Space Experiments with Particle Accelerators

Obayashi, T.; Kawashima, Nobuki; Kuriki, K.; Nagatomo, Makoto; Ninomiya, Keiken; Sasaki, Susumu; Yanagisawa, Masahisa; Kudo, Isao; Ejiri, Masaki; Roberts, W. T.; Chappell, C. R.; Reasoner, D. L.; Burch, J. L.; Taylor, William; Banks, Peter M.; Williamson, Paul; Garriott, O. K.

doi:10.1126/science.225.4658.195

Cited by 43 publications

(12 citation statements)

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“…The S EPAC experiment on the ATLAS 1 mission was designed to accelerate electron beams up to energies of 6.25 keV with beam currents of up to 1.21 A. A previous flight of this experiment [Obayashi et al, 1984] demonstrated that the spacecraft potential must be actively controlled to achieve such high beam energy and current. This was accomplished on the ATLAS 1 mission by (1) flying the shuttle, tail-first during the artificial aurora experiments in order to collect neutralizing plasma on the conducting engine farings, (2) including three additional conducting spheres in the shuttle cargo bay, and, (3) perhaps most importantly, releasing Xe + ions during the beam pulses to neutralize the charging effects of the significant electron beam current.…”

Section: Preliminary Resultsmentioning

confidence: 99%

Imaging of artificial aurora in the upper atmosphere

Mende¹,

Fuselier²,

Geller³

et al. 1995

J. Geophys. Res.

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We use continuum (white light) and filtered (427.8 nm) images from the Atmospheric Emissions Photometric Imaging (AEPI) experiment on the Atmospheric Laboratory for Applications and Science (ATLAS) 1 shutfie mission to investigate the shape and evolution of artificial auroral patches generated by the Space Experiments with Particle Accelerators (SEPAC)electron beam experiment. Auroral patches generated by this beam experiment are complex and differ in the white light and filtered images. In the white light images, the auroral patch consists of a relatively large, diffuse, and somewhat symmetric head and a tail that is directed approximately opposite the spacecraft velocity vector. From the growth of the tail during a beam pulse, the distance from the imager to the emissions is estimated to be about 200 km, consistent with expectations from a simple model of auroral emissions in the atmosphere. In addition to the auroral patch, an intense, diffuse, and variable background glow filling essentially the entire field of view of the white light imager is seen during the beam pulses. This background glow may be caused by low-energy electrons very near the shutfie. This glow is absent in the filtered images, in which the shape of the auroral patch differed, consisting of a relatively large, diffuse, but more asymmetric head, a tail, and a smaller and less intense spot below the head. Curvature of the magnetic field and spacecraft motion during the 1s filtered images allows an estimate of the relative distance from the shutfie to the head, tail, and small spot. This shape is consistent with head emissions generated relatively near the spacecraft (nearest few kilometers), tail emissions somewhat farther away, and finally the small spot emissions generated the farthest away in the lower atmosphere where the natural auroras would be created. In addition, the shape of these patches in the filtered images suggests that the risetime for the head and tail emissions in the filtered images appears to be longer than that for the small spot emission. The differences between the white light images and the filtered images are consistent with the difference between the emission parent state lifetimes and the energy requirement for the emission production. The white light images contain emissions with long lifetimes, and these emissions which are produced near the observer are swept out of the field of view because they are left behind by the shuttle. This gives a bias toward emissions generated farther from the orbiter. The filtered images contain only the very fast produced N2 + emission with a substantial component generated near the orbiter and with an inverse square law attenuated auroral spot in the lower atmosphere. The presence of the tail and the apparent risetime in the near-field emission suggest that there is a buildup and decay time associated with the hot plasma created by the electron beam.

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Section: Preliminary Resultsmentioning

confidence: 99%

Imaging of artificial aurora in the upper atmosphere

Mende¹,

Fuselier²,

Geller³

et al. 1995

J. Geophys. Res.

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“…(SEPAC) were conducted as part of the ATLAS 1 Spacelab mission from March 24 through April 2, 1992. One of the objectives was to perform artificial aurora experiments from orbit using high-power electron beams and the optical imaging capability of the Atmospheric Emissions Photometric Imaging [Obayashi et al, 1984] showed that at these levels special means of neutralizing the Shutfie spacecraft are necessary; therefore, for ATLAS 1 the SEPAC instrument complement included three 122-cm diameter conductive spheres for charge collection and a 1.6 A hollow-cathode Xe + plasma contactor. The flight data show that the effectiveness of these charge neutralization devices was sufficient for injection of electron beams up to the highest beam currents available with the SEPAC EBA.…”

