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Ungstrup, E.

Publications and source records attributed to Ungstrup, E..

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

AMPAS - A new active experiment mission

A new concept for an active experiments mission is presented: The Active Magnetospheric Particle Acceleration Satellite (AMPAS). It is proposed to fly a dual-payload tethered satellite to study three important areas of magnetopsheric physics: (1) electric and magnetic field structures of the Earth's magnetosphere, (2) electron beam-plasma interactions, and (3) far ultraviolet (FUV) signatures of energetic electron precipitation. The tethered system is to be flown in a gravity-gradient stabilized configuration with a 70 deg circular orbit at altitudes in the range 300-800 km. The upper payload will carry two electron beam accelerators (1-10 keV, 1 A) and a plasma contractor to electrically neutralize the payload, while the lower will carry a complement of optical imaging and plasma diagonstics instrumentation. Upward directed beams are injected to 'sound' electric and magnetic field structures, including parallel electric fields in the auroral region, while simultaneous optical instruments aimed downwards measure characteristics of reflected beam pulses precipitating into the upper atmosphere below the satellite. Downward directed beams, and simultaneous plasma wave, particle and optical measurements, are used for the investigation of beam-plasma interactions and electron precipitation studies. The payloads are to be connected by a 1-6 km long tether to be deployed in stages. The configuration of the beam source and the plasma and optical diagnostics on separate, tethered payloads allows the diagnostics to be performed outside of the disturbed region around the source payload, and plasma wave and particle observations of beam-plasma interactions to be performed at well-defined locations relative to the source.

Neubert, T.↗
NASA NTRS1987

Counterstreaming ion events in the magnetosphere

This paper presents general characteristics of more than 60 counterstreaming ion (CSI) events observed by the ISEE 1 satellite. Often, both oxygen and hydrogen ions at a number of energy levels were observed among the CSIs, but some events showed only one of these ions at one or more energy levels involved. In a number of cases, either only H(+) or O(+) ions at just one energy level were seen counterstreaming, and in a few cases, the CSIs were observed to involve ions of one energy traveling parallel to the magnetic field and ions of another energy traveling simultaneously in the antiparallel direction. Moreover, some of the CSI events correlated well with electric wave activity. It is suggested that, in some CSI events, wave-particle interaction may be involved.

Horita, R. E.↗
NASA NTRS1986

Compositional changes, time and density variations in the magnetosphere associated with Birkeland currents and particle acceleration

Birkeland currents, parallel electric fields and plasma instabilities often occur together in time and space and play an important role in large scale plasma motions between the ionosphere and magnetosphere and along the magnetic field in the magnetosphere. The results of the plasma movements are large density and composition variations in the ionosphere and magnetosphere. Observations from ISIS-2 at 1400 km altitude show large densities with heavy ions dominating in regions with upward Birkeland currents, and low densities and light ions in regions with downward currents. Observations from ISEE-1 in field aligned current regions at 10,000 to 15,000 km altitude show transverse heating of protons and oxygen ions to 250 eV. Because of the different mobility of the protons and oxygen ions the proton flow is important in the beginning of the events but later the outflow becomes almost pure oxygen. Similarly ISEE-1 observations of outgoing field ion beams at 10,000 to 15,000 km altitude show time variations in the H+/O+ ratios and a dominance of O+ later in the events.

Ungstrup, E.↗
NASA NTRS1985

Counterstreaming hydrogen and oxygen ions observed in the magnetosphere on ISEE-1

Counterstreaming ions or ions travelling simultaneously both parallel and antiparallel to the magnetic field direction have been briefly noted in the literature but have not been studied previously in depth. Over 60 counterstreaming ion (CSI) events observed on the ISEE-1 satellite have been studied. They were found to occur at altitudes of about 2 to 8 earth radii on L shells of about 5 to 12 in the evening-to-morning sector from about 1700-0900 LT. Often both oxygen and hydrogen ions at a number of energy levels are counterstreaming but some events show only either oxygen or hydrogen ions involved. One particularly interesting event shows only counterstreaming oxygen ions with 417 eV energy; oxygen ions of lower energy (215 eV) and above (630-17,000 eV) and all the hydrogen ions between 215-17,000 eV energy have lower fluxes and/or nearly isotropic pitch angle distributions. This event correlates well with wave activity in the 17-100 Hz band and is also accompanied by 200 eV downgoing and 400 eV upgoing electrons. Details of this event and the other counterstreaming events are presented.

