Planetary gyroscopic waves in Thomson-Delaney cells of the ocean of Jupiter’s moon Europa

Abstract

Observational data of the Galileo mission testify that there is a possibility of existence of planetary waves in the ocean of Jupiter’s moon Europa. A model of rotating ocean is used for the analysis of dynamics of underlying wavy processes. The model uses geometrical stratification of the ocean’s icy surface into separate cells with a typical size of order of 100 km. These cells of hydrothermal nature contain liquid lenses, and the possibility of their origination was postulated and theoretically studied by P. Thomson and J. Delaney in 2001. Using the Bubnov-Galerkin method, the spectrum of natural vibrations of liquid (gyroscopic waves) in Thomson-Delaney cells was found taking into account the satellite’s rotation in a simple model of the icy crust. In order to study a possibility of resonance excitation of tidal oscillations of liquid in the cells, the dominant elements of this spectrum are compared to theoretical values of the frequencies of tide-generating forces associated with eccentricity of the orbit of the Jupiter’s moon Europa and with perturbations from other Galilean satellites of Jupiter. This allows one to discover a large number of resonances on dominant modes with periods of from 3.5 to 7 days in the Europa ocean regions, corresponding to latitudes from 30° to 70°.