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NASA NTRS2014

Challenges in Measuring External Currents Driven by the Solar Wind-Magnetosphere Interaction

In studying the Earth's geomagnetism, it has always been a challenge to separate magnetic fields from external currents originating from the ionosphere and magnetosphere. While the internal magnetic field changes very slowly in time scales of years and more, the ionospheric and magnetospheric current systems driven by the solar wind -magnetosphere interaction are very dynamic. They are intimately controlled by the ionospheric electrodynamics and ionospheremagnetosphere coupling. Single spacecraft observations are not able to separate their spatial and temporal variations, and thus to accurately describe their configurations. To characterize and understand the external currents, satellite observations require both good spatial and temporal resolutions. This paper reviews our observations of the external currents from two recent LEO satellite missions: Space Technology 5 (ST-5), NASA's first three-satellite constellation mission in LEO polar orbit, and Communications/Navigation Outage Forecasting System (C/NOFS), an equatorial satellite developed by US Air Force Research Laboratory. We present recommendations for future geomagnetism missions based on these observations.

WIND-MAGNETOSPHERE↗
NASA NTRS2005

Magnetoresistive Flux Focusing Eddy Current Flaw Detection

A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil s longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multi-layer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

Russell A Wincheski↗
NASA NTRS2005

Magnetoresistive flux focusing eddy current flaw detection

A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil's longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multilayer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

Wincheski, Russell A.↗
NASA NTRS1972

Temperature-time relationships from lunar two phase metallic particles /14310, 14163, 14003/.

Electron-microprobe and metallographic techniques are applied in an analysis of individual phases in two-phase metallic alpha + gamma particles and phosphide-metal particles separated magnetically or mechanically from three lunar soil samples. The interface equilibrium temperatures of the two-phase particles during their lunar residence are inferred from experimental Fe-Ni and Fe-Ni-P equilibrium diagrams. Times of equilibration are determined in some cases.

Axon, H. J.↗
NASA NTRS1972

Metallic particles in the Apollo 14 lunar soil.

The metallographic structures, silicate associations and bulk compositions (Ni, Co, P, S, and Si) were determined by microprobe analysis for 205 metal particles selected by magnetic separation from the less than 1 mm, greater than 125 micron fraction of soil samples 14003,18 and 14163,165. A small number of exotic particles were encountered but almost all the metal could be accommodated within one of four subpopulations, the characteristics and genetic significance of which may be stated as follows: (1) the major proportion has Ni and Co contents corresponding to the range of meteoritic metal; (2) small proportion (about 5%) that not only has meteoritic contents of Ni and Co but also shows still distinguishable indications of meteoritic microstructure; (3) another small population (about 10%) consists of metal excavated from lunar mare basalts by cratering events, and thrown onto the Apollo 14 site; and (4) metallic spheroids (about 5%), analogous to those encountered in the vicinity of the Barringer Meteorite Crater, Arizona.

Goldstein, J. I.↗
NASA NTRS1973

Characterization of fines from the Apollo 16 site

We describe the characteristics of Apollo 16 fines samples 61281,8; 65701,13; 66031,6; 67701,26; and 67712,16 observed microscopically during the course of size and magnetic separations. Sample 67712,16 is unique in that almost all grains are rounded and no glass welded aggregates are present. All samples except 67712,16 contained about 0.5 wt.% of metal fragments 45 microns or more in diameter including occasional spheres and large single crystals. Some of this metal showed rust spots. Moessbauer spectra showed all the samples to be high in olivine compared to samples from other Apollo sites and to vary significantly in modal composition from each other. The fine grained Fe metal content and the excess absorption area near zero velocity in the Moessbauer spectra both vary with particle size and regolith maturity in the way one would predict from our model of Fe metal reduction and agglomeration during glass aggregate formation.

Housley, R. M.↗
NASA NTRS1975

Effects of maturation on the reflectance of the lunar regolith: Apollo 16 - A case study

Soils at the Apollo 16 site become progressively darker as the percentage of glassy agglutinates increases. Magnetic separates of the agglutinate fraction of a soil are always darker than the bulk soil and are darker than the nonagglutinate fraction consisting of rock and mineral fragments. Darkening of a soil with maturity is due mainly to the increasing proportion of agglutinates. Coating of rock and mineral fragments with thin deposits of glass aids darkening in a minor way, but most of these particles eventually are destroyed by melting as the soils mature.

