Linear growth rate of the RTI for a fully ionized plasma (ideal MHD) as a function of the Alfvén speed . In the upper panel curves, different values of the propagation angle θ are shown for a fixed value of β = 0.1, while different β are plotted for a fixed value of θ = 40° in the lower panel curves. In all the panels, the values ρ₂/ρ₁ = 100, g = 270 m s^-2, and k = 10^-7 m^-1 have been used. The dashed curves correspond to the incompressible MHD limit in Eq. (1).