The novel physics of relativistic ion cyclotron instabilities is numerically investigated. The growth rate spectrums and the possibility being absolute instability of two fast ion cases (that the fast ions are energetic proton and alpha particle, respectively) are numerically studied and compared with the analytical theory. The fundamental difference in the characteristics of the instabilities due to a slight change in fast ion mass per nucleon is emphasized; it is determined by the relative normalized mass deficit per nucleon of fast and slow ions, and by the difference of their Lorentz factors. For the energetic proton case, both a cubic instability and a high harmonic quadratic instability can be driven; while, for the energetic alpha particle case, only the quadratic instability can occur at the high alpha cyclotron harmonics in the lower hybrid frequency regime and above; the threshold is determined by the dielectric constant of the slow ion. The peak growth rate is highest at the harmonics just over the threshold. Many new physics discovered by the numerical results are explained. A numerical polynomial expansion method with curve fitting is developed to conclude that the instabilities studied are absolute, because the analytical results cannot be used to address this important issue.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics