Engineering topics

Arnoldy, R. L.

Publications and source records attributed to Arnoldy, R. L..

At least 37 records · Page 2

NASA NTRS1988

Observations of the plasma environment during an active ionospheric ion beam

This paper presents detailed data on positive ion flux observations acquired during an active rocket-borne ion beam injection experiment, using the hemispheric electrostatic energy and pitch angle spectrometer (HEEPS) which was separated from the beam-emitting payload by distances along and across geomagnetic field lines which varied systematically during the experiment. The data obtained by the HEEPS illustrate a number of outstanding features of the ion flux environment near the HEEPS instrument during beam operations, some of which are not understood. It is shown that particle, field, and photometric data support a picture of particularly intense beam-plasma interactions in the immediate vicinity of the beam-emitting payload.

Pollock, C. J.↗

NASA NTRS1988

Ion beam releases at rocket altitudes

NASA Flight 29.015 was the third in a series of flights to study the electrodynamics of man-produced ion beams in the ionosphere. Much like an earlier flight (Moore at al., 1982 and 1983; Kaufman et al., 1985), plasma releases perpendicular to the earth's B field result in ions being measured, often at reduced energies, several hundred meters from the source along the magnetic field. Releases at 200-eV energy parallel to B, however, result in over-200-eV ions measured above the source. In addition, parallel ion releases result in two additional populations of ions seen near 90-deg pitch angle; one near the energy of the generator, and the other at considerably lower energy. The energization of parallel ions could result from the same process by which electrons were accelerated to the generator payload as measured on an earlier flight, presumably due to blockage of natural field-aligned currents by gun-related wave turbulence. This turbulence is also undoubtedly inherent in the mechanism by which a parallel beam of ions creates a perpendicular component.

Pollock, C. J.↗

NASA NTRS1987

Initial results from the operation of two argon ion generators in the auroral ionosphere

Two argon ion generators have been lofted by sounding rockets in order to investigate ion beam dynamics and beam effects on the ionosphere, and auroral electrodynamics during rocket passage over auroral arcs. The ion generators were on a subpayload that was separated from the main payload early in the flight. The main payload conducted the diagnostic measurements during ion beam operations. Evidence of heating of the ionosphere around the subpayload during each ion beam emission is noted.

Erlandson, R. E.↗

NASA NTRS1986

Preferential O(+) heating in the topside ionosphere

Observations of preferential heating of the ionospheric majority ion species O(+), are reported. The heating took the form of a hot (few electron volts) tail in the upgoing thermal O(+). No such hot tail was observed in the light ion distributions. An event observed at 700-800 km altitude was highly anisotropic with a much hotter tail transverse to the local magnetic field. A series of events observed at 250-375 km were more nearly isotropic with respect to the local magnetic field. Broadband plasma wave emission near the lower hybrid resonance was observed in conjunction with the high altitude event. The low altitude events were tightly correlated with auroral electron precipitation, but broadband lower hybrid emission was much reduced. The observed hot tail formation is sufficient to produce significant O(+) ion transport to higher altitude auroral acceleration regions.

Moore, T. E.↗

NASA NTRS1986

Relations between morning sector Pi 1 pulsation activity and particle and field characteristics observed by the DE 2 satellite

Ground-based magnetometer, photometer, and riometer data are combined with low-altitude particle and electric and magnetic field data from the DE-2 spacecraft to provide a more complete characterization of the magnetospheric and tropospheric environment in which morning sector asymmetric Pi 1 pulsations are observed. The results of the study are in agreement with recent conclusions that morning sector asymmetric Pi 1 pulsations are physically related to pulsating aurorae. Precipitation of energetic electrons (E greater than 35 keV) coincides in every instance with the occurrence of these pulsations.

Engebretson, M. J.↗

NASA NTRS1986

An auroral arc in the late evening plasma flow reversal

The late evening plasma flow reversal over Alaska on January 27, 1980 and changes associated with an auroral arc are examined on the basis of radar observations and rocket measurements. In particular, attention is given to changes in the plasma flow patterns resulting from a small substorm and to several effects associated with the auroral arc, such as an inverted V electron energy spectrum and, on the equatorial edge, an intense burst of auroral hiss and a very thin sheet of field-aligned electrons. Details of the experimental payload and geophysical conditions of the launch are included.

