The discover of Ultra High Energy Neutrino of astrophysical nature may be already reached .
Indeed upward and horizontal \tau Air-showers emerging from the Earth crust or mountain chains offer the best and most powerful signal of Ultra High Energy UHE neutrinos \nu _ { \tau } , \bar { \nu } _ { \tau } and \bar { \nu } _ { e } at PeV and higher energy .
The multiplicity in \tau Air-showers secondary particles , N _ { opt } \simeq 10 ^ { 12 } ( E _ { \tau } / PeV ) , N _ { \gamma } ( < E _ { \gamma } > \sim 10 MeV ) \simeq 10 ^ { 8 } ( E _ { \tau } / PeV ) , N _ { e ^ { - } e ^ { + } } \simeq 2 \cdot 10 ^ { 7 } ( E _ { \tau } / PeV ) , N _ { \mu } \simeq 3 \cdot 10 ^ { 5 } ( E _ { \tau } / PeV ) ^ { 0.85 } make easy its discover .
UHE \nu _ { \tau } , \nu _ { \tau } following Super Kamiokande evidence of neutrino flavour mixing , ( \nu _ { \mu } \leftrightarrow \nu _ { \tau } ) , should be as abundant as \nu _ { \mu } , \bar { \nu } _ { \mu } .
Also anti-neutrino electrons , \bar { \nu } _ { e } , near the Glashow W resonance peak , E _ { \bar { \nu _ { e } } } = M ^ { 2 } _ { W } / 2 m _ { e } \simeq 6.3 \c { 1 } 0 ^ { 15 } eV , may generate \tau Air-showers .
Such horizontal \tau air-showers by \nu _ { \tau } N and UHE \bar { \nu } _ { e } e at PeV emerging from mountain high chain might be the most power-full UHE neutrino 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 Cherenkov lights toward detectors located on the top of the mountain or balloons .
Such upward \tau air-shower may hit also nearby satellite flashing them by short , hard , diluted \gamma - burst at the edge of Gamma Ray Observatory BATSE threshold .
We identify already these rarest gamma events with recent ( 1994 ) discovered upward Terrestrial Gamma Flashes ( TGF ) ; we show their very probable UHE \tau -UHE \nu _ { \tau } origin .
Partial TGF Galactic signature and known galactic and extra-galactic source location are discovered within known 47 TGF events at low , { \simeq 2 \cdot 10 ^ { -3 } } probability threshold .