Ultra High Energy ( UHE ) Cosmic Rays , UHECR , may graze high altitude atmosphere leading to horizontal upward air-showers .
Also PeVs \bar { { \nu _ { e } } } hitting electron in atmosphere may air-shower at W ^ { - } boson resonant mass .
On the other side ultra high energy muon and electron neutrinos may also lead , by UHE neutrinos mass state mixing , to the rise of a corresponding UHE Tau neutrino flavor ; the consequent UHE tau neutrinos , via charge current interactions in matter , may create UHE taus at horizons ( Earth skimming neutrinos or Hor-taus ) whose escape in atmosphere and whose consequent decay in flight , may be later amplified by upward showering on terrestrial , planetary atmospheres .
Indeed because of the finite terrestrial radius R _ { \oplus } , its thin atmosphere size ( h _ { 0 } \simeq 10 ) km , its dense crust , the UHE tau can not extend much more than \sim \sqrt { R _ { \oplus } h _ { 0 } \pi / 2 } \simeq 360 kilometers in air , corresponding to an energy E _ { \tau \oplus } \simeq 7.2 EeV , near but below GZK cut-off ones ; on the contrary Jupiter ( or even Saturn ) may offer a wider , less dense and thicker gaseous layer at the horizons where Tau may loose little energy , travel longer before decay and rise and shower at E _ { \nu _ { \tau } } \simeq 4 - 6 \cdot 10 ^ { 19 } eV or ZeV extreme energy .
Also solar atmosphere may play a role , but unfortunately tau-showers secondaries maybe are too noisy to be disentangled , while Jupiter atmosphere , or better , Saturn one , may offer a clearer imprint for GZK ( and higher Z-Burst ) Tau showering , well below the horizons edges .