Stability of Alfvén ion-cyclotron modes with finite perpendicular wavenumber

The general dispersion relation for the Alfvén ion-cyclotron (AIC) modes with finite perpendicular wavelength k⊥ and a two-temperature Dory–Guest–Harris (DGH) [Phys. Rev. Lett. 14, 131 (1965)] ion distribution function is solved numerically. Conventional AIC instability is recovered in the limit k⊥ =0. It is shown that as k⊥ increases, the AIC instability smoothly goes over to the electrostatic loss cone instability. Instabilities at second and higher harmonics are excited at finite k⊥ .