Under an applied electric field ions are accelerated parallel to the electric field and electrons
accelerated antiparallel to it. The resulting current vector is proportional and parallel to the electric
field vector - Ohm's law. The proportionality constant - the conductivity - depends on a
balance of the electrostatic force and the drag force, i.e., the rate at which ions and
electrons are decelerated by collision. Generally, the ion-neutral collision frequency is dominant.
In addition, an applied electrostatic force causes the particles to drift together in the direction perpendicular to the electric and magnetic fields - the E x B drift. As the particles drift, collisions inhibit this drift. Since the ions collide with neutrals more often than do the electrons, the ions drift more slowly than electrons. Thus the electrostatic field drives a differential motion between ions and electrons not only in the direction of the electric field but also at right angles to it. We refer to the former as the Pedersen current and the latter as the Hall current. Note that the Hall current flows anti-parallel to the E x B drift.
|BAS Homepage||UASD Homepage||Navigator|