Gravitational tidal waves in Titanʹs upper atmosphere

Tidal waves driven by Titanʹs orbital eccentricity through the time-dependent component of Saturnʹs gravitational potential attain nonlinear, saturation amplitudes ( | T ′ | > 10   K , | u ′ | > 20   m s −1 , and | w ′ | > 5   cm s −1 ) in the upper atmosphere (⩾500 km) due to the approximate exponential growth as the inverse square root of pressure. The gravitational tides, with vertical wavelengths of ∼100–150 km above 500 km altitude, carry energy fluxes sufficient in magnitude to affect the energy balance of the upper atmosphere with heating rates ⩾ 10 −9   erg cm −3 s −1 in the altitude range of 500–900 km.