Theory of electrostatic probes in a low-density flowing continuum plasma: numerical solutions for a sphere stagnation point

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Abstract
An exact numerical method has been used to study a probe stagnation point in a continuum flowing plasma. The solutions for the 'low-density continuum' plasma, i.e. with mean free path<c from 0 to 10, and scaled probe potentials phi p/ epsilon from 0 to +or-32, where phi p=eVp/kTe, epsilon =T/Te. The numerical results show that (i) the usual semi-log method for temperature determination leads to large errors; (ii) the effect of flow leads to large errors in the space potential determination; (iii) for a sufficiently large accelerating potential, the currents always show a linear dependence; (iv) approximate current expressions are suggested at smaller Reynolds numbers (Rec<or=1).