Engineering Papers⌕ Search

Engineering topics

Arnoldy, R. L.

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

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Rocket study of auroral processes

Abstracts are presented of previously published reports analyzing data from three Echo 3 rocket flights. Particle experiments designed for the Terrier-Malmute flight, the Echo 5 flight, and the Norwegian Corbier Ferdinand 50 flight are described and their flight performance evaluated. Theoretical studies on auroral particle precipitation are reviewed according to observations made in three regions of space: (1) the region accessible to rockets and low altitude satellites (few hundred to a few thousand kilometers); (2) the region extending from 4000 to 8000 km (S3-3 satellite range); and (3) near the equatorial plane (geosynchronous satellite measurements). Questions raised about auroral arc formation are considered.

Arnoldy, R. L.↗
NASA NTRS1981

The hot plasma environment and floating potentials of an electron-beam-emitting rocket in the ionosphere

The plasma environment surrounding the Echo III accelerator payload is examined with an extensive array of particle sensors. Suprathermal electrons are produced isotropically around the payload during the gun firings and decay away in approximately 32 ms. The largest directional intensities of this component are observed at the higher altitudes. Quick echo electrons are also observed to produce suprathermal electrons when they encounter the payload. The hot electrons surrounding the accelerator payload during gun injections bring sufficient charge to the payload to neutralize it provided the loss of charge by secondary production on the payload skin is small. Since the hot population exists for tens of milliseconds after the gun turnoff, it results in driving the payload up to 4 volts negative during this time. Quick echo electrons creating suprathermal electrons around the payload also drive the payload to a few volts negative.

Arnoldy, R. L.↗
NASA NTRS1981

Review of auroral particle precipitation

An attempt to establish the precipitation signal of an auroral arc based on data gathered by sounding rockets and satellites is presented. Rocket sounding is useful for altitudes up to a few thousand km, the S3-3 satellite from 4000-8000 km, and satellites in GEO for the equatorial plane. Inverted V structures have been observed down to a few km in width by rockets, and occur on open as well as closed field lines. Observations of bursts of field-aligned electrons, simultaneous ion and electron precipitation, counter-streaming electrons and conics have been interpreted as indicating ac phenomena. The S3-3 has recorded the presence of upward flowing ions, beams, and conics, downward flowing ions, and counter-streaming electrons in the 4000-8000 km region. Finally, plasma injections at synchronous orbit have been identified as the equatorial plane signature of any auroral substorm.

Arnoldy, R. L.↗
NASA NTRS1980

The dawn polar cap boundary at high altitude

A plasma decrease event has been observed in the dawn sector during large magnetic storms. Supporting plasma data from ATS-6 and GEOS-1 satellites are used to argue that this type of decrease is similar to the midnight-sector plasma-sheet boundary crossing. Implications of such a boundary crossing near dawn for the storm time magnetic field are discussed.

Moore, T. E.↗
NASA NTRS1980

Coincident particle observations from AE-C and ATS 6 during the October 28, 1977, geomagnetic storm

Simultaneous measurements of ion and electron energy spectra recorded during the October 28, 1977 geomagnetic storm by the AE-C and ATS 6 spacecraft when both were nearly on the same L shell are evaluated and compared. The orbit of the AE-C generates wide longitudinal coverage of the auroral oval, whereas the ATS 6, which is located at geosynchronous orbit, samples the equatorial particle population. It is shown that the coincident electron energy spectra obtained by the two satellites agree well above 5 keV and the spectra of electrons peak near 1 keV at ionospheric altitudes, while no peaks in energy appear at synchronous altitude.

Zanetti, L. J.↗
NASA NTRS1980

Rocket observations at the northern edge of the eastward electrojet

The paper discusses a Nike-Tomahawk rocket launched north over quiet, late evening auroral arcs in March 1975. A northward magnetic disturbance was observed on the ground under the rocket trajectory; south of the arcs the northward electric field was 60 mV/m, indicating strong westward plasma flow. An eastward electrojet current layer was penetrated in the upward flight, and precipitating electrons were observed over each arc. Using the observed electron flux and a model of the ionosphere, the Hall and Pedersen conductivities were calculated which were used to compute the eastward and northward components of the horizontal ionospheric currents. The joule power decreased abruptly in the auroral arcs, as the precipitating electron power increased; the total dissipated power was the same inside the arcs, between them and southward. North of the aurora the electric field and dissipated power remained low; field-aligned currents carried by the observed electrons were about a factor of 3 lower than those inferred from the magnetic field measurements.

Cahill, L. J., Jr.↗
NASA NTRS1980

Comparative rocket observations of ionospheric electric fields in the auroral oval

The ion drift technique of measuring ionospheric electric fields is compared to two other simultaneous measurements. Rocket measurements in the evening auroral oval are checked against a dual probe, also in situ, and the ground based STARE auroral radar. The technique is explained thoroughly as well as tested for its dependence on mass. Two evening auroral oval conditions were observed from Andoya, Norway in January and February 1977. The first flight, 18:1005, measured electric fields over a quiet pre-midnight discrete arc. An interesting plasma convection reversal was observed poleward of the arc. The subsequent 18:1004, samples a breakup phase aurora nearer local midnight.

