Intense solar flares originated in sun spots produce high energy particles (protons, α) well observable by satellites and ground-based detectors. The flare onset produces signals in different energy bands (radio, X, gamma and neutrons). The most powerful solar flares as the ones occurred on 23 February 1956, 29 September 1989 and the more recent on October 28th, and the 2nd, 4th, 13th of November 2003 released in sharp times the largest flare energies (EFL≃1031÷1032erg).Thehighenergysolarflareprotonsscatterwithinthesolarcoronaandtheymustbesourceofapromptneutrinoburstthroughtheproductionofchargedpions.Lateron,solarflareparticleshittingtheatmospheremaymarginallyincreasetheatmosphericneutrinoflux.Thepromptsolarneutrinoflaremaybedetectedinthelargestunderground\nudetectors.OurestimatefortheOctober−November2003solarflaresgivesanumberofeventsabovetheunity.Theelectron/muon\nu signals and spectra may reflect the neutrino flavour mixing. A surprising tau appearance may occur for a hard {E}_nu_mu}} \to {E}_{{\nu}_{\tau}}\simeq> 4 GeV) flare spectra.