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Volume 40, Issue 10
Displaying 1-12 of 12 articles from this issue
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I. Kimura, H. Matsumoto1988 Volume 40 Issue 10 Pages 1129
Published: 1988
Released on J-STAGE: August 11, 2011
JOURNAL FREE ACCESSDownload PDF (75K) -
Richard L. DOWDEN1988 Volume 40 Issue 10 Pages 1131-1140
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSGeneration of electrical power at any frequency in this range is quite simple. Significant generation of waves at frequencies below, say, 5kHz requires antennas some kilometres in length and height above the ground plane. Antenna methods used with some success to probe the magnetosphere and ionosphere are reviewed: balloon lofted vertical monopoles (Alaska and N. Z.), a dipole over ice (Siple), borrowed power lines (arctic Norway and N. Z.), electrojet modulation (U. S. S. R. and Norway).View full abstractDownload PDF (808K) -
M. C. LEE, K. M. GROVES, C. P. LIAO, D. R. RIVAS, S. P. KUO1988 Volume 40 Issue 10 Pages 1141-1145
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThe combined operation of an HF or MF ground transmitter and a VLF transmitter for enhanced ionospheric heating is discussed. The HF or MF transmitter, operated in a pulsed mode, can preferentially produce short-scale density striations that can render the nonlinear mode conversion of the subsequently launched VLF waves into lower hybrid waves. In addition to the mode conversion process, the VLF waves, if intense enough, can also excite meter-scale density striations and lower hybrid waves via parametric instabilities. Intensified density striations and enhanced airglow are expected, and they can be detected by incoherent backscatter radars and photometers, respectively. The feasibility and planning of the proposed experiments are addressed.View full abstractDownload PDF (563K) -
William J. BURKE, Gregory P. GINET, Elena VILLALON, Michael A. HEINEMA ...1988 Volume 40 Issue 10 Pages 1147-1159
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThe relativistic equations of motion have been analyzed for electrons in magnetized plasmas and externally imposed electromagnetic fields that propagate at arbitrary angles to the background magnetic field. The electron energy is obtained from a set of non-linear differential equations as functions of time, initial conditions and cyclotron harmonic numbers. For a given cyclotron resonance the energy oscillates in time within the limits of a potential well. Stochastic acceleration occurs if the widths of hamiltonian potentials overlap. Numerical analyses suggest that, at wave energy fluxes in excess of 108mW/m2, initially cold electrons can be accelerated to energies of several MeV in less than a millisecond. Practical attempts to validate the theory with a series of planned rocket flights over the HIPAS facility in Alaska are discussed. The HIPAS antennas will be used to irradiate the magnetic mirror points of 10-40keV electrons emitted from the ECHO 7 rocket in the early winter of 1988. Follow-on rocket experiments to exploit the wave amplification properties of the ionospheric “radio window” are described.View full abstractDownload PDF (979K) -
K. AKIMOTO, M. GALVEZ, S. P. GARY, A. G. SGRO, D. WINSKE1988 Volume 40 Issue 10 Pages 1161-1191
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSLarge amplitude flute-like modes on plasmas expanding in external magnetic fields have been observed in both space and laboratory experiments. In this paper we review relevant experimental, theoretical, and numerical research with particular emphasis on the work that has been carried out at Los Alamos. Theoretical research on the diocotron instability and both the electrostatic and electromagnetic aspects of the lower-hybrid drift instability is summarized. Simulation results based on a hybrid code with finite electron mass, an electrostatic particle code, and an electromagnetic particle code are also described. We conclude that the lower hybrid drift instability rather than the diocotron instability is the likely source of the flute modes but that nonlinear effects must be invoked to explain the wavelengths of the observed structures. A number of unresolved issues related to the theory and experiments are also discussed.View full abstractDownload PDF (4276K) -
Susumu SASAKI1988 Volume 40 Issue 10 Pages 1193-1204
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSNeutral gas-plasma interaction in space was studied in the SEPAC experiment on the Space Shuttle, STS-9 mission. Nitrogen gas of 1023 molecules and argon gas of 1021 molecules were repeatedly released from the orbiter at the height of 245km into the ionosphere. During the gas release, an enhancement of ambient plasma density and a fluctuation of orbital potential were detected. When the gas was injected together with a high speed plasma, a CVI-like phenomenon was observed. This paper summarizes the results of the gas-plasma interaction observed in the SEPAC experiment and gives a possible explanation of the observation.View full abstractDownload PDF (1343K) -
S. MACHIDA, C. K. GOERTZ, G. LU1988 Volume 40 Issue 10 Pages 1205-1219
