electron neutrinos to be ~34% of the total neutrino flux (the electron neutrino flux measured via the charged current reaction, and the total flux via the neutral current reaction). The SNO results agree well with the expectations. Earlier, Kamiokande and Super-Kamiokande measured a mixture of charged current and neutral current reactions, that also support the occurrence of the MSW effect with a similar suppression, but with less confidence. For the low-energy solar neutrinos, on the other hand, the matter effect is negligible, and the formalism of oscillations in vacuum is valid. The size of the source (i.e. the solar core) is significantly larger than the oscillation length, therefore, averaging over the oscillation factor, one obtains . For = 34° this corresponds to a survival probability of Pee ≈ 60%. This is consistent with the experimental observations of low energy solar neutrinos by the Homestake experiment (the first experiment to reveal the solar neutrino problem), followed by GALLEX, GNO, and SAGE (collectively, gallium radiochemical experiments), and, more recently, the Borexino experiment, which observed the neutrinos from pp (< 420 keV), 7Be (862 keV), pep (1.44 MeV), and 8B (< 15 MeV) separately. The measurements of Borexino alone verify the MSW pattern; however all these experiments are consistent with each other and provide us strong evidence of the MSW effect. These results are further supported by the reactor experiment KamLAND, that is uniquely able to measure the parameters of oscillation that are also consistent with all other measurements. The transition between the low energy regime (the MSW effect is negligible) and the high energy regime (the oscillation probability is determined by matter effects) lies in the region of about 2 MeV for the solar neutrinos. The MSW effect can also modify neutrino oscillations in the Earth, and future search for new oscillations and/or leptonic CP violation may make use of this property. Supernova neutrinos and the MSW effect Supernovae are calculated to emit of the order of neutrinos and antineutrinos of all flavors, and supernova neutrinos carry away about 99% of the gravitational energy of the supernova and are considered strongest source of cosmic neutrinos in the MeV range. As such, scientists have attempted to simulate and mathematically characterize the action of MSW dynamics on SN neutrinos. Some effect of MSW flavor conversion has already been observed in SN 1987A. In the case of normal neutrino mass hierarchy, and , transitions occurred