The near‐wake structure of the Atmosphere Explorer C (AE‐C) Satellite: A parametric investigation

Abstract

Measurements of ion current, electron temperature, and values of space potential obtained from the cylindrical electrostatic probe on board the Atmosphere Explorer C (AE-C) satellite were used to examine, in a parametric manner, the angular distribution of charge around the satellite. Interest is focused on nighttime equatorial data in the altitude range 275-620 km, which yields a wide range for the parameter RD (=Ro/)ko, where Ro is the radius of the satellite and 3,0 is the ambient value of the Debye lengths), including Ro > 10 •', which is of practical significance to large space platforms. The variations of normalized ion current in the wake zone of the AE-C satellite appear to display an exponential dependence on R o for 'constant' values of other relevant parameters. The angular variations of electron temperature (Te) and space potential (4s) in the close vicinity of the satellite's surface were examined and compared with results from the Explorer 31 satellite. The variation of the ratio 3• = ½s(measured)/ ½•(computed) with Te was examined using data from both the AE-C and the Explorer 31 satellites. Itwas found that 3• > 1. Possible causes for the above inequality are discussed. A. 513 mainly to the well-known difficulties of achieving a self-consistent solution of the Vlasov-Poisson equations for practical boundary conditions and plasma parameters. The available theories differ mathematically in the numerical approaches adopted in order to obtain approximate solutions. More important, the theories often employ physical assumptions whose validity and range of applicability to satellite-ionosphere interaction are subject to controversy. A possible way of gaining a good physical insight into the degree and range for the validity and applicability of the assumptions used in the theoretical models is via theory-experiment comparisons. Such comparisons should be performed using in situ measurements conducted for the widest possible range of plasma parameters. Unfortunately, no such studies have been performed in an extensive and physically meaningful manner, except for the studies of Gurevich et al. [1970], Sarnir and Jew [1972], Gurevich and Dimant [ 1975], and Sarnir et al. [ 1975], which used a relatively small sample of in situ measurements under a restricted range of plasma parameters. A major reason for the latter shortcoming is the meager and limited amount of in situ measurements available at the present time for such studies. More detailed discussions on the state of knowledge are given elsewhere [e.g., Samir, 1973; Samir et al., 1977; Fournier and Pigache, 1975; Gurevich and Pitaevskii, 1975; Liu, 1975; Al'pert, 1976].The wide complement of instruments on the Atmosphere Explorer satellites described in great detail elsewhere (see the special edition of Radio Science on the Atmosphere Explorer satellites, 8(4), 1973) provides an opportunity to study the angular distribution of charged particles around the satellites, where all the relevant plasma parameters are known. Such an opportunity did not always...

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

“…for RD • 10-102 [Samir et al, 1979 In this paper we examine some recent results obtained from low-energy particle probes mounted on the Orbiter Columbia during the STS 3 mission and compare them with results from small ionospheric satellites. Of specific interest will be the comparison of interaction characteristics such as…”

“…However, such errors are relatively small and definitely much smaller than an order of magnitude. This was discussed in the works bySamir et al [ 1979. The Sarnir et al[ 1980] study was concerned with ions and not with electrons and, as is known, the electron flux differs significantly from the ion flux in the maximum wake position[S amir et al, 1973], as shown inFigure 6.…”

“…It should be noted that both the results from the STS 3 experiment and the experiments from the small scientific satellites yield values 'for c• that are larger than those predicted by most theoretical models based on the "neutral approximation" [see Samir and Willmore, 1965, Gurevich et al, 1969, Samir et al, 1973, Al'pert, 1983].From the available theoretical models it is not yet possible to predict realistic, quantitative values for c• for conditions relevant to the SRPA-SLP experiment on the STS 3. The same is true for the results from small satellites at perigee altitudes, although more data are available there and more parametric studies have been performed [e.g.,Al'pert, 1983;Parker, 1976Parker, , 1983Samir et al, 1979]. From empirical analyses of the data from small satellites (e.g., Explorer 31 and AE-C), c• was found to vary by about an order of magnitude when RD ranged from 37 to 247[S amir et al, 1980].…”

Charge transfer by high-energy electrons onto the leeward surfaces of a solid in a supersonic rarefied plasma flow

“…A dielectric coating was applied to one side of the plate made of aluminum (length l = 45 cm, width 2R = 16 cm, and thickness δ ≈ 0.1 cm). An aluminum coating was applied (sprayed) onto the surface of the disk (made of quartz) 15 [4] for Sei ≈ 8, R ds ≈ 40, and −Φw ≈ 0 (5) and 20 (6); points 7-9 are the results measured in [12] in the ionosphere on the Explorer-C (AE-C) artificial satellite for 5.9 Sei 8.04, −Φw ≈ 10, and R ds ≈ 116.3 (7), 135.7 (8), and 162.5 (9); points 10 are the results measured in [13] in the ionosphere on the S3-2 artificial satellite for Sei ≈ 8, R ds 45, and −Φw ≈ 10; points 11 are the results measured in [14] in the wake behind the Space Shuttle for Sei ≈ 3.35 and R ds 2 · 10 3 ; (b) angular distribution of ion density nis(θ) at t = 0.192: points 1 are the results measured in [12] on the Explorer-C (AE-C) artificial satellite for Sei ≈ 7.83, R ds ≈ 73.4, −Φw ≈ 8.8, and ξei = 1.14; points 2 are the results measured in the present work (wake behind a cylinder for Sei ≈ 5.1, R ds ≈ 78, −Φw ≈ 6.7, and ξei = 4); curve 3 is the solution of Eq. (7) with the dependence nis(Φ) from [6] for Sei ≈ 5.1, R ds ≈ 80, and −Φw ≈ 6.7; points 4 are the results of the discrete flow model [11].…”

The spherical segmented Langmuir probe in a flowing thermal plasma: numerical model of the current collection

“…Singh et al (1987) and Samir et al (2001) demonstrated that the electrons and ions are heated in the wake, while Siskind et al (1984) also observed an electron heating in the ram direction. Henderson and Samir (1967) measured the current depletion in the wake with respect to the ram and Samir et al (1979 studied the asymmetry in the current distribution in the wake. Oran et al (1974) observed the increasing of the density in the near-wake region.…”