Concepedia

Anomalous Electron Diffusion and Ion Acceleration in a Low-Density Plasma

G. S. Janes, R. S. Lowder

The Physics of Fluids · 1966 · 295 citations · 9 references

Concepts

TL;DR

The study examines ion and electron transport in a weakly turbulent plasma with crossed E and B fields, where the ion gyro radius exceeds apparatus dimensions and a slowly rotating density concentration with superimposed high‑frequency fluctuations is present. The experimental geometry allows quantitative measurement of electron and ion currents. Ions are freely accelerated by electrostatic forces, while electrons exhibit anomalous diffusion across the magnetic field due to E×B drifts from correlated electric field and density fluctuations, with measured currents matching predictions and agreeing with Yoshikawa and Rose’s turbulent diffusion theory.

Abstract

Ion and electron transport properties have been measured in a steady state, weakly turbulent plasma that was subjected to crossed E and B fields. The geometry permits quantitative measurements of electron and ion currents. The ion gyro radius is large compared to the apparatus dimensions. Measurements of the potential gradients, Hall currents, and ion velocity show that the ions are freely accelerated through the plasma by electrostatic forces. However, an ``anomalous diffusion'' of electrons is observed since the electron current across the magnetic field is much too large to be due to collisional diffusion. The plasma is weakly turbulent, consisting of a slowly rotating density concentration on which higher frequency fluctuations are superimposed. Electric field fluctuations are found that are correlated with the density variations so as to produce the ``anomalous diffusion'' via adiabatic E × B drifts. The magnitudes of these electric field and density variations are used to predict a net electron current that agrees with the direct measurements of this current. Reasonable agreement with the turbulent diffusion theory of Yoshikawa and Rose is obtained.

References

9

252 citations

188 citations

Anomalous Diffusion of a Plasma across a Magnetic Field

S. Yoshikawa, David J. Rose · The Physics of Fluids · 1962

+12

120 citations