Engineering topics

Moore, T. E.

Publications and source records attributed to Moore, T. E..

At least 163 records · Page 9

NASA NTRS1986

Observations of coherent transverse ion acceleration

DE-1 retarding ion mass spectrometer (RIMS) observations of transverse O(+) acceleration in the topside ionosphere are reported and analyzed. The operation and capabilities of RIMS are reviewed, and the data are presented graphically and characterized in detail. Torus or ring O(+) distributions with radii 10 km/s are observed, consistent with coherent transverse acceleration to 10-eV energies in the bulk-plasma reference frame, and conical hot tails at energies above the 50-eV RIMS maximum are noted. Possible mechanisms for these phenomena are discussed.

Moore, T. E.↗

NASA NTRS1986

Transport of accelerated low-energy ions in the polar magnetosphere

Recent satellite observations of low-energy (0-50 eV) ionospheric ions in the polar cap magnetosphere suggest that these ions are injected at the dayside cleft topside ionosphere. Using a two-dimensional kinetic model, several consequences of this ion flow from a narrow cleft source have been simulated and observed. These include: (1) the Kp/convection-dependent filling of the polar magnetosphere with ionospheric heavy ions, in which these ions are 'blown' further into the polar cap magnetosphere from the cleft during high Kp/convection; (2) the mass- and energy-dependent dispersion of these ions, as in a kind of 'geomagnetic spectrometer'; (3) the creation of 'supersonic' ion outflows as a natural velocity-filter effect of this geomagnetic spectrometer; and (4) the 'parabolic flow' of gravitationally bound heavy ions from the cleft ionosphere resulting in downward flow into the polar cap.

Horwitz, J. L.↗

NASA NTRS1986

Ion energization in upwelling ion events

A source of H(+), He(+), O(+), and N(+) outflow from the ionosphere has been identified near the polar cusp/cleft using the Dynamics Explorer/retarding ion mass spectrometer data set. This ion outflow termed 'upwelling ions' is characterized by large outfluxes of H(+) and O(+) ions and high transverse ion temperatures. This paper reports on the associated particle and field characteristics of one such upwelling ion event on March 12, 1982. Field-aligned currents and strong E x B convection channels are associated with the event as well as strong broadband plasma wave emission. One or all of these sources may play an important role in the ion energization in this region.

Waite, J. H., Jr.↗

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 NTRS1986

Solar wind control of the Geomagnetic Mass Spectrometer

Evidence from Dynamics Explorer retarding-ion mass-spectrometer data collected between 1981 and 1983 for the mass dispersion of ionospheric plasma in the polar cap, known as the Geomagnetic Mass Spectrometer, is discussed, and implications of this new source of ionospheric ions for the magnetosphere are considered. A localized source of energization of ionspheric H(+), He(+), O(+) and N(+) ions in the polar cusp yields a source of upswelling plasma that is transported into the magnetosphere, and equal heating of the ion species results in field-aligned flow velocities which are inversely proportional to the square root of the ion mass. The present phenomenon is produced by the resulting velocity filter effect of solar-driven ExB ion convection. The influence of solar wind conditions on the outflow via the polar cap ExB convection pattern is also discussed.

Waite, J. H., Jr.↗

NASA NTRS1985

Supersonic ion outflows in the polar magnetosphere via the geomagnetic spectrometer

Observations of 'supersonic' O(+) outflows by DE-1 in the polar magnetosphere are interpreted as a velocity-filter effect resulting from the transport of these low energy ions from a horizontally narrow source associated with the polar cleft topside ionosphere into the polar cap magnetosphere. Under certain simplifying circumstances, it is shown that the 'Mach number' for the flow is essentially a geometrically determined quantity, approximately the ratio of the horizontal distance of the observation location to the source over the horizontal width of the source. A recently developed two-dimensional kinetic model of ion transport in the polar magnetosphere is used to calculate distribution functions and the associated bulk flow parameters, and these calculated quantities are compared with measured flow parameters from DE-1.

Horwitz, J. L.↗

NASA NTRS1985

DE 1 RIMS operational characteristics

The Retarding Ion Mass Spectrometer (RIMS) on the Dynamics Explorer 1 spacecraft observes both the thermal and superthermal (50 eV) ions of the ionosphere and inner magnetosphere. It is capable of measuring the detailed species distribution function of these ions in many cases. It was equipped with an integral electrometer to permit in-flight calibration of the detector sensitivities and variations thereof. A guide to understanding the RIMS data set is given. The reduction process from count rates to physical quantities is discussed in some detail. The procedure used to establish in-flight calibration is described, and results of a comparison with densities from plasma wave measurements are provided. Finally, a discussion is provided of various anomalies in the data set, including changes of channeltron efficiency with time, spin modulation of the axial sensor heads, apparent potential differences between the sensor heads, and failures of the radial head retarding potential sweep and of the -Z axial head aperture plane bias. Studies of the RIMS data set should be conducted only with a thorough awareness of the material presented here, or in collaboration with one of the scientists actively involved with RIMS data analysis.

