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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.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

The geomagnetic field at 1982 from DE-2 and other magnetic field data

Data from the DE-2 spacecraft are combined with data from the Magsat spacecraft and data from magnetic observatories and magnetic surveys to derive a geomagnetic field model for the period from May 1979 to May 1983. The model is an extension of the Goddard Space Flight Center (12/83) model. The model includes a solution for parameters representing the noncore field, or anomaly bias, at each observatory in the Project Magnet program. A table of these anomalies is presented. The results from this model are compared with those from the IGRF1980 (Peddie, 1982) and the IGRF1987 (Barraclough, 1987).

Langel, R. A.↗
NASA NTRS1971

Geomagnetic survey by the polar-Orbiting Geophysical Observatories.

Summary of reduced data from the polar Orbiting Geophysical Observatories OGO 2 and 4, spanning the time period from Oct. 14, 1965 to the end of 1967. A brief discussion of the accuracy of the observations is followed by a description of the data extent. It is shown that the quantity of data acquired by the OGO magnetometers far exceeds the total for all other magnetic survey sources. Data acquisition for only about a two-week interval gives virtually complete global coverage. Procedures and considerations underlying the data analysis performed are discussed. Suggestions for further work are presented.

Cain, J. C.↗
NASA NTRS1972

Gosses Bluff impact structure, Australia.

A comprehensive study has been carried out of the Gosses Bluff structure in Central Australia, which is a typical cryptoexplosion structure. The study included detailed geologic mapping, and seismic reflection and refraction, gravity, aeromagnetic, and ground magnetic surveys. It is concluded that the structure is an eroded crater formed by a single nearly instantaneous shock event, and that the event can be explained only by impact.

Milton, D. J.↗
NASA NTRS1974

The oceanic islands - Azores

A presentation is made of the known geological, geophysical, and geochemical data on the Azores. The regional setting of the islands is described; under the geological heading, surface geology and petrochemistry are discussed; and paleomagnetism, marine magnetic surveys, gravity, seismology, and heat flow are treated in the geophysics category. A model for the origin of the Azores is constructed on the basis of these observations.

Ridley, W. I.↗
NASA NTRS2003

Basaltic Magmatism: The Dominant Factor in the Petrologic and Tectonic Evolution of the Earth

Silicate bodies such as the Moon, Mars, probably Mercury, and possibly Venus, appear to have evolved in three main stages: a first (felsic) differentiation, a late heavy bombardment, and a second (basaltic) differentiation. It has been proposed that the Earth underwent a similar sequence. This paper argues that the second differentiation, basaltic magmatism, has dominated the petrologic and tectonic evolution of the Earth for four billion years. A global andesitic crust, formed during and after accretion of the planet, was disrupted by major impacts that triggered mantle upwelling and sea-floor spreading about 4 billion years ago. The oceanic crust collectively has since been formed by basaltic volcanism, from spreading centers and mantle plumes. However, the continental crust has also been greatly affected. Basaltic underplating has promoted anatexis and diapiric intrusion of granitoids in granite-greenstone terrains, as well as providing heat for regional metamorphism. Basaltic intrusions, such as the Nipissing diabase of the Sudbury area, have added to the thickness of continental crust. Satellite magnetic surveys suggest that there are more such basaltic intrusions than previously realized; examples include the Bangui anomaly of central Africa and the Kentucky anomaly. Basaltic overplating from mafic dike swarms has repeatedly flooded continents; had it not been for erosion, they would be covered with basalt as Venus is today. The tectonic effects of basaltic volcanism on continents have only recently been realized. The World Stress Map project has discovered that continents are under horizontal compressive stress, caused by push from mid-ocean ridges, i.e., by basaltic volcanism. The stress fields are generally uniform over large intraplate areas, and could contribute to intraplate tectonism. Seafloor spreading has demonstrably been effective for at least 200 million years, and ridge push thus a contributor to tectonic activity for that long. Collectively, the petrologic and tectonic evolution of the Earth has been dominated for about 4 billion years by the 'second differentiation,' i.e., by basaltic magmatism.

