SEARCH · Engineering Papers

Results for “MAGNETOMETERS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,621 records · Page 90

All sources NASA NTRS DOE OSTI

NASA NTRS1985

Auroral zone electric fields from DE 1 and 2 at magnetic conjunctions

Nearly simultaneous measurements of auroral zone electric fields are obtained by the Dynamics Explorer spacecraft at altitudes below 900 km and above 4,500 km during magnetic conjunctions. The measured electric fields are usually perpendicular to the magnetic field lines. The north-south meridional electric fields are projected to a common altitude by a mapping function which accounts for the convergence of the magnetic field lines. When plotted as a function of invariant latitude, graphs of the projected electric fields measured by both DE-1 and DE-2 show that the large-scale electric field is the same at both altitudes, as expected. Superimposed on the large-scale fields, however, are small-scale features with wavelengths less than 100 km which are larger in magnitude at the higher altitude. Fourier transforms of the electric fields show that the magnitudes depend on wavelength. Outside of the auroral zone the electric field spectrums are nearly identical. But within the auroral zone the high and low altitude electric fields have a ratio which increases with the reciprocal of the wavelength. The small-scale electric field variations are associated with field-aligned currents. These currents are measured with both a plasma instrument and magnetometer on DE-1.

Weimer, D. R.↗

NASA NTRS1985

Patchy reconnection and magnetic ropes in astrophysical plasmas

The formation of flux ropes in the magnetosphere of Venus due to velocity shear is examined in order to infer the properties of flux ropes in the earth magnetosphere. Observational data obtained by the International Sun-Earth Explorer (ISEE) spacecraft for the geometry of directed flows in the earth magnetosheath are compared with magnetometer measurements carried out on board Pioneer Venus Orbiter, and the results are discussed in detail. It is shown that the velocity shear is the dominant element shaping the magnetic structure of the magnetosheaths.

Russell, C. T.↗

NASA NTRS1985

Cryogenic Equivalence Principle Experiment

The purpose of this project is to test the equivalence of inertial and passive gravitational mass in an Earth-orbiting satellite. A ground-based experiment is now well developed. It consists of comparing the motions of two cylindrical test masses suspended in precision superconducting magnetic bearings and free to move along the horizontal (axis) direction. The masses are made of niobium and lead-plated aluminum. A position detector based on a SQUID magnetometer measures the differential motion between the masses. The periods of the masses are matched by adjustment of the position detector until the system is insensitive to common mode signals, and so that the experiment is less sensitive to seismic vibration. The apparatus is contained in a twelve inch helium dewar suspended in a vibration isolation stand. The stand achieves 30 db isolation from horizontal motions between 0.1 and 60 Hz, by simulating the motion of a 200 meter long pendulum with an air bearing. With this attenuation of seismic noise and a common mode rejection ratio of 10 to the 5th power in the differential mode, the ground based apparatus should have a sensitivity to equivalence principle violations of one part in 10 to the 13th power; the satellite version might have a sensitivity of one part in 10 to the 17th power.

Everitt, C. W. F.↗

NASA NTRS1985

Design of Cryocoolers for Microwatt Superconducting Devices

The primary applications of the cryocoolers are for cooling various Josephson devices such as SQUID magnetometers and amplifiers, voltage standards, and microwave mixers and detectors. The common feature of these devices is their extremely low inherent bias power requirement, of the order of 10/1 W per junction. This provides the possibility of designing compact, low-power cryocoolers for these applications. Several concepts were explored and a number of laboratory model cryocoolers were built. These include low-power nonmagnetic regenerative machines of the Stirling or Gifford-McMahon type, three or four-stage Joule-Thomson machines, liquid-helium dewars with integral small cryocoolers to reduce the evaporation rate, and liquid-helium dewars with integral continuously or intermittently operated small helium liquefiers to permit operation of cryogenic devices for indefinite time periods.

