Origin of tidal dissipation in Jupiter. I. Properties of inertial modes

We study global inertial modes with the purpose of unraveling the role they play in the tidal dissipation process of Jupiter. For spheres of uniformly rotating, neutrally buoyant fluid, we show that the partial differential equation governing inertial modes can be separated into two ordinary differential equations when the density is constant or when the density has a power-law dependence on radius. For more general density dependencies, we show that one can obtain an approximate solution to the inertial modes that is accurate to the second order in wavevector. Frequencies of inertial modes are limited to omega < 2 Omega (Omega is the rotation rate), with modes propagating closer to the rotation axis having higher frequencies. An inertial mode propagates throughout much of the sphere with a relatively constant wavelength and a wave amplitude that scales with density as 1/root p p. It is reflected near the surface at a depth that depends on latitude, with the depth being much shallower near the special latitudes theta cos(-1) omega/2 Omega. Around this region, this mode has the highest wave amplitude as well as the sharpest spatial gradient (the singularity belt''), thereby incurring the strongest turbulent dissipation. Inertial modes naturally cause small Eulerian density perturbations, so they are only weakly coupled to the tidal potential. In a companion paper, we attempt to apply these results to the problem of tidal dissipation in Jupiter.