Lowman, Paul D., Jr.↗
NASA NTRS2021

A Century of Tidal Variability in the North Pacific Extracted from Hourly Geomagnetic Observatory Measurements at Honolulu

Previous analyses of hourly tide-gauge data taken at Honolulu since 1905 have shown that both sea level and the amplitude of the tides have increased synchronously over time, and a process has been proposed whereby the common cause is an increase in ocean temperature. Validation with independent data of this change in tides, as well as the proposed cause, has been lacking Ocean tides also generate magnetic fields that reach far outside the ocean, and tidal signals are clearly seen in the hourly data since 1905 from the Honolulu geomagnetic observatory. Here, it is found that the tidal amplitudes have increased synchronously in the tide-gauge and magnetic records, providing independent support for the previous results. Further information about the changing ocean is likely contained in the historical data from geomagnetic observatories as well as the global coverage of modern satellite magnetic surveys.

Robert H Tyler↗
NASA NTRS1992

Survey of transient magnetic field events in the dayside magnetosphere

Data acquired with AMPTE/CCE are employed to investigate transient magnetic field events (TMFEs) in the dayside magnetosphere. TMFEs are found to occur more frequently near the magnetopause than deep in the magnetosphere, and the amplitude of a TMFE increases as the spacecraft comes closer to the magnetopause. It is inferred that they are generated at the magnetopause. From the MLT dependence of the rotational polarity of the transverse magnetic field perturbation, it is suggested that TMFE structures move longitudinally away from the noon meridian. Latitudinal motion away from the equator is also inferred from the latitudinal dependence of the occurrence rates of the standard and reverse events. The motion of TMFEs is tailward in both azimuthal and north-south directions. It is suggested that TMFEs carry oppositely directed twin field-aligned currents, separated in the direction perpendicular to the direction of motion and having the same current intensity.

Kawano, H.↗
NASA NTRS1997

A Combined MG II/CA II Survey of Stellar Magnetic Activity in the Solar Neighborhood

We use nearly contemporaneus low-resolution IUE observations of Mg II h + k emission and Mount Wilson Observatory Ca II H + K S indices for 33 pairs of observations of lower main sequence stars to formulate a relationship that will permit accurate predictions of S values as a function of (B - V) color and Mg II h + k flux. The resulting relationship is useful because it will extend the set of solar neighborhood stars for which a uniform estimate of chromospheric activity is available to include stars that are not observable from Mount Wilson as well as providing additional estimates of activity levels for stars that are on the Mount Wilson HK Project observing list.

Wicklund, B. M.↗
NASA NTRS1981

The enigma of lunar magnetism

Current understandings of the nature and probable origin of lunar magnetism are surveyed. Results of examinations of returned lunar samples are discussed which reveal the main carrier of the observed natural remanent magnetization to be iron, occasionally alloyed with nickel and cobalt, but do not distinguish between thermoremanent and shock remanent origins, and surface magnetometer data is presented, which indicates small-scale magnetic fields with a wide range of field intensities implying localized, near-surface sources. A detailed examination is presented of orbital magnetometer and charged particle data concerning the geologic nature and origin of magnetic anomaly sources and the directional properties of the magnetization, which exhibit a random distribution except for a depletion in the north-south direction. A lunar magnetization survey with global coverage provided by a polar orbiting satellite is suggested as a means of placing stronger constraints on the origin of lunar crustal magnetization.

Hood, L. L.↗
NASA NTRS1977

On deducing the magnetization of the lunar surface from orbital surveys

A combination of orbital photographic, selenochemical, and magnetic surveys may elucidate the mechanism by which the lunar surface became magnetized and possibly yield an estimate of the intensity of the ancient magnetizing field and its time variation. The determination of the size and shape of the magnetized regions requires the measurement of the altitude dependence of field, especially at low altitudes (less than 100 km) and with a high enough sampling rate to resolve the profile at the edges of magnetized bodies. The planned Lunar Polar Orbiter may well provide the necessary data.

Russell, C. T.↗
NASA NTRS1992

Project Magnet High-level Vector Survey Data Reduction

Since 1951, the U.S. Navy, under its Project MAGNET program, has been continuously collecting vector aeromagnetic survey data to support the U.S. Defense Mapping Agency's world magnetic and charting program. During this forty-year period, a variety of survey platforms and instrumentation configurations have been used. The current Project MAGNET survey platform is a Navy Orion RP-3D aircraft which has been specially modified and specially equipped with a redundant suite of navigational positioning, attitude, and magnetic sensors. A review of the survey data collection procedures and calibration and editing techniques applied to the data generated by this suite of instrumentation will be presented. Among the topics covered will be the determination of its parameters from the low-level calibration maneuvers flown over geomagnetic observatories.

