Detecting Solar Neutrino Flare in Megaton and km³ detectors

To foresee a solar flare neutrino signal we infer its upper and lower bound. The upper bound was derived since a few years by general energy equipartition arguments on observed solar particle flare. The lower bound, the most compelling one for any guarantee neutrino signal, is derived by most recent records of hard Gamma bump due to solar flare on January 2005 (by neutral pion decay).The observed gamma flux reflects into a corresponding one for the neutrinos, almost one to one. Therefore we obtain minimal bounds already at the edge of present but quite within near future Megaton neutrino detectors. Such detectors are considered mostly to reveal cosmic supernova background or rare Local Group (few Mpc) Supernovas events. However Megaton or even inner ten Megaton Ice Cube detector at ten GeV threshold may also reveal traces of solar neutrino in hardest energy of solar flares. Icecube, marginally, too. Solar neutrino flavors may shine light on neutrino mixing angles.