Is the neutrino flux from the sun constant? A review

The Homestake radiochemical solar neutrino experiment has been observing the Sun's neutrino flux from 1970 to the present time. The experiment observes the production of 37Ar by the neutrino capture reaction 37Cl (v, e-) 37Ar in 615 metric tons of tetrachloroethylene. The authors and others have reported that the 37Ar production rate anti-correlates with the solar activity cycle. The results of measurements through 1993 are given and compared with various solar phenomena. A short exposure was made during the large-scale solar mass-loss event of June 4, 1991 that resulted in an enhancement of the 37Ar production rate six times greater than the average value. The significance of this event is discussed