the period from May 1998 to December 2001; (5) GALLEX-GNO detector
(Combined data) from May 1991 to December 2001 and (6) average of the data from
GNO and SAGE detectors during the period from May 1998 to December 2001. (1)
exhibits periodicity around 19, 24 and 80-85 months. (2) shows periodicity
around 1.5 months. For (3) we observe periodicity around 1.6, 2.5 and 19
months. For (4) periodicity is seen around 1.4 and 3.4 months. (5) gives
periodicity around 1.7 and 19 months while (6) shows periodicity around 1.8 and
2.2 months. We have found almost similar periods in the solar flares, sunspot
data, solar proton data which indicates that the solar activity cycle is due to
the pulsating character of nuclear energy generation inside the sun.
