Detecting Ultra High Energy Neutrinos by Upward Tau Airshowers and Gamma Flashes

Tau Air-showers are the best trace of rarest Ultra High Energy neutrinos UHE ${\nu }_{\tau }$, ${\bar{\nu }}_{\tau }$ and ${\bar{\nu }}_e$ at PeV and higher energy. $\tau$ Air-showers may generate billion times amplified signals by their secondaries . Horizontal amplified $\tau$ air-showers by ${\nu }_{\tau }N$ and UHE ${\bar{\nu }}_{e}e$ at PeV emerging from mountain chain might be the most power-full imprint. Upward UHE ${\nu }_{\tau }N$ interaction on Earth crust at horizontal edge and from below, their consequent UHE $\tau$ air-showers beaming toward high mountains should flash $\gamma$,$\mu$,X and optical detectors on the top. Upward $\tau$ air-shower may hit nearby satellite flashing them by short, hard, diluted $\gamma -$burst at the edge of Gamma Ray Observatory BATSE threshold. We identify these events with recent (1994) discovered upward Terrestrial Gamma Flashes (TGF) and we probed their UHE $\tau$ - UHE ${\nu }_{\tau }$ origin. From these TGF data approximated UHE ${\nu }_{\tau }$ flux and $\mathrm{\Delta }{m}_{{\nu }_{\mu }{\nu }_{\tau }}$ sever lower bound are derived. Partial TGF Galactic signature is also manifest within known 47 TGF events clustered within three degrees from the Galactic plane at $\simeq 2\cdot {10}^{-3}$probability. Well known $X-\gamma -\mathrm{T}\mathrm{e}\mathrm{V}$ active galactic and extragalactic sources have found probable counterpart in TGF arrival directions. Detection of elusive UHE ${\nu }_{\tau }$ seem finally achieved.