Horita, R. E.↗
NASA NTRS1983

The mass dependence of wave particle interactions as observed with the ISEE-1 energetic ion mass spectrometer

Simultaneous measurements of the O(+) and H(+) distributions from two transverse acceleration events in the high altitude auroral ionosphere are presented. The data were acquired from the energetic ion mass spectrometer on the ISEE-1 satellite, in the dusk sector, on auroral field lines (L = 8-9), at geocentric radial distances of about 3 earth radii. Temporal and/or spatial fluctuations during the measurement cycle resulted in some scatter of the data points, but the transverse velocity distributions are reasonably well represented by maxwellians at energies in the few hundred eV range. The transverse temperatures were about 60 eV in both cases and no significant differences were observed between the temperatures of the O(+) and H(+). The flux intensities of the two ion species were also generally comparable.

Sharp, R. D.↗
NASA NTRS1983

The Giotto magnetic field investigation

The Giotto spacecraft will carry sensors for investigating the interplanetary magnetic field while en route and the interaction between the solar wind magnetoplasma and Halley's Comet neutral gas outflow during close approach. Giotto will carry an outboard biaxial fluxgate system and inboard electronics. The instrumentation draws 1.2 kW and weighs 1.31 kg. Sampling rates will be 28/sec during close encounter, covering selectable ranges from 16 nT to 65,535 nT. In-flight calibration techniques are under development to ensure magnetic cleanliness will be obtained. Measurements are also planned of the inbound bow shock, the magnetosheath and the cometary ionopause. The data will be collected as close as 1000 km from the comet surface.

Neubauer, F. M.↗
NASA NTRS1979

Heating of ions to superthermal energies in the topside ionosphere by electrostatic ion cyclotron waves

The soft particle spectrometer on the Isis 2 spacecraft occasionally observes fluxes of ions moving upward out of the ionosphere in the vicinity of the auroral oval. These ion fluxes are characterized by a sharp pitch angle distribution usually peaked at an angle somewhat greater than 90 deg, indicative of particles heated to a large transverse temperature in a narrow range below the spacecraft. The observations are interpreted in terms of electrostatic ion cyclotron waves, which heat the ions to superthermal energies transverse to the earth's magnetic field. When the transverse energy increases, the repulsive force of the earth's magnetic field, proportional to the particle magnetic moment, repels the particles away from the earth.

Ungstrup, E.↗
NASA NTRS1976

Rocket-borne wave, field, and plasma observations in unstable polar cap E-region

This paper presents initial results from the first comprehensively instrumented rocket flown through a Farley-unstable polar cap E-region. Ground-based ionosondes and magnetometers at two locations and HF radar backscatter at the launch site were used to determine the presence of a geographically widespread ionospheric plasma instability. The observed wave direction, electric field, and current density fit the predictions of the linear theory of the Farley instability, whereas the gradient-drift instability seems to be excluded by the geometry of the observations.

Olesen, J. K.↗
NASA NTRS1975

Rocket-borne particle, field, and plasma observations in the cleft region

Results are reported for comprehensive observations of magnetic and electric fields together with ambient and suprathermal plasmas above the dayside auroral oval with rocket-borne instrumentation which penetrated the cleft region. Measurements were also obtained equatorward and poleward of the cleft. Convection velocities as inferred from electric-field measurements were generally toward noon equatorward of the cleft and were antisunward over the polar cap. Observations of electron temperatures, electric fields, and low-frequency electrostatic noise provide strong evidence of a plasma instability (Farley-Buneman) in the E-layer associated with the appearance of the 'slant E condition' identified in ground-acquired ionograms. The positions of these measurements relative to that of the cleft were firmly established via the determination of the plasma environment with an electrostatic analyzer.

Ungstrup, E.↗