  Future neutrino detector at Megaton mass might enlarge the neutrino telescope
thresholds revealing cosmic supernova background and largest solar flares
neutrino. Indeed the solar energetic flare particles while scattering among
themselves on Solar corona atmosphere must produce prompt charged pions, whose
chain decays are source of solar (electron-muon) neutrino "flare" (at tens or
hundreds MeV energy). These brief (minutes) neutrino "burst" at largest flare
peak may overcome by three to five order of magnitude the steady atmospheric
neutrino noise on the Earth, possibly leading to their detection above
detection. Moreover the birth of anti-neutrinos at a few tens MeVs is well
loudly flaring above a null thermal "hep" anti-neutrino solar background and
also above a tiny supernova relic and atmospheric noise. The largest prompt
solar anti-neutrino "burst" may be well detected in future SuperKamikande
(Gadolinium implemented) by anti-neutrino signatures mostly in inverse Beta
decay. Our estimate for the recent and exceptional October - November 2003
solar flares and January 20th 2005 exceptional eruption might lead to a few
events above or near unity for existing Super-Kamiokande and above unity for
Megaton detectors. The neutrino spectra may reflect in a subtle way the
neutrino flavor oscillations and mixing in flight. A comparison of the solar
neutrino flare (at their birth place on Sun and after oscillation on the
arrival on the Earth) with other neutrino foreground is estimated: it offers an
independent track to disentangle the neutrino flavor puzzles and its most
secret mixing angles. The sharpest noise-free anti-neutrino imprint maybe its
first clean voice.
