Adiabatic Electron Fluid in the Presence of Strong Space-Charge Forces

We treat the case of an electron fluid with finite pressure embedded in a slowly varying axial magnetic field. Allowing for the presence of ions and accompanying space-charge forces, we find that variations in the resulting drift velocity vD alter the electron's precession frequency from the gyrofrequency Ω to a new frequency ω, with ω2 = Ω2 - Ω·(▿×vD). The precession orbit becomes distorted into an ellipse and the conventional adiabatic invariant is replaced with a new one. The fluid-dynamic consequences of these alterations are explored in the limit that the initial electron pressure is small compared to the initial magnetic pressure.