Rachel J Coleman↗
NASA NTRS1980

Magsat - A new satellite to survey the earth's magnetic field

The Magsat satellite was launched on Oct. 30, 1979 into a sun-synchronous dawn-dusk orbit, of 97 deg inclination, 350 km perigee, and 550 km apogee. It contains a precision vector magnetometer and a cesium-vapor scalar magnetometer at the end of a 6-m long graphite epoxy scissors boom. The magnetometers are accurate to 2 nanotesla. A pair of star cameras are used to define the body orientation to 10 arc sec rms. An 'attitude transfer system' measures the orientation of the magnetometer sensors relative to the star cameras to approximately 5 arc sec rms. The satellite position is determined to 70 meters rms by Doppler tracking. The overall objective is to determine each component of the earth's vector magnetic field to an accuracy of 6 nanotesla rms. The Magsat satellite gathers a complete picture of the earth's magnetic field every 12 hours. The vector components are sampled 16 times per second with a resolution of 0.5 nanotesla. The data will be used by the U.S. Geological Survey to prepare 1980 world magnetic field charts and to detect large-scale magnetic anomalies in the earth's crust for use in planning resource exploration strategy.

Mobley, F. F.↗
NASA NTRS2020

Measuring the Masses of Magnetic White Dwarfs: A NuSTAR Legacy Survey

The hard X-ray spectrum of magnetic cataclysmic variables can be modelled to provide a measurement of white dwarf mass. This method is complementary to radial velocity measurements, which depend on the (typically rather uncertain) binary inclination. Here we present results from a Legacy Survey of 19 magnetic cataclysmic variables with NuSTAR.We fit accretion column models to their 20–78 keV spectra and derive the white dwarf masses, finding a weighted average M(sub WD) = 0.77 ± 0.02 M(sub ⨀), with a standard deviation σ = 0.10 M(sub ⨀), when we include the masses derived from previous NuSTAR observations of seven additional magnetic cataclysmic variables. We find that the mass distribution of accreting magnetic white dwarfs is consistent with that of white dwarfs in non-magnetic cataclysmic variables. Both peak at a higher mass than the distributions of isolated white dwarfs and post-common-envelope binaries. We speculate as to why this might be the case, proposing that consequential angular momentum losses may play a role in accreting magnetic white dwarfs and/or that our knowledge of how the white dwarf mass changes over accretion–nova cycles may also be incomplete.

Novae↗
NASA NTRS1983

Mathematical developments regarding the general theory of the Earth magnetism

A literature survey on the Earth's magnetic field, citing the works of Gauss, Erman-Petersen, Quintus Icilius and Neumayer is presented. The general formulas for the representation of the potential and components of the Earth's magnetic force are presented. An analytical representation of magnetic condition of the Earth based on observations is also made.

Schmidt, A.↗
NASA NTRS1994

The incidence of magnetism among white dwarfs: The first stars below 100 kilogauss

A survey for magnetic fields among a magnitude-limited sample of DA white dwarfs has identified two stars with weak circular polarization features across the profiles of H(alpha) and H(beta) WD 1350-090 (LP 907-037) was found to have a disk-averaged longitudinal field component B(sub e) = +85 +/- 9 kG at one epoch, while WD 0009+501 (G 217-037) has been measured on several occasions at values between B(sub e) approximately 0 and nearly -100 kG. The latter results imply an oblique rotator with a period between 2 and 20 hr. Magnetism on white dwarfs has now been detected over more than four orders of magnitude in strength. Assuming flux conservation, the new discoveries imply organized field patterns near the end of the main-sequence phase of only approximately 10 G. However, the overall incidence of magnetism among white dwarfs remains low, with more than 90% of stars having fields below approximately 10 kG. There is tentative evidence from line profile analysis that WD 1350-090 is a high-mass object (M greater than 1 solar mass), but an accurate parallax and more thorough spectroscopic study are required.

Schmidt, Gary D.↗
NASA NTRS1975

A survey of the interplanetary magnetic field

All interplanetary magnetic field measurements from near-earth satellites have been collected in the form of hourly averages for the years 1963-1974. Solar cycle variations of the field and the exceptional events of this cycle are discussed in relation to the associated cosmic ray events, and statistical properties of the field over this period are presented. The presence of magnetic blobs as a permanent feature of the field is demonstrated and explained. The implications of these results for the theory of cosmic ray modulation are presented and analyzed.

Barouch, E.↗