Olsen, R. C.↗

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

The cleft ion fountain

Low-energy ionospheric ions, injected into the magnetosphere at the dayside cleft, are studied using data for the retarding ion mass spectrometer experiment on the Dynamics Explorer 1 satellite. It is concluded that the upwelling ion events identified in the vicinity of the cleft may be regarded as an ion fountain, supplying low-energy ions to the entire polar magnetosphere when convection is antisunward and strong. It is also shown that heavy ion flows can be downward in the polar cap, consistent with 'parabolic' trajectories of heavy ions from this cleft ion fountain.

Lockwood, M.↗

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

Evidence for ion heat flux in the light ion polar wind

Cold flowing hydrogen and helium ions have been observed using the retarding ion mass spectrometer on board the Dynamics Explorer 1 spacecraft in the dayside magnetosphere at subauroral latitudes. The ions show a marked flux asymmetry with respect to the relative wind direction. The observed data are fitted by a model of drifting Maxwellian distributions perturbed by a first order-Spritzer-Haerm heat flux distribution function. It is shown that both ion species are supersonic just equatorward of the auroral zone at L = 14, and the shape of asymmetry and direction of the asymmetry are consistent with the presence of an upward heat flux. At L = 6, both species evolve smoothly into warmer subsonic upward flows with downward heat fluxes. In the case of subsonic flows the downward heat flux implies a significant heat source at higher altitudes. Spin curves of the spectrometer count rate versus the spin phase angle are provided.

Biddle, A. P.↗

NASA NTRS1985

The geomagnetic mass spectrometer - Mass and energy dispersions of ionospheric ion flows into the magnetosphere

Observations of ion flows in the polar magnetosphere, made by the retarding ion mass spectrometer on NASA's Dynamics Explorer (DE) 1, are compared with those made simultaneously in the topside ionosphere by the ion drift meter on the lower-altitude DE 2 spacecraft. The results show the dayside auroral ionosphere to be a significant and highly persistent source of plasma for the magnetosphere. The upwelling ionospheric ions are spatially dispersed, according to both their energy and mass, by the combined actions of the geomagnetic field and the dawn-to-dusk convection electric field, in an effect analogous to the operation of an ion mass spectrometer.

Lockwood, M.↗

NASA NTRS1985

A new source of suprathermal O(+) ions near the dayside polar cap boundary

A large number of data on suprathermal O(+) ions taken during the retarding ion mass spectrometer (RIMS) experiment aboard the DE 1 satellite are surveyed. Examples are found of low-energy, upflowing O(+) which are consistent with one or more of the proposed ionospheric escape mechanisms. These include transversely accelerated O(+) ions, indicating low-altitude transverse acceleration, and O(+) field-aligned flows which indicate low-altitude parallel acceleration by either ambipolar or current-driven electric fields. However, by far the most common pitch angle distribution of escaping O(+) is found to be a new type of O(+) flow event which provides evidence for both perpendicular and parallel ion acceleration below the satellite and is found exclusively in the lower latitudes of the dayside polar cap. All species of ions are observed to move upward during these events, with an upward heat flux.

Lockwood, M.↗

NASA NTRS1985

Auroral zone effects on hydrogen geocorona structure and variability

The effect of diurnal and magnetospheric modulations on the structure of the hydrogen geocorona is analyzed on the basis of recent observations. Particular attention is given to the enhancement of neutral escape by plasma effects, including the recently observed phenomenon of low-altitude ion acceleration. It is found that, while significant fluxes of neutral H should be produced by transverse ion acceleration in the auroral zone, the process is probably insufficient to account for the observed polar depletion of hydrogen atoms. Analysis of recent exospheric temperature measurements from the Dynamics Explorer-2 satellite suggest that neutral heating in and near the high latitude cusp may be the major contributor to depleted atomic hydrogen densities at high latitudes. Altitude profiles of the production rates for escaping neutral hydrogen atoms during periods of maximum, minimum, and typical solar activity are provided.

Moore, T. E.↗

NASA NTRS1985

Superthermal ion signatures of auroral acceleration processes

The occurrence of non-Maxwellian superthermal features in the auroral topside ionosphere distribution functions has been documented by means of the retarding ion mass spectrometer on the Dynamics Explorer 1 spacecraft. Attention is given to a representative sampling of the observed features and their spatial morphology, as observed at altitudes ranging from a few thousand km to a few earth radii. The observations in question reveal a clear distinction between classical polar wind ion outflow and O(+)-enhanced superthermal flows, and confirm the importance of low altitude transverse acceleration in ionospheric plasma transport, as suggested by previous observations.

Moore, T. E.↗

NASA NTRS1984

Superthermal ionospheric outflows

In recent years observations have shown that the terrestrial ionosphere serves as a significant source of the hot plasma in the magnetosphere. These findings imply that cold plasma flows upward to great altitudes and at some point along the way gains energies much larger than typical ionospheric values. The present investigation is mainly concerned with observations of ionospheric outflows at energies higher than those predicted by ambipolar wind models but lower than those associated with keV auroral ion acceleration, giving particular attention to the energy range from a few to a few hundred electron volts. The ion flows in the energy range intermediate between polar wind and keV auroral ion beams are called superthermal ion outflows. It is shown that recent observations of superthermal ion outflows from the terrestrial ionosphere are related to theoretical models of the topside ionosphere.

Moore, T. E.↗

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.↗