Current Collection by a High-Voltage Sphere from a Cold Magnetoplasma
Technical rept. no. 6, Feb-Dec 87,
S-CUBED LA JOLLA CA
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We consider a high-voltage spherical probe with parameters representative of the SPEAR I rocket experiment in the ionospheric plasma. Computer simulations using particle-tracking and Poisson solution illustrate the compression of the sheath in the direction normal to the magnetic field, the nature of the particle trajectories, and the space charge structure in the sheath. It is found that for a cold, dense plasma, the sheath is nearly confined within the Parker-Murphy radius and the collected current is near the Parker-Murphy limit. If the plasma is warmer and less done, the sheath expands beyond the Parker-Murphy radius and the collected current decreases. In addition, we present a modified orbit-limited theory capable of reproducing many of the qualitative and quantitative features of the sheath structure without the need for particle-tracking.
- Plasma Physics and Magnetohydrodynamics