Zanetti, L. J., Jr.↗
NASA NTRS1978

Auroral electron distribution function

During a rocket flight over an active aurora, electron velocity distribution is studied in the 15-25 keV range. The results are then compared to optical observations made by all-sky cameras and a television system. A broad plateau produced by downcoming electrons was observed. Smaller plateaus were seen when the rocket was south of arcs evident in all-sky camera photographs. By extending to higher energies when the rocket passed out of auroral forms, the plateaus appeared to broaden. When the rocket left an arc or entered weak diffuse auroral structures, the plateaus shrank as the more energetic portions faded. When field-aligned rays were observed within the arcs, the plateau's high-velocity cutoff was found to fluctuate. The results indicate that the auroral plasma was very unstable above the rocket. It is suggested that plateaus are produced as an unstable plasma evolves toward a quasi-equilibrium state.

Kaufmann, R. L.↗
NASA NTRS1978

Investigation of electrical currents in the auroral ionosphere

Two papers are presented on the investigation of electrical currents in the auroral ionosphere: (1) The Relationship Between Field-Aligned Current Carried by Suprathermal Electrons, and the Auroral Arc; and (2) Ionospheric Electrical Currents in the Late Evening Plasma Flow Reversal. In the first paper (1), data from four auroral sounding rockets, which directly measured field-aligned currents with partical detectors, are presented. In the second paper (2), data are presented for an instrumented sounding rocket that was launched from Andoya, Norway in January 1977, in the late evening auroral oval.

Arnoldy, R. L.↗
NASA NTRS1977

Correlation of ground-based and topside photometric observations with auroral electron spectra measurements at rocket altitudes

Data are collected by electron detectors aboard a sounding rocket measuring the primary electron spectrum and the energy flux on the field lines containing auroral light in the E region. These data are compared to calculations based on spectroscopic measurements of the auroral lines 4278, 5577, and 6300 A used in predicting the energy influx and the characteristic energy of an assumed Maxwellian primary electron spectrum for two auroral displays. Data were also collected by photometers sampling the auroral light from the E region magnetically conjugate to the rocket. These data are compared to those of current ionospheric models.

Arnoldy, R. L.↗
NASA NTRS1977

The relationship between field-aligned current, carried by suprathermal electrons, and the auroral arc

Data from four auroral sounding rockets, which directly measured field-aligned currents with particle detectors, are presented. The largest fraction of the field-aligned current carried by electrons was (1) due to precipitating electrons of energy less than 1 keV; (2) located spatially at the edges of the auroral luminosity. A model is suggested in which these currents couple the ionosphere to the magnetosphere and produce the pre-breakup auroral arc.

Arnoldy, R. L.↗
NASA NTRS1976

Acceleration of auroral electrons in parallel electric fields

Rocket observations of auroral electrons are compared with the predictions of a number of theoretical acceleration mechanisms that involve an electric field parallel to the earth's magnetic field. The theoretical models are discussed in terms of required plasma sources, the location of the acceleration region, and properties of necessary wave-particle scattering mechanisms. We have been unable to find any steady state scatter-free electric field configuration that predicts electron flux distributions in agreement with the observations. The addition of a fluctuating electric field or wave-particle scattering several thousand kilometers above the rocket can modify the theoretical flux distributions so that they agree with measurements. The presence of very narrow energy peaks in the flux contours implies a characteristic temperature of several tens of electron volts or less for the source of field-aligned auroral electrons and a temperature of several hundred electron volts or less for the relatively isotropic 'monoenergetic' auroral electrons. The temperature of the field-aligned electrons is more representative of the magnetosheath or possibly the ionosphere as a source region than of the plasma sheet.

Kaufmann, R. L.↗
NASA NTRS1975

Echo 2 - Observations at Fort Churchill of a 4-keV peak in low-level electron precipitation

The Echo 2 rocket flight launched from Fort Churchill, Manitoba, offered the opportunity to observe high-latitude low-level electron precipitation during quiet magnetic conditions. Although no visual aurora was evident at the time of the flight, an auroral spectrum sharply peaked at a few keV was observed to have intensities from 1 to 2 orders of magnitude lower than peaked spectra typically associated with bright auroral forms. There is a growing body of evidence that relates peaked electron spectra to discrete aurora. The Echo 2 observations show that whatever the mechanism for peaking the electron spectrum in and above discrete forms, it operates over a range of precipitation intensities covering nearly 3 orders of magnitude down to subvisual or near subvisual events.

Arnoldy, R. L.↗
NASA NTRS1974

Field-aligned auroral electron fluxes

Out of a series of five auroral sounding rocket flights, electron fluxes in three of the flights were observed to be sharply field-aligned. The electrons were detected with an array of electrostatic analyzers making 50-point spectral samples from 0 to 15 keV. The field-aligned fluxes resulted in a peak in the spectrum at a lower energy than that of another monoenergetic peak in the spectrum seen consistently when it was conjugate to bright auroral forms giving multiply peaked spectra. The field-aligned peak in the spectrum is apparently a phenomenon distinct from the isotropic peak and was observed to occur at various times in the energy range from a few hundred electron volts to 5 keV. The field-aligned electrons were highly collimated, having pitch angles less than 20 deg and at times less than 10 deg. The high degree of field alignment and the monoenergetic character support the model that these events can be attributed to relatively cool plasma falling through an electric potential at altitudes not too far removed from the rocket.

Arnoldy, R. L.↗