Maximum growth rate γ_max/Ω_H vs. frequency ω/Ω_H. For each of the three lines the electron anisotropy is constant and the proton anisotropy is varied. The uppermost line with triangles depicts ﹩T^{e}_{\parallel }/ T^{e}_{\perp }=20﹩, the middle line with diamonds ﹩T^{e}_{\parallel }/ T^{e}_{\perp }=15﹩, and the bottom line with asterisks ﹩T^{e}_{\parallel }/ T^{e}_{\perp }=14﹩. The small numbers refer to the corresponding values of ﹩T^{p}_{\parallel }/ T^{p}_{\perp }﹩. The vertical dotted line indicates the ³He⁺² gyrofrequency.