Collisionless plasma flow over a conducting sphere

Stone, N. H.; Oran, W. A.; Samir, Uri

doi:10.1016/0032-0633(72)90201-2

Cited by 16 publications

(6 citation statements)

References 6 publications

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“…The axial ion enhancement just downstream of a body in a plasma flow has been observed previously (Stone, Oran & Samir 1972;Stone 1981a, b) and has usually been attributed to electrostatic focusing of ion streams onto the wake axis (Martin 1974;Taylor 1967). A detailed review is given in the thesis of Stone (1979).…”

Section: Introductionmentioning

confidence: 90%

The interaction of a conducting object with a supersonic plasma flow: ion deflection near a negatively charged obstacle

Merlino

D’Angelo

1987

J. Plasma Phys.

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An experimental study of the interaction of a conducting object with a flowing plasma is described. Particular attention is given to the deflection of ions in the sheath of a negatively charged body. The experiments were conducted in a double plasma device in which a relatively weak longitudinal magnetic field may also be present. For the particular conditions used in these experiments, it was found that ion deflection occurs primarily near the edge of the body. A simple physical model is discussed which accounts for the observed dependences of the convergence of ion streams on the body potential and ion beam velocity. A density rarefaction wave is also observed in the wake region, which propagates into the ambient plasma at roughly the ion acoustic Mach angle. Finally, some preliminary observations of the spatial distribution of plasma noise in the wake region are presented.

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Section: Introductionmentioning

confidence: 90%

The interaction of a conducting object with a supersonic plasma flow: ion deflection near a negatively charged obstacle

Merlino

D’Angelo

1987

J. Plasma Phys.

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“…The gas throughput has been matched to the pumping system so that operational residual gas pressures in the vacuum chamber are maintained in the range 10~6 to 10~7 torr. This is a sufficiently low pressure to reduce slow, charge-exchange ions to a negligible level (see Oran, Samir & Stone 1976;Stone 1979).…”

Section: Experimental Apparatus and Conditionsmentioning

confidence: 99%

“…For convenience, we define the region behind the test body where the ion density is reduced as the near-wake region, the region where a single axial ion current peak occurs as the mid-wake region, and the region where the axial peak divides and beyond as the far-wake region. This particular set of data was first presented in Stone et al (1972). Here, these data, together with several other data sets from case I but with differing values of <i> 6 , are analyzed in more detail and in the context of recently obtained ion flux vector measurements (case II in table 1).…”

Section: Case I Datamentioning

confidence: 99%

“…However, it can be concluded from the results of laboratory investigations by Bogashchenko et al (1971) and Astrelin et al (1973) that imbedded magnetic fields similar in strength to the geomagnetic field are of secondary importance when studying charged-particle distributions in the near vicinity of bodies which are of the order of a few tens of Debye lengths in size (Stone 1979). Fournier & Pigache (1975) have studied the effects of thermal ion motion, and their findings have been used to estimate how ion thermal motions typical of the ionospheric plasma may be expected to affect laboratory results (Stone 1979). The conclusion reached is that the effects discussed herein may be diffused and reduced in amplitude but should still occur under some conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The focusing of ion streams onto the wake axis by electric fields in the plasma sheath surrounding conducting test bodies has long been inferred from the presence of axial current peaks or diverging wave-like structures in the mid-and far-wake regions (e.g. Clayden 1963;Hall, Kemp & Sellen 1964;Clayden & Hurdle 1966;Hester & Sonin 1969a, b, 1970Stone, Oran & Samir 1972;Stone, Samir & Oran 1974;Fournier & Pigache 1975), and has been predicted by several theoretical treatments (e.g. Davis & Harris 1961;Maslennikov & Sigov 1965, 1967, 1969Maslennikov, Sigov & Charkina 1968;Taylor 1967;Call 1969;Martin 1974).…”

Section: Introductionmentioning

confidence: 99%

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The plasma wake of mesosonic conducting bodies. Part 1. An experimental parametric study of ion focusing by the plasma sheath

Stone

1981

J. Plasma Phys.

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An experimental, parametric investigation has been made of the disturbed ion flow field immediately downstream from conducting bodies of spherical and long cylindrical geometries in a collisionless, mesosonic plasma stream. The ion-acoustic Mach number, S, and the normalized test body potential, Φb, were varied, while the test body radii were of the order of a Debye length for all cases. In addition to standard diagnostics, the ion flux intensity, energy and direction were measured with the recently developed differential ion flux probe. These vector measurements provide direct observations of ion streamlines deflected across the wake axis at an angle proportional to sin-1 (|Φb|½/S) and show that some deflected streamlines are bunched together to form converging ion beams which can exist in the near wakes of both test body configurations. The angle of inclination of the converging ion beams depends linerarly on Φb, while the position of their intercept on the wake axis varies with S|Φb|½. The vector flux measurements also provide direct observations of secondary ion trajectory deflexions in the mid-wake region. These features exhibit parametric dependences that are in good agreement with theoretical calculations that include the effects of the test body and space charge potentials.

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Does a ?two-stream? flow model apply to wakes of large bodies in space?

Samir

Stone

Oran

1974

Astrophys Space Sci

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Structural patterns of ion and electron currents observed on the wake axes of the Ariel I and the Gemini I0 space vehicles are re-examined, together with relevant theoretical and laboratory 'simulation' studies. Some insight into existing in-situ data is provided. The possibility that 'converging-stream" models describe structural features of current enhancements in the wake region of large spacecraft is discussed.The only available axial profiles of charged particle currents in the wake of a large spacecraft were presented by Troy et al. (1970), based on the wake experiment of the Gemini/Agena 10 spacecraft system. The probes mounted on the Agena vehicle measured both the ion and electron currents in the wake created by the Gemini as the two vehicles moved apart after an undocking manceuver. These data (which consisted of a single profile each for ion and electron currents) are shown in Figure 1. The spacecraft configuration is shown in Figure 2a. At about 400 km altitude, where the above profiles were measured, the ratio (Rc/2D) is of the order of 100, where Ra is the 'effective' body radius for the Gemini and 2D is the Debye length. The irregularity in (Ie/Ieo) at (r/RG)~6.5 (see Figure 1) may point toward the existence of a slight enhancement in electron current, although it may also be due to spread in the data. It is felt that one can claim that no obvious enhancement in ([+/I+o) and (Io/I~o) was definitely observed in this experiment. Henderson and Samir (1967) presented results for the electron distribution in the wake of the Ariel I satellite at a distance of (r/RA)= 5 downstream from the center of the satellite, where RA ~ radius of the Ariel I satellite. The observations are for satellite perigee altitudes; i.e., 400 to 600 km. A clear enhancement in the electron current was observed in the wake, although the enhancement did not rise above ambient (see Figure 3a). They also reported that a similar electron current enhancement was observed in the wake of the spherical ion probe that inadvertently served as a

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Collisionless plasma flow over a conducting sphere

Cited by 16 publications

References 6 publications

The interaction of a conducting object with a supersonic plasma flow: ion deflection near a negatively charged obstacle

The interaction of a conducting object with a supersonic plasma flow: ion deflection near a negatively charged obstacle

The plasma wake of mesosonic conducting bodies. Part 1. An experimental parametric study of ion focusing by the plasma sheath

Does a ?two-stream? flow model apply to wakes of large bodies in space?

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