Zimmerman, J. E.↗

NASA NTRS1986

Initial results of the Global Thermospheric Mapping Study (GTMS)

The Global Thermospheric Mapping Study (GTMS) is a multi-technique experimental study of the thermosphere designed to map simultaneously its spatial and temporal morphology with a thoroughness and diversity of measurement techniques heretofore unachieved. The GTMS is designed around the Incoherent Scatter Radar Chain in the western hemisphere. The European incoherent scatter radars and the worldwide communities of Fabry-Perot interferometers, meteor wind radars, partial reflection drifts radars, MST radars, and satellite probes are included to extend the spatial coverage and types of measurements available. Theoretical and modeling support in the areas of thermospheric and ionospheric structure, tides, and electric fields are included to aid in program planning and data interpretation. Solar activity was low on the three observation days (F10.7 = 97, 98, 96) and magnetic conditions were unsettled to active (A = 10, 12, 20). All six incoherent scatter radar facilities collected data. Each collected F region data day and night while Saint Santin and Millstone Hill additionally collected E region data during daylight hours. Initial results from Sondrestrom and Millstone Hill are presented. Good quality Fabry Perot data were collected at Fritz Peak and San Jose dos Campos. Weather conditions produced poor results at Arequipa and Arecibo. Initial results from Fritz Peak are presented. Mesosphere/lower-thermosphere observations were conducted under the ATMAP organization. The magnetometer chains also were operational during this campaign. Initial thermospheric general circulation model predictions were made for assumed solar-geophysical conditions, and selected results are presented.

Oliver, W. L.↗

NASA NTRS1985

Magnetic disturbances in the vicinity of synchronous orbit and the substorm current wedge - A case study

It is pointed out that magnetospheric substorms have been referred to as the 'fundamental instability' of the magnetosphere which results from coupling between the solar wind and the earth's magnetic and plasma environment. The present paper is mainly concerned with magnetic observations made by the midlatitude Air Force Geophysics Laboratory (AFGL) Magnetometer Network, the GOES 2 and 3 synchronous satellites, and the near-geosynchronous P78-2 Spacecraft Charging at High Altitudes (SCATHA) satellite. Ground-based Pi 2 and magnetic bay observations are used to detect a clear substorm onset. An idealized model of the substorm current system is utilized to relate the observations to the spatial location and temporal development of the substorm disturbance near synchronous orbit.

Singer, H. J.↗

NASA NTRS1985

Observations of field-aligned currents at the plasma sheet boundary - An ISEE-1 and 2 survey

Using ISEE-1 and 2 magnetometer data, a survey of field-aligned currents at the boundary of the plasma sheet between 10 and 22 earth radii down the magnetotail was performed. Most cases are observed as the plasma sheet expands across the spacecraft. It is found that the currents are most often observed flowing earthward throughout this region of the tail; however, a fraction of the cases corresponds to tailward flowing currents and these tend to be found dawnward of midnight. Toward dusk no tailward currents are found. The currents at the plasma sheet boundary should map to the high latitude boundary of the auroral zone, and consequently one might expect them to have a Region 1 polarity; just the opposite is observed. Typical sheet current densities for these cases are roughly 5 mA/m.

Elphic, R. C.↗

NASA NTRS1985

Space plasma physics results from Spacelab 1

The Spacelab 1 payload carried several instrument systems which together investigated a number of space plasma phenomena. These experiments used the Space Shuttle Orbiter as a platform for making controlled particle-beam, plasma and neutral gas inputs to the ionosphere and magnetosphere and for observing the outputs produced. Spacelab 1 space-plasma investigations included the Space Experiments with Particle Accelerators (SEPAC), Phenomena Induced by Charged Particle Beams (PICPAB), Atmospheric Emissions Photometric Imaging (AEPI) and the Low Energy Electron Spectrometer and Magnetometer. Among the major phenomena investigated both singly and jointly by these experiments are vehicle charging and neutralization, beam-plasma and wave-particle interactions, anomalous ionization phenomena produced by neutral-gas and plasma injections and several phenomena induced by modulated particle beam injections.

