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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Advanced Magnetic Materials Methods and Numerical Models for Fluidization in Microgravity and Hypogravity

To support long-duration manned missions in space such as a permanent lunar base, Mars transit, or Mars Surface Mission, improved methods for the treatment of solid wastes, particularly methods that recover valuable resources, are needed. The ability to operate under microgravity and hypogravity conditions is essential to meet this objective. The utilization of magnetic forces to manipulate granular magnetic media has provided the means to treat solid wastes under variable gravity conditions by filtration using a consolidated magnetic media bed followed by thermal processing of the solid wastes in a fluidized bed reactor. Non-uniform magnetic fields will produce a magnetic field gradient in a bed of magnetically susceptible media toward the distributor plate of a fluidized bed reactor. A correctly oriented magnetic field gradient will generate a downward direct force on magnetic media that can substitute for gravitational force in microgravity, or which may augment low levels of gravity, such as on the Moon or Mars. This approach is termed Gradient Magnetically Assisted Fluidization (G-MAFB), in which the magnitude of the force on the fluidized media depends upon the intensity of the magnetic field (H), the intensity of the field gradient (dH/dz), and the magnetic susceptibility of the media. Fluidized beds based on the G-MAFB process can operate in any gravitational environment by tuning the magnetic field appropriately. Magnetic materials and methods have been developed that enable G-MAFB operation under variable gravity conditions.

Atwater, James↗
NASA NTRS1973

Access of solar protons to the earth's polar caps.

Energetic solar proton observations in the interplanetary medium by Explorer 33 and Explorer 35 and over the polar caps by Injun 5 during the period from September 1968 through March 1970 have been examined in detail. The solar proton intensities observed over the polar regions were compared with the interplanetary intensities on an absolute basis. The high polar latitude (HPL) proton intensities tracked the magnetic field aligned interplanetary intensities well (solar-antisolar intensities as determined from the sectored Explorer data). The tracking was in agreement with the open magnetosphere model about 90% of the time - i.e., the intensities observed on the HPL magnetic lines of force, which would be connected to magnetic lines of force from the sun in an interconnected geomagnetic and interplanetary magnetic field, were in agreement with the maximum intensity of the interplanetary proton pitch angle distribution. The intensities observed at the HPL region of the opposite polar cap were in agreement with the minimum intensity of the interplanetary pitch angle distribution. The low polar latitude intensities generally tracked the maximum interplanetary intensity very well.

Fennell, J. F.↗
NASA NTRS1965

Proceedings of the Magnetics Workshop

Conference on measurement and reduction of spacecraft magnetic fields - materials and design criteria - magnetic decontamination of components - testing facilities and human tests

CONFERENCE↗
NASA NTRS1993

Cosmic ray modulation and the distant heliospheric magnetic field - Voyager 1 and 2 observations from 1986 to 1989

The relation between the cosmic ray (CR) intensity and the magnetic field strength observed by Voyager 1 and 2 during the period from 1986 through most of 1989 beyond 19 AU is examined. It is shown that these observations generally confirm the relation between changes in the CR intensity and the magnetic field intensity observed beyond 10 AU from 1981 to 1985. The CR intensity decreases when merged interaction regions (MIRs) are strong and dominating, and it fluctuates about a plateau when the effects of corotating MIRs are balanced by rarefaction regions. The CR intensity increases when the MIRs are weak and the magnetic field strength is relatively low.

Burlaga, L. F.↗
NASA NTRS1984

SMM/UVSP observations of the distribution of transition region oscillations and other properties in a sunspot

Observations of a sunspot in the C IV line at 1548 A formed in the transition region have been analyzed to obtain the time variations and/or mean values of the velocity, intensity, longitudinal magnetic field, and line width. Oscillations with periods between approximately 110 and 200 s are observed only over the umbra where the transition region magnetic field is highest and the line width is smallest. When periodic intensity variations occur at the same frequency as the velocity oscillations, the peak intensities occur slightly before the maximum upward motions. No periodic variations in the transition region magnetic field have been detected. Scatter diagrams are presented which show possible relationships between the flow velocity, emission line intensity, line width, and transition region magnetic field.

Henze, W.↗
NASA NTRS1990

Intense ionospheric electric and magnetic field pulses generated by lightning

Electric and magnetic field measurements have been made in the ionosphere over an active thunderstorm and an optical detector onboard the same rocket yielded an excellent time base for the study of waves radiated into space from the discharge. In addition to detection of intense, but generally well understood whistler mode waves, very unusual electric and magnetic field pulses preceded the 1-10 kHz component of the radiated signal. These pulses lasted several ms and had a significant electric field component parallel to the magnetic field. No known propagating wave mode has this polarization nor a signal propagation velocity as high as those measured here. This study investigated and rejected an explanation based on an anomalous skin depth effect. Although only a hypothesis at this time, a more promising explanation involving the generation of the pulse via a nonlinear decay of whistler mode waves in the frequency range 10-80 kHz is being investigated.

