Divergent migration of two planets resulting from surface density values Σ₀ = 400, 800, 1200 g cm⁻² and viscosity α = 0.01 (top panel). In the middle panel the evolution of the outer planet is shown for the cases with Σ₀ = 400 and 800 g cm⁻², as indicated. In both cases, after an initial phase of inward migration, the planet drifts outward (but the longer-term behavior was not investigated). In the bottom panel the divergent migration is instead due to the outer planet slowing down. In all cases, the inner planet keeps migrating inward.