ABSTRACT
This chapter presents that the quasineutral hybrid models are conceptually fairly simple and powerful. At intermediate time scales, a mixing of the particle-like and the fluid-like behaviors of plasma often emerges. Such phenomena may be best described by a hybrid of the particle method and the fluid approach. A natural example of a hybrid picture of plasma is that of fluid-like electrons and particle-like ions. For low frequency waves in an electrostatic problem, electrons respond to the field almost instantaneously, the ions are thereby shielded and charge separation effects become much reduced. The charge neutrality is, therefore, approximately satisfied. Electrons are adjusting quickly to the charge separation along the field line. Electrons under the present condition adjust to the electric field along the field line so quickly that they behave adiabatically. The model was particularly useful for low frequency waves propagating nearly perpendicular to an external field.