Burch, J. L.↗

NASA NTRS1986

A multiple-satellite observation of the high-latitude auroral activity on January 11, 1983

Akasofu and Tsurutani (1984) have observed very unusual auroral activity on January 10-11, 1983. They employed visible line scan imagery from the Defense Meteorological Satellite Program (DMSP) F6 satellite to monitor auroral activity over the northern (winter) polar region. Magnetometer data from the ISEE 3 and IMP 8 spacecraft were used to monitor the interplanetary magnetic field (IMF) orientation. A number of auroral features which occurred in coincidence with changes in the IMF orientation were noted. The present paper is mainly concerned with the specific occurrence of a broad transpolar are later on January 11, 1983. During this occurrence, the IMF B(z) and B(y) components were positive and stable in time. This report has the objective to use a fortunate orbital configuration of three low-altitude polar orbiting spacecraft to probe the distribution of precipitating plasma responsible for the arc.

Gorney, D. J.↗

NASA NTRS1986

ISEE 3 observations during a plasma sheet encounter at 140 earth radii - Evidence for enhancement of reconnection at the distant neutral line

A plasma sheet encounter of the ISEE-3 spacecraft in the distant tail at 140 earth radii on March 20, 1983 is studied using magnetic field, energetic particle, and plasma electron data sets. The H-component magnetograms from auroral magnetometer stations, intensity-time profiles, high resolution magnetic field measurements, and electron and proton angular distributions are analyzed. The dynamics of the plasma sheet displayed by the strong tailward and earthward directed ion beams, large northward and southward magnetic fields excursions, and short tailward and earthward plasma flows are described.

Scholer, M.↗

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

Spatial distributions of magnetic field fluctuations in the dayside magnetosheath

In a study that tests the hypothesis that magnetosheath magnetic fields are disturbed on plasma streamlines which are connected to the quasi-parallel bow shock, magnetometer observations from the ISEE 2 and IMP 8 spacecraft are used to investigate the dayside spatial distributions of fluctuating magnetosheath fields for different interplanetary field orientations. The results suggest that although other sources such as Kelvin-Helmholtz instabilities and flux transfer processes probably contribute to the fluctuations in the magnetosheath field, the quasi-parallel shock source is an important contributor in the dayside region.

Luhmann, J. G.↗

NASA NTRS1986

The international cometary explorer mission to comet Giacobini-Zinner

The encounter, on September 11, 1985, between the International Cometary Explorer (ICE) and the comet Giacobini-Zinner, is described in detail. The primary goal of this encounter was to study the interaction between the solar wind and the comet. At the time of the encounter, the spacecraft was approximately 50 times farther from the earth than it was designed to go, making it difficult to recover data. The seven instruments on board ICE which were operational in this mission were the plasma electron, magnetometer, plasma waves, radio waves, plasma composition, low-energy cosmic ray, and energetic proton instruments. The encounter is depicted schematically, showing the times different regions were crossed. The spacecraft velocity vector, measured relative to the comet, made a 93 deg angle with respect to the plasma tail axis. The spacecraft crossed the center of the comet ion tail at approximately 1102 U.T. A cold, dense plasma was found near the center of the tail; at the very center was a temperature reading of only 13,000 K and a density of 670 electrons/cu cm. Alfven's model of comet tail formation was confirmed and it was found that water group ions are the dominant comet component. Pulses were detected which were attributed to dust particles hitting the spacecraft.