Adams, J. B.↗
NASA NTRS1977

Grain size, petrographic, and FMR studies of the double core 60009/10 - A study of soil evolution

Six samples from the upper core 60010 of the double drive core 60009/60010 were analyzed for grain size distribution, petrographic particle types and abundances, magnetic fraction, and ferromagnetic resonance. It was found that the magnetic fraction of these soils is not equivalent to the agglutinate fraction, and magnetic separation partitions high-FeO agglutinate from low-FeO agglutinates. Various maturity indices are in essential agreement. The deposition of most or all of the core could have occurred in a single event. If that is the case, the core units have no time-stratigraphic significance and do not reflect individual cratering events.

Mckay, D. S.↗
NASA NTRS1979

Mining and beneficiation of lunar ores

The beneficiation of lunar plagioclase and ilmenite ores to feedstock grade permits a rapid growth of the space manufacturing economy by maximizing the production rate of metals and oxygen. A beneficiation scheme based on electrostatic and magnetic separation is preferred over conventional schemes, but such a scheme cannot be completely modeled because beneficiation processes are empirical and because some properties of lunar minerals have not been measured. To meet anticipated shipping and processing needs, the peak lunar mining rate will exceed 1000 tons/hr by the fifth year of operation. Such capabilities will be best obtained by automated mining vehicles and conveyor systems rather than trucks. It may be possible to extract about 40 kg of volatiles (60 percent H2O) by thermally processing the less than 20 micron ilmenite concentrate extracted from 130 tons of ilmenite ore. A thermodynamic analysis of an extraction process is presented.

Bunch, T. E.↗
NASA NTRS1979

Mesosiderites and howardites - Igneous formation and possible genetic relationships

Neutron activation data are presented for major, minor, and trace elements in whole rock howardites and silicates from mesosiderites. Compositions of howardites and mesosiderites are similar and intermediate between those of eucrites and diogenites. It is indicated that mesosiderites have a higher normative silica component than howardites. It appears that this results partly from a higher content of a highly evolved igneous component and partly from in situ reduction of FeO to Fe followed by magnetic separation of metal prior to analysis. It is shown that light rare earth elements are enriched in some mesosiderites.

Mittlefehldt, D. W.↗
NASA NTRS1983

Purely coronal flare-like variations

Quasiperiodic X-ray, UV, microwave, and metric-wave variations after a solar flare on November 6, 1980 are reported and analyzed, based on observational data from SMM (HXRBS, UVSP, HXIS), GOES-2, the 100-m radiotelescope at Bonn, and the Nancay radioheliograph. The maxima of the 13 brightenings observed are listed and characterized; a comparison is made with a 'normal' flare at 17:26 UT on the same day. The HXIS and UVSP data are discussed in terms of the physical properties, X-ray flux, O V flux, and H-alpha flux. The variations are found to be mainly thermal and purely coronal, with no chromospheric (H-alpha) participation (in contrast to the 17:26 flare). Since strong X-ray emissions were observed which should have involved the chromosphere through magnetic-field-line heat conduction, it is proposed that the variations wre produced ina coronal plasmoid magnetically separate from the chromosphere. A mechanism for the evolution of such a plasmoid from the upper loops of a giant X-ray arch is discussed. An iterative HXIS-image-deconvolution process is presented in an appendix.

Svestka, Z.↗
NASA NTRS1983

Mn-53 profiles in four Apollo surface cores

Mn-53 data are presented for four Apollo cores with an emphasis on the past 10-to-the-7th-year history of these samples: (1) Core 15011 has excess Mn-53 down to a depth of at least 9 cm, which is probably due to the continuous addition of near-surface irradiated material. (2) The Mn-53 profile for 64002 above 12 cm is relatively flat and in excess of that calculated for a static core, which suggests that the upper part of this core was deposited rapidly about 2 m.y. ago. (3) Results for the Apollo 17 drill stem show a large excess of Mn-53 from at least 3 cm downwards. Some magnetic separates obtained from this core have very high Mn-53 activities, probably due to the presence of agglutinates that were recently irradiated very near the surface. (4) The Mn-53 content of the upper part of 74002 is similar to that of trench samples collected nearby and indicates that the gray, orange, and black soils at this site have been exposed together near the surface for at least the last 10 m.y.

