The initial behavior of high altitude barium releases—II. The expanding vapor cloud

Hoffman, Herbert S.; Best, G. T.

doi:10.1016/0021-9169(74)90226-8

Cited by 4 publications

(1 citation statement)

References 9 publications

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“…Numerous measurements of neutral cloud expansion velocities have been in good agreement and fall within the range 0.9 to 1.2 km/s which Rieger et al [1970] measured for collision-free releases at 2000 kin. An exception has been published by Hoffman and Best [1974], who measured 1.4 ñ 0.2 km/s for the initial (t < 5 s) velocity of a very large release of a slightly different mixture. The theoretical analysis by Draoeatz [1972] predicts a very narrow velocity distribution for the Ba vapor centered on 1.3 km/s for t > 5 s following the conversion of thermal energy to directed kinetic energy and the transition from continuum flow to free molecular flow.…”

Section: Neutral Cloud Expansionmentioning

confidence: 95%

The Cameo Barium Releases: E_∥ fields over the polar cap

Heppner¹,

Miller²,

Pongratz³

et al. 1981

J. Geophys. Res.

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Four successive thermite barium releases at an altitude of 965 km over polar cap invariant latitudes 84° to 76° near magnetic midnight were conducted from the orbiting second stage of the vehicle that launched Nimbus 7. This was the first opportunity to observe the behavior of a conventional barium release when conducted at orbital velocity in the near earth magnetic field and to demonstrate that the μ▽B force at orbital velocity would accelerate the Ba+ ions to much greater altitudes for measuring E∥ fields by observing perturbations in the motion of the visible ions. The principal unexpected characteristic in the release dynamics was the high, 1.4 to 2.6 km/s, initial Ba+ expansion velocity relative to an expected velocity of 0.9 km/s. Characteristics of the neutral gas expansion are also discussed. Under the combined influence of μ▽B and E∥ forces the finely striated Ba+ streamers from the 8 kg releases elongated along the field to dimensions >10,000 km and were photographed from California and Hawaii as well as higher latitude sites. Although observed up to one hour after release and to elevation angles >55° from Southern California, triangulations of upper tips were limited to the initial 25 min and altitudes <23,000 km. The average E⊥ convection of the Ba+ flux tubes was very normal for Kp=3 conditions and closely followed model patterns for convection between the pole and the midnight auroral zone. However, over shorter space‐time dimensions the E⊥ field is observed to be irregular; this also is a normal polar cap condition. From the analysis of field aligned motions in terms of the potential changes required in the equation of motion to match the altitude versus time observations: (1) E∥ fields do not appear below 1400 km, (2) between 1500 and 4200 km the changes in energy are typically 20–40 eV with a 71 eV maximum, (3) between 4200 and 15,000 km maximum values are in the range 80–720 eV with the highest values coming from the highest latitude releases, and (4) in the case of one release a 6 keV acceleration appears above 15,800 km. These changes appear as both accelerating (upward E∥) and decelerating (downward E∥) fields with an apparent periodicity of 3 to 4 min and are in phase at all four locations for 3, and possibly 4 or 5, cycles within the limitations imposed by a 1 min resolution and data gaps. This apparent wave characteristic could, under selective error assumptions, result from several impulsive decelerations superimposed on a more general, but variable, accelerating field. This possibility is considered to be less likely than a hydromagnetic wave association. The unique capabilities for measuring very weak fields and for separating temporal and spatial variations may explain the lack of precedent from previous E∥ measurements.

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Section: Neutral Cloud Expansionmentioning

confidence: 95%

The Cameo Barium Releases: E_∥ fields over the polar cap

Heppner¹,

Miller²,

Pongratz³

et al. 1981

J. Geophys. Res.

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The initial behavior of high altitude barium releases—I. The particulate ring

Best

Huffman

1974

Journal of Atmospheric and Terrestrial Physics

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High‐altitude gas releases: transition from collisionless flow to diffusive flow in a nonuniform atmosphere

Bernhardt¹

1979

J. Geophys. Res.

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Vapors, released at high altitudes from rockets or the Space Shuttle, may travel many hundreds of kilometers before coming to rest. An understanding of the effects produced by these releases requires knowledge of the vapor flow. In the tenuous upper atmosphere, the injected gases expand from a collisionless to a collision‐dominated state. In this paper, this process is described by the Boltzmann equation with the Krook collision integral. The theory is applied to supersonic releases into a nonuniform atmosphere. The model predicts elongation and heating of the vapor trails due to collisions. The theory may be applied to a wide range of experiments whose objectives include the formation of ionospheric depletions, the triggering of instabilities, the generation of gravity waves, and the injection of neutrals as luminous tracers.

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The initial behavior of high altitude barium releases—II. The expanding vapor cloud

Cited by 4 publications

References 9 publications

The Cameo Barium Releases: E_∥ fields over the polar cap

The Cameo Barium Releases: E_∥ fields over the polar cap

The initial behavior of high altitude barium releases—I. The particulate ring

High‐altitude gas releases: transition from collisionless flow to diffusive flow in a nonuniform atmosphere

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The initial behavior of high altitude barium releases—II. The expanding vapor cloud

Cited by 4 publications

References 9 publications

The Cameo Barium Releases: E∥ fields over the polar cap

The Cameo Barium Releases: E∥ fields over the polar cap

The initial behavior of high altitude barium releases—I. The particulate ring

High‐altitude gas releases: transition from collisionless flow to diffusive flow in a nonuniform atmosphere

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The Cameo Barium Releases: E_∥ fields over the polar cap

The Cameo Barium Releases: E_∥ fields over the polar cap