We have to calculate (a) the rate at which the Sun is generating neutrinos. Assume that the energy production is entirely by the proton-proton cycle. (b) We have to find the rate with which the solar neutrinos impinge the Earth.

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(a)

The Sun radiates energy at the rate of . In a p-p cycle there is a fusion of four protons and two electrons to form one alpha particle, two neutrinos and six gamma ray photons. That is the p-p nuclear process is

The energy released in the p-p cycle is 26.7 MeV. Assuming that the energy production is entirely by the proton-proton cycle, we find that the number of such nuclear processes that are taking place in the Sun per second is

As 2 neutrinos are produced per p-p cycle, the rate at which the Sun is generating neutrinos is

(b)

The mean orbital radius of the Earth is , and the mean radius of the Earth is . Therefore, the rate with which the solar neutrinos impinge the Earth is