Kelley, M. C.↗
NASA NTRS1978

Magnetic field in the primitive solar nebula

Carbonaceous chondrites have apparently been magnetized in their early history in magnetic fields with intensities of 0.1 to 10 G, but the origin of the magnetizing field has remained obscured. It is suggested that the magnetic field recorded in the remanence of carbonaceous chondrites may have been produced by a self-excited hydromagnetic dynamo in the gaseous preplanetary nebula from which the solar system is thought to have formed. Recently computed models for the evolution of the preplanetary nebula, consisting of turbulent and differentially rotating gaseous disks with characteristic radial scales of several AU, are used to demonstrate the feasibility of this hypothesis. The maximum field intensity that might be realized by the dynamo production process is estimated to be as high as 1 to 10 G, taking into account two dynamical mechanisms that limit the strength of the field (the Coriolis force and ambipolar diffusion).

Levy, E. H.↗
NASA NTRS2005

The Distribution of Cloud to Ground Lightning Strike Intensities and Associated Magnetic Inductance Fields Near the Kennedy Space Center

Lightning strike location and peak current are monitored operationally in the Kennedy Space Center (KSC) Cape Canaveral Air Force Station (CCAFS) area by the Cloud to Ground Lightning Surveillance System (CGLSS). The present study compiles ten years worth of CGLSS data into a database of near strikes. Using shuffle launch platform LP39A as a convenient central point, all strikes recorded within a 20-mile radius for the period of record O R ) from January 1, 1993 to December 31,2002 were included in the subset database. Histograms and cumulative probability curves are produced for both strike intensity (peak current, in kA) and the corresponding magnetic inductance fields (in A/m). Results for the full POR have application to launch operations lightning monitoring and post-strike test procedures.

Burns, Lee↗
NASA NTRS1979

Solar cycle variations in IMF intensity

Annual averages of logarithms of hourly interplanetary magnetic field (IMF) intensities, obtained from geocentric spacecraft between November 1963 and December 1977, reveal the following solar cycle variation. For 2-3 years at each solar minimum period, the IMF intensity is depressed by 10-15% relative to its mean value realized during a broad 9-year period centered at solar maximum. No systematic variations occur during this 9-year period. The solar minimum decrease, although small in relation to variations in some other solar wind parameters, is both statistically and physically significant.

King, J. H.↗
NASA NTRS2003

Characteristics of Mini-Magnetospheres Formed by Paleo-Magnetic Fields of Mars

The intensely and non-uniformly magnetized crustal sources generate an effective large-scale magnetic field. In the Southern hemisphere the strongest crustal fields lead to the formation of large-scale mini-magnetospheres. In the Northern hemisphere, the crustal fields are rather weak and there are only isolated mini-magnetospheres. Re-connection with the interplanetary magnetic field (IMF) occurs in many localized regions. This may occur not only in cusp-like structures above nearly vertical field anomalies but also in halos extending several hundreds of kilometers from these sources. Re-connection will permit solar wind (SW) and more energetic particles to precipitate into and heat the neutral atmosphere. Electron density profiles of the ionosphere of Mars derived from radio occultation data obtained by the Radio Science Mars Global Surveyor (MGS) experiment are concentrated in the near polar regions. The effective scale-height of the neutral atmosphere density in the vicinity of the ionization peak has been derived for each of the profiles studied. The effective scale-heights have been compared with the crustal magnetic fields measured by the MGS Magnetometer/Electron Reflectometer (MAG/ER) experiment. A significant difference between the large-scale mini-magnetospheres and regions outside of them has been found. The neutral atmosphere is cooler inside the large-scale mini-magnetospheres. It appears that outside of the cusps the strong crustal magnetic fields prevent additional heating of the neutral atmosphere by direct interaction of the SW. The scale-height of the neutral atmosphere density derived from the experiment with the MGS Accelerometer has been compared with MAG/ER data. The scale-height was found to be usually larger than mean value near the boundaries of potential mini-magnetospheres and around cusps . It may indicate that the paleo-magnetic/IMF field re-connection is characteristic of the mini-magnetospheres at Mars.

N F Ness↗
NASA NTRS1972

The influence of magnetic total intensity and inclination on directions preferred by migrating European robins (Erithacus rubecula)

The directional orientation of migratory European robins in relation to magnetic cues is analyzed. Major efforts were made to determine what information the birds derive from the fields. It was determined that magnetic fields provide: (1) field intensity which determines whether the magnetic field can be used for orientation, (2) a means by which axial direction may be perceived, and (3) a means by which the bird can find the north direction. The north direction is sensed from the angle between gravity and the magnetic field.