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSSimulations of the Critical Ionization Velocity (CIV) for a neutral gas cloud moving across the static magnetic field are made. We treat a low-β plasma and use a 2-1/2 D electrostatic code linked with our Plasma and Neutral Interaction Code (PANIC). Our study is focused on the understanding of the interface between the neutral gas cloud and the surrounding plasma where the strong interaction takes place. We assume the existence of some hot electrons in the ambient plasma to provide a seed ionization for CIV. When the ionization starts a sheath-like structure is formed at the surface of the neutral gas (Ionizing Front). In that region the crossfield component of the electric field causes the electron to E×B drift with a velocity of the order of the neutral gas velocity times the square root of the ion to electron mass ratio. Thus the kinetic energy of the drifting electrons can be large enough for electron impact ionization. In addition a diamagnetic drift of the electron occurs due to the number density and temperature inhomogeneity in the ionization front. These drift currents excite the lower-hybrid waves with the wave k-vectors almost perpendicular to the neutral flow and magnetic field again resulting in electron heating and additional ionization. The overall structure is studied by developing a simple analytic model as well as making simulation runs.View full abstractDownload PDF (1053K) -
T. NEUBERT, J. G. HAWKINS, G. D. REEVES, P. M. BANKS, R. I. BUSH, P. R ...1988 Volume 40 Issue 10 Pages 1221-1233
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSDuring the Spacelab-2 mission of July, 1985, electron beams (1keV, 50-150mA) pulsed at ELF and VLF frequencies were emitted from the Space Shuttle Orbiter. The wave fields generated by the beam were monitored by a Plasma Diagnostics Package (PDP), which was released as a free-flying sub-satellite during a six hour period. Measurements of the Orbiter potential and the return current during beam emissions were obtained from a Charge and Current Probe (CCP) mounted in the payload bay. Results from the PDP and CCP are presented.View full abstractDownload PDF (2599K) -
A Simulation StudyP. L. PRITCHETT, R. M. WINGLEE1988 Volume 40 Issue 10 Pages 1235-1256
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSA two-dimensional, isolated-system electrostatic simulation model is used to investigate the plasma environment in the vicinity of a spacecraft during the injection of dense electron beams. The nature of the injection process is determined primarily by the relative value of two characteristic time scales: the beam stagnation time ts and the plasma response time trp. When ts<trp, spacecraft charging is significant and most of the beam electrons are drawn back into the spacecraft. When ts>trp, vehicle charging is reduced and the beam propagates away from the source. In this latter case there is strong beam-plasma turbulence which destroys the coherence of the beam within one or two gyroperiods. The spatial distribution of the beam has the form of a hollow cylinder near the source. As the beam propagates away from the source, the cylinder becomes increasingly filled. Return currents are associated with the field-aligned flow of ambient electrons, while current closure is provided primarily by the cross-field motion of the ions. Energization of the ambient electrons may increase the apparent beam size as determined from low-light TV images.View full abstractDownload PDF (1890K) -
Paul J. KELLOGG, Steven J. MONSON1988 Volume 40 Issue 10 Pages 1257-1267
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSWe present some limited results obtained from the flight of SCEX II, from Poker Flat, Alaska, on January 31, 1987. Some of the experiments were aimed at understanding neutralization processes around an electron beam emitting rocket. It was expected that electrons drifting in the strong electric fields around the charged rocket would acquire sufficient energy to ionize neutrals, and that the resulting ions would be hurled outward at energies up to the rocket potential. Three hemispherical retarding potential analyzers were ejected from the main payload to measure these ions. This experiment was successful, in spite of arcs which developed around the batteries for the electron guns, which degraded the emitted electron beam to unusable levels except for about 8 sec of the flight. Ions were observed at energies up to 175eV, the limit of the analyzers.
The main payload carried, in addition to the electron accelerator, two arms with conducting elements to act as Langmuir probes, and to measure floating potentials. These measurements show that fields sufficient to accelerate electrons to ionizing energies were present around the rocket.View full abstractDownload PDF (800K) -
Nobuki KAWASHIMA1988 Volume 40 Issue 10 Pages 1269-1281
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSFuture of the electron beam experiment is discussed based on the experience of the space shuttle experiment SEPAC (Space Experiment with Particle Accelerators) on Spacelab 1. After a review of the SEPAC achievement, problems which the electron beam experiment is facing are discussed and the importance of finding new applications of the beam experiment in space such as the electron beam antenna for low frequency wave excitation is emphasized.View full abstractDownload PDF (2371K) -
Shigeyuki MINAMI, Peter J. BAUM, George KAMIN, Yoshio TAKEYA, R. Steph ...1988 Volume 40 Issue 10 Pages 1283-1302
Published: 1988
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSLaboratory plasma plumes injected into magnetized plasma flows simulate the formation of cometary magnetospheres. Likewise, in our laboratories plasma plumes are injected into the tail of the simulated earth's magnetosphere produced by an interaction between the simulated solar wind and a magnetic dipole. The behavior of laboratory artificial plasma plumes injected into the magnetized plasma flow is discussed in conjunction with the AMPTE artificial comet experiments and other active chemical release experiments in space.View full abstractDownload PDF (9190K)
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