Von Rosenvinge, T. T.↗

NASA NTRS1986

International Cometary Explorer encounter with Giacobini-Zinner - Magnetic field observations

The vector helium magnetometer on the International Cometary Explorer observed the magnetic fields induced by the interaction of comet Giacobini-Zinner with the solar wind. A magnetic tail was penetrated about 7800 kilometers downstream from the comet and was found to be 10,000 kilometers wide. It consisted of two lobes, containing oppositely directed fields with strengths up to 60 nanoteslas, separated by a plasma sheet about 1000 kilometers thick containing a thin current sheet. The magnetotail was enclosed in an extended ionosheath characterized by intense hydromagnetic turbulence and interplanetary fields draped around the comet. A distant bow wave, which may or may not have been a bow shock, was observed at both edges of the ionoshpeath. Weak turbulence was observed well upstream of the bow wave.

Smith, E. J.↗

NASA NTRS1985

The International Cometary Explorer mission to comet Giacobini-Zinner

The International Cometary Explorer (ICE), scheduled to pass the tail of Comet Giacobini-Zinner on September 11, 1985, was expected to address first-order questions bout the interaction between solar wind and comets. Since ICE was not initially intended for comet studies, it did not have sun-sensitive imaging instruments designed to image the comet nucleus. In effect, ICE was free to pass through the tail of the comet. The ICE spacecraft, a 16-faceted cylindrical drum just over five ft high with a spin axis normal to the ecliptic plane, was designed to encounter the comet at a distance of 0.47 AU from the earth. Scientific instruments on board the spacecraft include: (1) the electron plasma experiment, (2) the vector helium magnetometer, (3) the plasma wave experiment, (4) the radio waves experiment, (5) the plasma ion experiment, (6) the low-energy cosmic ray experiment, and (7) the energetic protons experiment. Targeting error was expected as a result of solar-wind induced plasma tail wagging. Comet interception was planned to be at a distance of 10,000 km from the nucleus.

Von Rosenvinge, T. T.↗

NASA NTRS1985

The International Cometary Explorer (ICE) mission to comet Giacobini-Zinner (G/Z)

The primary objectives of the International Cometary Explorer (ICE) mission is to provide in situ data on the interaction between solar wind and the atmosphere of the P/Giacobini-Zinner comet (G/Z), making measurements of particles, fields, and waves while passing through the cometary tail of G/Z on September 11, 1985. Following the G/Z tail intercept, the ICE measurements will complement the later upstream measurements obtained by the Comet Halley probe. The major ICE payload includes a vector helium magnetometer, the plasma-wave experiment, the radio-wave experiment, the plasma-electron experiment, and the plasma ion experiment. Other experiments are intended to measure energetic protons, X-rays, low energy to high energy cosmic rays, cosmic ray electrons, and gamma-ray bursts. The ICE measurements of G/Z will be supplemented with ground-based measurements. Schematic diagrams are included.

Brandt, J. C.↗

NASA NTRS1986

In situ magnetic field observations of the AMPTE artificial comet

Magnetometers aboard the IRM and UKS spacecraft monitored the magnetic field during the AMPTE artificial comet experiment of Dec. 27, 1984. Rapid photoionization of the released barium vapor resulted in the formation of a magnetic cavity, shielded from the ambient magnetic field.The presence of this highly conductive obstacle caused draping and compression of the solar wind magnetic field.

Luehr, H.↗

NASA NTRS1986

Average dimension and magnetic structure of the distant Venus magnetotail

The first major statistical investigation of the far wake of an unmagnetized object embedded in the solar wind is reported. The investigation is based on Pioneer Venus Orbiter magnetometer data from 70 crossings of the Venus wake at altitudes between 5 and 11 Venus radii during reasonably steady IMF conditions. It is found that Venus has a well-developed-tail, flaring with altitude and possibly broader in the direction parallel to the IMF cross-flow component. Tail lobe field polarities and the direction of the cross-tail field are consistent with tail accretion from the solar wind. Average values for the cross-tail field (2 nT) and the distant tail flux (3 MWb) indicate that most distant tail field lines close across the center of the tail and are not rooted in the Venus ionosphere. The findings are illustrated in a three-dimensional schematic.

Saunders, M. A.↗