Cahill, L. J., Jr.↗

NASA NTRS1986

Dayside pulsation events near the plasmapause

Magnetic field observations of four dayside pulsation events detected near the equatorial plasmapause region on August 23, 24, September 30, and October 10, 1982 are examined. The wave characteristics and the magnetic components of the pulsation events obtained from DE-1 satellite data and ground data from Siple, Antarctica are described and compared. The pulsations displayed similar complex wave structures; long period transverse waves greater than 100 s are the fundamental mode oscillations of magnetic shells and short period waves of 20-40 s are superimposed on them. It is observed that wave bursts are present in all frequency ranges. The relationship between eigenperiod and the magnetic shell is studied.

Lin, N. G.↗

NASA NTRS1986

Argon ions injected parallel and perpendicular to the magnetic field

Preliminary results are reported of measurements obtained with the 0-10-kHz electric-field plasma-wave receivers and single-particle ion detectors of the ARCS-3 sounding-rocket payload over the auroral oval on February 10, 1985, after downward/field-parallel or transverse-spiral injection of Ar ions from the accelerator subpayload (separating itself at 2.3 m/s). The data are presented graphically and briefly characterized. The waves induced by the parallel injections are found to be much weaker than those induced by the perpendicular injections. In addition to the expected response to the Ar beam, an ion flux at pitch angle 90 deg was detected during the second parallel injection.

Erlandson, R. E.↗

NASA NTRS1985

Heavy ion beam-ionosphere interactions - Electron acceleration

Moore et al. (1982) described a number of unexpected effects which were observed during the first Argon Release Controlled Study (ARCS 1, or rocket flight 29:014). The present paper provides a description of detailed analyses of the interaction of the argon beam with the ionosphere. An important feature of the considered test was that all detectors and the Ar(+) gun remained attached to the rocket throughout the flight. It is pointed out that the most dramatic effect of ion gun operation on ARCS 1 involved large changes in the fluxes of electrons with energies below about 600 eV. The observations are discussed, taking into account the distribution functions, azimuth dependence, and electron and ion trajectories. Attention is given to the perpendicular ion beam, the parallel ion beam, the acceleration of downgoing and upgoing electrons, and aspects of wave generation.

Kaufmann, R. L.↗

NASA NTRS1985

Low-altitude field-aligned electrons

Earlier measurements of field-aligned electrons are reexamined in the light of the more recent and comprehensive data available from both rocket and satellite observations. It is found that: (1) field aligned electrons are associated with evening, midnight, and cusp auroras; (2) rocket data associate the field aligned electrons with active auroral forms and on the edges of moving discrete arcs, predominantly the leading edge; and (3) the spatial/temporal scale of the field-aligned events seen by satellites is a few seconds or tens of kilometers, while the rocket time scale extends from seconds to hundreds of seconds. Recent acceleration mechanisms involving turbulence are discussed.

Arnoldy, R. L.↗

NASA NTRS1985

The energization of electrons and ions by electron beams injected in the ionosphere

This paper represents a continuation of an investigation of the nature and origin of the particle populations associated with an electron beam-emitting rocket experiment in the ionosphere. In this investigation, the intense flux of suprathermal electrons created around such a rocket has been studied by several groups. Arnoldy and Winckler (1981) have discussed the vehicle floating potential problem. The present paper is concerned with results which have been obtained from the Echo 4 and 5 experiments considered by Swanson (1983). Attention is given to instrumentation, suprathermal electrons, thermal ions, energetic ions, and ion resonances.

Arnoldy, R. L.↗

NASA NTRS1984

Observation of an oscillating magnetic field shell at three locations

The complex magnetic-pulsation event near magnetic shell L = 4.5 at 1830-1930 UT on July 14, 1982, is characterized on the basis of observations obtained by the DE-1 satellite near the equator and by magnetic stations at Siple, Antarctica, and Roberval, Quebec, Canada, at opposite ends of the L = 4.2 field line. The data are presented graphically and discussed in the light of theoretical models. The main features (in sequence) observed were a brief 120-sec compressional pulsation, a 5-nT 180-sec transverse pulsation, a weak 44-sec transverse pulsation, and a rapidly developing 240-sec azimuthal pulsation. The 180-sec and 240-sec pulsations are found to be large-scale toroidal oscillations on one and two resonant shells, respectively, while the 44-sec pulsation appears to be more localized.

Cahill, L. J.↗

NASA NTRS1984

On the relationship between morning sector irregular magnetic pulsations and field aligned currents

For three magnetically disturbed days in early 1980, data from south polar masses of the Magsat satellite are compared with data from search coil magnetometer, riometer, and photometer instrumentation at Siple, Antarctica. It is found that during each Magsat polar pass in the morning sector, the level of Pi 1 activity correlates well with the intensities of three-dimensional current systems. Fine structure is often observed in the field-aligned currents during periods of intense Pi activity. Among the Birkeland currents are 2-s to 10-s (16-80 km) structured perturbations; these are evident in the transverse components of the field and are thought to indicate filamentary currents. Pi 1 amplitudes are found to be considerably larger when region 2 Birkeland currents are overhead than when they are not. In one case, detailed features are identified in the high-resolution Magsat magnetic field data that may be current fluctuations related to asymmetric Pi 1.

