Oblique ion collection in the drift-approximation: how magnetized Mach-probes really work

I H Hutchinson

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arXiv · 0809.1557

Oblique ion collection in the drift-approximation: how magnetized Mach-probes really work

I H Hutchinson

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Abstract

The anisotropic fluid equations governing a frictionless obliquely-flowing plasma around an essentially arbitrarily shaped three-dimensional ion-absorbing object in a strong magnetic field are solved analytically in the quasi-neutral drift-approximation, neglecting parallel temperature gradients. The effects of transverse displacements traversing the magnetic presheath are also quantified. It is shown that the parallel collection flux density dependence upon external Mach-number is $n_\infty c_s \exp[-1 -(M_{\parallel\infty}- M_\perp\cotθ)]$ where $θ$ is the angle (in the plane of field and drift velocity) of the object-surface to the magnetic-field and $M_{\parallel\infty}$ is the external parallel flow. The perpendicular drift, $\M_\perp$, appearing here consists of the external $\E\wedge\B$ drift plus a weighted sum of the ion and electron electron diamagnetic drifts that depends upon the total angle of the surface to the magnetic field. It is that somewhat counter-intuitive combination that an oblique (transverse) Mach probe experiment measures.

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I H Hutchinson. 2008-10-28. Oblique ion collection in the drift-approximation: how magnetized Mach-probes really work. https://arxiv.org/abs/0809.1557

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