Laboratory observations of electron temperature in the wake of a sphere in a streaming plasma

Abstract

A parametric study was performed of electron temperature variation in the wake of a conducting sphere in a streaming plasma. The flow conditions were varied as follows: the ambient electron temperatures in the range 850-2450 K; the ambient electron densities in the range 5 x lo'-7 x 106/crn*; and body potentials relative to plasma potential in the range of + 1.7 to-2.8 V for an ion beam energy of-4 eV. Electron temperature enhancements were observed which ranged up to 200 per cent above ambient in the nearest proximity of the body surface. The magnitude of the enhancement depends upon the ambient dennty, temperature and body potential.

On plasma disturbances caused by the motion of the space shuttle and small satellites: A comparison of in situ observations

“…The results of Oran et al [1975], as depicted in Figure 9, are in agreement with the above in situ results; namely, they show an enhancement in Te(wake). The laboratory studies of Oran et al [ 1975] and Stone [1981a] extend the spatial range of measurement and carry them to further distances downstream than the in situ measurements.…”

“…The results of Oran et al [1975], as depicted in Figure 9, are in agreement with the above in situ results; namely, they show an enhancement in Te(wake). The laboratory studies of Oran et al [ 1975] and Stone [1981a] extend the spatial range of measurement and carry them to further distances downstream than the in situ measurements. They show that at about Z = S. R o distance downstream in the wake region, no such enhancement is obvious; hence concuring with, and extending, the Henderson and Samir [ 1967] result, no Te(wake) enhancement is observed at or beyond Z • S R o.…”

“…The electron temperature in the wake behind a body immersed in a synthetic streaming plasma was studied in plasma chambers by Oran et al [1975] and Illiano and Storey [ 1974], and more recently by Intriligator and Steele [1985]. The results of Oran et al [1975], as depicted in Figure 9, are in agreement with the above in situ results; namely, they show an enhancement in Te(wake).…”

“…The authors are aware of the possibility that the electron distribution in the wake may not be truly represented by a Maxwellian, and hence the use of the term "temperature" in the conventional sense may not be justified. However, no such deviations were reported in the examination of the slopes of the current voltage characteristics in the laboratory measurements of Oran et al [1975] and in the Ariel I, Wrenn, 1972;Troy et al, 1975;Medved, 1969;Troy et al, 1970]. Despite this, however, it is possible to argue that when the probes are in the plasma near wake void region, the currents are drastically reduced and the sensitivity limit of amplifiers can be encountered, resulting in fewer data points available for temperature determinations.…”

“…In the present investigation, we will compare the results from the above measurements on the STS 3 Columbia spacecraft with the results (1) obtained from similar measurements made on the Ariel I, Explorer 31, Atmospheric Explorer C (AE-C), and Gemini-Agena 10 satellites [e.g., Samir and Willmore, 1965;Henderson and Samir, 1967;Samir andWrenn, 1969, 1972;Samir et al, 1979;Medved, 1969], and (2) those obtained from laboratory plasma experiments carried out in simulated ionospheric plasmas [e.g., Oran et al, 1975;Stone, 1981a, b, c]. We note that the STS 3 VCAP measurement techniques are similar to those used on the above ionospheric satellites.…”