Wiltschko, W.↗
NASA NTRS1985

MHD analysis of the evolution of solar magnetic fields and currents in an active region

A self-consistent, newly developed, nonplanar MHD model is used to investigate the evolution of field and current structures in solar active regions due to photospheric shearing motions. It is demonstrated that this model can predict physical parameters that may help improve understanding of the evolution of those field and current structures. Numerical results on the magnetic energy intensity, electric current intensity, and magnetic field configuration are presented.

Wu, S. T.↗
NASA NTRS1981

The generation mechanism for magnetosheath lion roars

The origin of lion roars, intense electromagnetic whistler-mode waves which occur throughout the magnetosheath, is investigated based on particle and field data obtained on the ISEE satellites. Analysis of the measured magnetic fields, plasma densities and plasma wave intensities during periods of lion roar emission reveals the lion roar bursts to be correlated with decreases in magnetic field intensity, while the plasma density exhibits a strong anticorrelation with the magnetic field variability during the bursts and the total plasma pressure remains essentially constant. Results indicate that the waves can originate by the cyclotron resonant instability with anisotropic magnetosheath electrons whenever the magnetic energy per particle falls to values comparable with the electron thermal energy. Variations in the magnetic energy appear to be associated with the hydromagnetic mirror instability which in turn is excited by a pressure anisotropy in the magnetosheath ion population.

Thorne, R. M.↗
NASA NTRS1991

Prompt arrival of solar energetic particles from far eastern events - The role of large-scale interplanetary magnetic field structure

Intensity-time profiles of solar energetic particle enhancements generally show an asymmetry with respect to the heliolongitude of the associated solar event. Particles arrive promptly from events to the west of an observer because of good magnetic connection, whereas particle enhancements from poorly connected eastern source regions usually show much slower onsets. However, some 15 percent of eastern events do show prompt onsets. Two prompt particle enhancements associated with eastern solar events are studied using data from the Goddard Space Flight Center instruments on the ISEE 3 and IMP 8 spacecraft. In both events the prompt particle onset was observed when the spacecraft were in a postshock plasma region, apparently within a magnetic bottle. It is suggested that the magnetic bottle extended back to the sun and served as a channel for fast particle propagation to the spacecraft. Particles accelerated at an expanding coronal shock initiated by the eastern event could be injected onto field lines in the foot of the bottle.

Richardson, I. G.↗
NASA NTRS1991

Circular polarization in 1612 MHz OH maser emission from OH/IR stars

In order to study the incidence of circular polarization in the 1612 MHz OH emission from envelopes of OH/IR stars, the Arecibo radio telescope was used to obtain high-resolution, high signal-to-noise 1612 MHz spectra in both circular polarizations for several OH/IR stars. The method of Troland and Heiles (1982) was used to estimate the intensities of magnetic fields in the envelopes. The fields appear to have complex structures, and intensities on the order of 1-100 microG. The spectra are weakly polarized, probably as a result of weakly polarized emission from individual emitting elements. Integration over the Stokes parameter V yields nonzero results for three of the stars, suggesting that another polarizing mechanism (in addition to simple Zeeman splittings) is at work.

Zell, Philip↗
NASA NTRS1992

On the differences between plage and quiet sun in the solar photosphere

Time sequences of interleaved observations of the continuum intensity, longitudinal magnetic field, vertical velocity in the midphotosphere, and the line-center intensity in Ni I 6768 A were obtained in an active-region plage and the surrounding relatively field-free area near disk center. Spacetime Fourier filtering techniques are used to separate the convective and oscillatory components of the solar atmosphere. The properties of the photosphere are found to differ qualitatively and quantitatively between the plage, where the field is 150 G or more, and its quiet surroundings. The scale of granulation is smaller, the contrast lower, and the temporal evolution slower in the plage than the quiet sun. In the plage, the vertical velocity is reduced in amplitude compared to the quiet sun, and there is little evidence of a granulation pattern, while in the quiet sun the vertical flow pattern is similar in size and shape to the underlying granulation pattern in the continuum.

Title, Alan M.↗
NASA NTRS1977

The spiral configuration of sunspot magnetic fields

Distributions of circularly and linearly polarized intensities are computed using an analytical magnetic field model for an isolated sunspot, and these intensity distributions are compared with observed intensities in all Stokes parameters in the 5250-A line measured with the Marshall Space Flight Center's vector magnetograph. The qualitative agreement between measured and calculated linearly polarized intensity distributions is discussed with regard to implications as to the configuration of the transverse magnetic field of the isolated sunspot.

Hagyard, M. J.↗