Theory of an Electrostatic Probe in a Strong Magnetic Field. II

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Abstract
A probe is considered in a magnetic field so strong as to impair collective transverse drifts. Then the charges supplied to the probe come mainly from a long tube of force, whose radius is about one Larmor radius larger than the probe. Assume that there is acting a diffusion process, more efficient than ordinary drifts, which continuously exchanges particles between the inside of the tube of force and the rest of the plasma. In a previous paper we have proposed a one‐dimensional model of this process, leading to an integro‐differential Poisson's equation, which has now been fully investigated in the case of slow diffusion. The solution consists of a chargeless, slowly decaying potential which describes the geometrical screening effect of the probe; while in the sheath an approximate boundary‐layer solution matches with the probe's potential VP. The asymptotic relation between the current collected and VP is computed. This model may be suited to the case of diffusion due to random wave fields.