Here adiabatic and hydrodynamical models for the behavior of a plasma are distinguished. Their distinction lies primarily in the treatment of electron responses, parallel dynamics, and collisionality.
Adiabatic Model
Adiabatic or colisionless electrons respond nearly instantaneously along magnetic field lines. Their parallel motion maintains the Boltzmann Relation. They propagate with small damping and are dominated by density and temperature gradients.
Approaches often simplify to linearized
Hydrodynamic Model
Electron motion along the field lines includes resistive and collisional effects. The electron density doesn’t always follow a Boltzmann relation. Explains drift-wave growth as phase shifts between density and potential can be simulated.