Comparison of relevant timescales calculated via Eqs. (3) and (4). The dashed line represents the loss timescale through pp channel. The shaded areas represent the diffusion timescale for the interval δ =  [0.3...0.6] . The solid lines are for δ = 0.5. The crossing of the dashed and solid lines represent the minimal energy at which total cloud penetration is fulfilled for a diffusion coefficient of D₁₀ = 10²⁶ cm² s^-1 (black), D₁₀ = 10²⁷ cm² s^-1 (red), D₁₀ = 10²⁸ cm² s^-1 (green).