Section: The Space Experiments With Particle Acceleratorsmentioning

confidence: 99%

Artificial auroras in the upper atmosphere 1. Electron beam injections

Burch

Mende

Kawashima

et al. 1993

Geophysical Research Letters

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Artificial electron beams from the Space Experiments with Particle Accelerators (SEPAC) on the ATLAS 1 Spacelab payload were used to stimulate auroral emissions at southern auroral latitudes. The emitted electron beams were monoenergetic at 6.25 keV and were fired in one‐second pulses every fifteen seconds with currents of 1.21 A. Optical measurements of the beam were made in the vicinity of the Shuttle Orbiter by its on‐board television camera and in the upper atmosphere by the Atmospheric Emissions Photometric Imager (AEPI). AEPI imaged auroral emissions in both white light and at the 427.8 nm N2+ emission line. Energy deposition calculations and the results of previous sounding‐rocket experiments had suggested that emissions with scale sizes of about 130 meters would result from the artificial electron beams with the visible emissions extending from about 110 to 130 km altitudes. In the ATLAS 1 experiments the auroral imaging was performed from the Shuttle, providing a new perspective on the artificial auroras and allowing the emissions to be traced from altitudes near the 295 km Shuttle altitude down to the 110 km level along the curved magnetic field lines.

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“…It is thus straightforward to employ electron beams injected from a space vehicle with controlled parameters to explore Artificial Aurora (AA) generated in the upper atmosphere. Such (active) AA experiments have been conducted from sounding rockets and the Spacelab (e.g., Davis et al, 1971Davis et al, , 1980Hess et al, 1971;Cambou et al, 1975Cambou et al, , 1978Cambou et al, , 1980O'Neil et al, 1978a,b;Maehlum et al, 1980a;Jacobsen, 1982;Obayashi et al, 1984;Neubert et al, 1986;Kawashima, 1988;Goerke et al, 1992;Burch et al, 1993). Besides exploring Artificial Aurora, active electron beam experiments, beginning with the Echo 1 experiment (Hendrickson et al, 1971), used injected beams as probes for studying the remote natural processes along the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

“…Because of the limited scope of this review, the setup of different experiments, as well as the electron and ion injectors and diagnostic suites onboard and on the ground, are described only schematically. The presentation is also limited to sounding rocket experiments at altitudes at and below ∼200 km to avoid the effects of return currents caused by a positive potential of beam-emitting vehicles (e.g., Linson, 1982;Obayashi et al, 1984;Managadze et al, 1988;Frank et al, 1989). The main conclusion of these experiments is that the overall dataset cannot be explained solely by collisional degradation of the beam electrons and requires collisionless beam-plasma interactions (BPI) be taken into account.…”

Section: Introductionmentioning

confidence: 99%

Artificial Aurora Experiments and Application to Natural Aurora

Mishin

2019

Front. Astron. Space Sci.

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A review is given of the effects observed during injections of powerful electron beams from sounding rockets into the upper atmosphere. Data come from in situ particle and wave measurements near a beam-emitting rocket and ground-based optical, wideband radiowave, and radar observations. The overall data cannot be explained solely by collisional degradation of energetic electrons but require collisionless beam-plasma interactions (BPI) be taken into account. The beam-plasma discharge theory describes the features of the region near a beam-emitting rocket, where the beam-excited plasma waves energize plasma electrons, which then ignite the discharge. The observations far beneath the rocket reveal a double-peak structure of artificial auroral rays, which can be understood in terms of the beam-excited strong Langmuir turbulence being affected by collisions of ionospheric electrons. This leads to the enhanced energization of ionospheric electrons in a narrow layer termed the plasma turbulence layer (PTL), which explains the upper peak. Similar double-peak structures or a sharp upper boundary in rayed auroral arcs have been observed in the auroral ionosphere by optical, radar, and rocket observations, and called Enhanced Aurora. A striking resemblance between Enhanced and Artificial Aurora altitude profiles indicates that they are created by the above BPI process which results in the PTL.

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Space Experiments with Particle Accelerators

Cited by 43 publications

References 1 publication

Imaging of artificial aurora in the upper atmosphere

Imaging of artificial aurora in the upper atmosphere

Artificial auroras in the upper atmosphere 1. Electron beam injections

Artificial Aurora Experiments and Application to Natural Aurora

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