Nishiizumi, K.↗
NASA NTRS1986

Solar wind helium, neon and argon released by oxidation of metal grains from the Weston chondrite

A set of experiments were carried out to test the feasibility of determining unfractionated elemental and isotopic ratios for the noble gases in the presumably ancient solar wind present in the gas rich meteorites. The problems of diffusive loss was avoided by analyzing metal rather than the usual silicates. In order to avoid chemical, and even harsh physical, treatment of the sample, which might have affected the surfaces of metal grains, a means of analyzing the metal in the presence of residual silicate not removed by gentle crushing and magnetic separation was devised. Preliminary results given were obtained by taking advantage of the differing properties of metal and silicates with regard to diffusion. The results suggests that, with some modifications in the choice of pyrolysis and combustion temperatures and in the amount of O2 used, it should be possible, by oxidizing the surfaces of metal grains from gas rich meteorites, to obtain data on solar wind that has not been fractionated by diffusive loss.

Becker, R. H.↗
NASA NTRS1988

Solar, planetary, and other inert gases in two sieve fractions of a disaggregated Allende sample - A study by stepwise heating extraction

Inert gases released by stepwise heating of unaltered, strongly magnetic, and weakly magnetic samples from the 0-64 micron and the 105-250 micron fractions of a disaggregated and sieved sample of the Allende meteorite reveal the occurrence of both solar and planetary neon. The origin of the solar neon is thought to be implantation of solar wind ions. The origin of the planetary neon remains unresolved. Heavy isotope enriched components of krypton and xenon have been detected and there are some indications that a light krypton component may also be present. Other than a larger concentration of Xe-129 in the weakly magnetic samples, the signatures of the magnetic separates are isotopically very similar.

Palma, R. L.↗
NASA NTRS1989

Cometary plasma boundaries

The solar wind starts to interact with comets at distances from the nucleus of several million kilometers. The nature of the interaction changes as a function of cometocentric distance. Several dynamically important boundaries have been observed in the cometary plasma environment by instruments on several spacecraft: (1) the bow shock marks the transition from supersonic to subsonic solar wind flow, (2) the cometopause was observed at a distance of about 100,000 km from Comet Halley where the flow begins to stagnate and where charge exchange with neutrals becomes important, (3) the diamagnetic cavity boundary (i.e., contact surface, ionopause) separates magnetized and unmagnetized cometary plasma, (4) the magnetotail boundary defines the tail lobes, (5) the plasma sheet boundary defines the extent of the plasma sheet, and (6) the density enhancement layer was observed at a distance of 10,000 km from Comet Halley and might be located where the neutrals and plasma thermally decouple.

Cravens, T. E.↗
NASA NTRS1989

Products from lunar anorthite

Lunar anorthositic soil can be processed to produce oxygen, silicon, aluminum, and calcium. A process scheme starting with the beneficiation of the ore by magnetic separation and yielding the pure products is being developed. Simplifications in the process are possible if requirements regarding product purity and separation may be relaxed.

Anthony, Donald L.↗
NASA NTRS1991

Beneficiation of lunar ilmenite

One of the most important commodities lacking in the moon is free oxygen which is required for life and used extensively for propellent. Free oxygen, however, can be obtained by liberating it from the oxides and silicates that form the lunar rocks and regolith. Ilmenite (FeTiO3) is considered one of the leading candidates for production of oxygen because it can be reduced with a reasonable amount of energy and it is an abundant mineral in the lunar regolith and many mare basalts. In order to obtain oxygen from ilmenite, a method must be developed to beneficiate ilmenite from lunar material. Two possible techniques are electrostatic or magnetic methods. Both methods have complications because lunar ilmenite completely lacks Fe(3+). Magnetic methods were tested on eucrite meteorites, which are a good chemical simulant for low Ti mare basalts. The ilmenite yields in the experiments were always very low and the eucrite had to be crushed to xxxx. These data suggest that magnetic separation of ilmenite from fine grain lunar basalts would not be cost effective. Presently, experiments are being performed with electrostatic separators, and lunar regolith is being waited for so that simulants do not have to be employed.

Ruiz, Joaquin↗