The Effect of Wave Fields on Energetic Particles

Abstract

In Chapter 6 we have seen how wave growth and decay is dominated by the behavior of the particle distribution function near the velocity, υ_|| = (ω − l Ω)/k_||. Integrals over velocity space occurring in the expressions for the conductivity or the dispersion relation have poles at this velocity; the residue at this pole determines the imaginary part of the frequency or growth rate. The physics of this situation is that the particles near this velocity remain approximately in phase with the wave as it is propagated. They can thus exchange energy efficiently with the wave. This can lead to growth or decay depending on the relative proportions of the particles which transfer energy to the wave and which gain energy from the wave.