The Fermi Lab Liquid ARgon experiment, FLARE, a huge neutrino argon-liquid project detector of 50 kt mass, might in a near future enlarge the neutrino telescope accuracy revealing in detail solar, supernova, atmospheric as well as largest solar flares neutrino. Indeed the solar energetic (E_p > 100 MeVs) flare particles (protons, alpha) while scattering among themselves or hitting the solar atmosphere must produce on sun prompt charged pions, whose decay (as well as their sequent muon decays) into secondaries is source of a copious solar 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 emergence and detection above the thresholds. The largest prompt "burst" solar neutrino flare may be detected in future FLARE neutrino detectors both in electron and positron and possibly in its muon pair neutrino component. Our estimate for the recent and exceptional October - November 2003 solar flares and last January 20th 2005 exceptional flare might lead to a few events for future FLARE or near unity for present Super-KamiokandeII. The neutrino spectra may reflect the neutrino flavor oscillations and mixing in flight. In neutrino detectors a surprising (correlated) muon appearance may occur while a rarer tau appearance may even marginally take place. A comparison of the solar neutrino flare signal with other neutrino foreground is estimated: it offer the first opportunity for an independent road map to disentangle the neutrino flavor puzzles, as well a prompt alarm system for dangerous solar flare eruptions.