Evolution of key parameters as functions of the planet separation. Top panel: Planet velocity components, including the planet speed (|v|), (negative) radial velocity (−v_r), and azimuthal velocity (v_ϕ). For comparison, we also show the local Keplerian speed (v_K) and the descent speed (v_sink) given by Equation (3). Bottom panel: Key dimensionless quantities that characterise various processes, including the planet’s Mach number (ℳ), the ratio of planet radius to density scale height (R_p/H), tidal disruption parameter (f_td, Equation (9)), ram-pressure disruption parameter (f_d, Equation (7)), f_d evaluated with the Keplerian speed (f_d, K), and the ratio of the maximum density inside the planet to the background density (ρ_p, max/ρ). The grey region shows the extent of the convective envelope.