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Results for “MAGNETIC EFFECT”

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Shock induced magnetic effects in fine particle iron dispersions

Magnetic effects associated with shock induced transformation of fcc antiferromagnetic iron precipitates in polycrystalline copper disks at levels up to 5 GPa in weak magnetic fields (H not greater than 0.5 Oe) were investigated. The demagnetization and anisotropy associated with second order transition, the effects of plastic deformation in imparting magnetic anisotropy and magnetic hardening, and the influence of post shock thermal transients on magnetization associated with recovery, recrystallization and grain growth were studied. It was found that on the microsecond time scale of the shock induced first order transformation, the field sense is recorded in the transformed iron particles. For a given particle size the degree of transformation of fcc iron depends on the level of the shock. For a given shock level the resultant magnetic properties depend on the particle size distribution, with maximum effects noted in specimens with 400 to 600 A particles.

Wasilewski, P. J.↗
NASA NTRS1991

Magnetic effects of large-scale impacts on airless planetary bodies

The analysis of lunar orbital and sample data combined with laboratory measurements of impact-produced plasmas suggest that large-scale impacts on planetary surfaces may have had significant magnetic effects. These effects may potentially explain part of all lunar crustal magnetization and, by extension, may be responsible for producing paleomagnetism on other airless silicate bodies in the solar system. Theoretical studies are presented of the magnetic field and remanent magnetization effects of basin-scale impacts on the Moon. The specific case of a Moon exposed to the solar wind plasma flow and its embedded magnetic field is investigated. It is shown that maximum compressed field amplitudes occur antipodal to the impact point in agreement with the observed tendency for orbital magnetic anomalies to be concentrated antipodal to young large lunar basins. Generalization of these results to include magnetic effects of impacts on other airless or nearly airless bodies in the solar system is presented.

Hood, L. L.↗
NASA NTRS1976

Magnetic effects of shock and their implications for lunar magnetism. II

Synthetic breccias were produced by hypervelocity impact of projectiles on basalt powders in order to study the magnetization acquired during shock lithification of soil. It was found that some of the lithified products record the field at the point where they land, while others carry the original primary remanence. Even those rocks recording the direction of the ambient field did not always faithfully record the intensity of the field. When rocks were exposed to shock, it was found that the magnetic hardness of a rock has a profound effect on its magnetic response. Shock effects are seen at shock levels of less than 10 kbar, which suggests that lunar samples may have been shock-demagnetized.

Cisowski, S. M.↗
NASA NTRS1975

Magnetic effects of shock and their implications for magnetism of lunar samples

The principal problem in lunar magnetism is to account for the surprisingly large magnitude of the remanent magnetism of lunar surface material. Experiments conducted in this connection have shown that shock is an important mechanism of both magnetization and demagnetization. A description is presented of new experimental results in the low-shock range. An attempt is made to assess the effect of shock upon estimates of the ancient lunar field intensity. The results are used as a basis for a reconsideration of the present lunar field models in the light of intensity estimates and other new results. It is found that the central questions in lunar magnetism have not yet been answered to everyone's satisfaction.

Cisowski, S. M.↗
NASA NTRS1985

Magnetic Effects in the Heating and Modification of Flows in the Outer Stellar Atmospheres with Application to Early Type Star Case

Possible magnetic effects in the heating and modification of flows in early type star atmospheres are discussed by referring to the physically related phenomena dealt with for late type stars, young stars, and close binary systems. It is pointed out as the result of that the magnetic field may play important roles also in early type star atmospheres in converting the energy of the radiatively driven outflow into heat, or in modifying the outflow by nozzling or by initial modification of temperature and/or momentum by which the effect of the radiation pressure may be made the most of in accelerating the outflow.

Uchida, Y.↗
NASA NTRS1979

The magnetic effects of brecciation and shock in meteorites. II - The ureilites and evidence for strong nebular magnetic fields. III - The achondrites

Magnetic studies were conducted on samples of the ureilitic meteorites Goalpara, Havero, Novo Urei, and Kenna. Measurements included bulk magnetic susceptibility, natural remanent magnetization (NRM), saturation remanence, and the demagnetization behavior of NRM and saturation remanence. An approximate 'fossil' magnetic field intensity was determined by analysis of coercivity spectra of NRM and saturation remanence after reheating. It was found that the magnetic susceptibility of ureilites increased with severity of shock, and the NRM intensity decreases while its coercivity spectrum generally hardens with increasing shock. Goalpara and Kenna are distinguished by unexpectedly homogeneous, strong, stable, and directionally clustered NRM, indicative of a unique original magnetizing event. The results support the assertion that both ureilites and carbonaceous chondrites have formed from related nebular material and provide further evidence for a strong external magnetic field during the accretional stages and throughout an early bombardment stage.

Brecher, A.↗
NASA NTRS1972

Magnetic effect on dancing bees

Bee sensitivity to the earth's magnetic field is studied. Data cover sensitivity range and the use of magnetoreception for orientation purposes. Experimental results indicate bee orientation is aided by gravity fields when the magnetic field is compensated.

Lindauer, M.↗
NASA NTRS1977

The magnetic effects of brecciation and shock in meteorites. I - The LL-chondrites

The magnetic behavior of eight LL chondrites is analyzed in detail, and some implications for their modes of formation and evolutionary history are examined. Petrographic features of the specimens are described, and their initial magnetic characteristics are discussed. The demagnetization behavior of the initial magnetization is investigated along with the saturation remanence behavior and paleomagnetic-field intensities. The results indicate that a magnetic field of 0.01 to 0.1 Oe may have been present during postimpact cooling and that severe shock metamorphism may have given rise to the observed magnetic moments and behavior, even in the absence of ambient magnetic fields.

Brecher, A.↗