Numerical solutions from linear theory and QL approach: Growth rates ($\stackrel{\sim }{\gamma }$) of the RH-PB instability (top) and the corresponding time evolutions for the wave energy density (second row), beam velocity (third row), and the beam temperature anisotropy (bottom) for different initial conditions: v_b/v_Ac = 3.0, 2.5, 2.0 (left column), n_b/n_p = 0.06, 0.03, 0.01 (second column), β_c∥ = 1.0, 0.41, 0.1 (third column), and A_b = 2.0, 1.0, 0.62 (right column). The red dots and dashed and dotted lines are explained in the text.