Engebretson, M. J.↗

NASA NTRS1983

Plasma jet effects on the ionospheric plasma

Heavy ion beams were injected into the ionospheric plasma (experiments ARCS 1 and ARCS 2). In ARCS 1, operation of a 25eV argon ion source, mounted on a plasma diagnostic payload, produced an accelerated electron population; broadband electric field turbulence; large, spin synchronized electric field perturbations; and depletions of thermal ions. In ARCS 2, the ion source was deployed upward along the local magnetic field direction away from the diagnostic payload, and observed effects are contained within several meters of the ion source. However, enhanced wave levels near the LHR frequency are observed at distances up to 1 km, as are the injected ions themselves. A measurement of the dominant wavelength of the enhanced waves is consistent with an inference based upon the accelerated electron population seen in ARCS 1. This electron population is not evident during ARCS 2.

Moore, T. E.↗

NASA NTRS1982

Anomalous auroral electron distributions due to an artificial ion beam in the ionosphere

Results are reported for the perturbation of the auroral ionosphere by the operation of an ion gun which injected about 100 mA of 25-eV Ar(+) ions at upgoing pitch angles over a discrete auroral arc. The major effects observed were the excitation of intense broadband electric field fluctuations at zero-10 kHz, and the appearance of streaming and isotropic heating in different parts of superthermal electron velocity space. A scenario is explored in which electron runaway or streaming is expected between the trapping speed and the critical velocity for cyclotron interactions with the waves, where the streaming electrons carry the current that would be carried by thermals or energetic electrons in the absence of the waves. A current of about 1.0 microA/sq m is carried by the streaming electrons. The gun-associated electrons were anomalous in the sense that their anisotropy was the opposite of that observed in the natural aurora.

Moore, T. E.↗

NASA NTRS1982

Plasma injection events at synchronous orbit related to positive Dst

AST 6 spacecraft synchronous orbit measurements are compared with space and ground data in a study of plasma effects related to SI and SC magnetic perturbations. It is found that synchronous orbit plasma injections related to the sudden phenomena are similar to those associated with substorms, although the former occur at all local times. The synchronous orbit plasma injections are interpreted as the co-location of particle boundaries on an inward propagating front and the compression magnetic pulse associated with SI and SC events is seen as responsible for the co-location of the boundaries and their inward propagation. The positive Dst magnetic pulse plays a role similar to that of the magnetic tail reconfiguration pulse associated with substorms, and evidence is shown that positive Dst enhances magnetospheric convection independently of interplanetary magnetic field direction

Arnoldy, R. L.↗

NASA NTRS1982

Plasma pitch angle distributions near the substorm injection front

ATS-6 spacecraft hot plasma instrument data obtained during January, 1980 is presented, which provides electron and ion pitch distributions in the vicinity of an earthward-propagating, substorm-associated abrupt plasma change near synchronous orbit. Evidence is found of symmetric atmospheric source cones for few 100-eV electrons after front passage, supporting both (1) concept of atmospheric electron degradation of the hot, high-altitude plasma, and (2) the proposal that the injection front is a moving, precipitation-flow boundary between the hot plasma and the cooler plasma that has become spectrally degraded via interaction with the atmosphere. The enhanced hot plasma electron intensities appearing in association with front passage exhibit a modest, field-aligned anisotropy with minima at pitch angles characteristic of symmetric loss cones, consistent with mirror compression of the electrons on inward-collapsing field lines.

Moore, T. E.↗

NASA NTRS1981

Propagating substorm injection fronts

It is argued that a series of two-satellite observations leads to a clarification of substorm plasma injection, in which boundary motion plays a major role. Emphasis is put on a type of event characterized by abrupt, dispersionless changes in electron intensity and a coincident perturbation that consists of both a field magnitude increase and a small rotation toward more dipolar orientation. Comparing plasma observations at two points, it is found that in active, preinjection conditions the two most important features of the plasma sheet are: (1) the low-energy convection boundary for near-zero energy particles, determined by the magnitude of the large-scale convection electric field; and (2) the precipitation-flow boundary layer between the hot plasma sheet and the atmospherically contaminated inner plasma sheet.

Moore, T. E.↗