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Results for “magnetization distributions”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Magnetic moment distribution of magnetic cataclysmic variables

A simulation study is made of the relative numbers of the AM Herculis binaries and the intermediate polars as a function of the orbital period using random variables subject to suitable constraints to describe the various parameters. It is shown that the observations can be matched by a single distribution in the magnetic moment equals 0.7 +/- 0.3. For such an ensemble, the intermediate polars are distributed in the log(Porb) - log(Ps) diagram about the critical disk line but with a larger scatter than observed.

Wu, Kinwah↗
NASA NTRS2003

Distributed magnetic field positioning system using code division multiple access

An apparatus and methods for a magnetic field positioning system use a fundamentally different, and advantageous, signal structure and multiple access method, known as Code Division Multiple Access (CDMA). This signal architecture, when combined with processing methods, leads to advantages over the existing technologies, especially when applied to a system with a large number of magnetic field generators (beacons). Beacons at known positions generate coded magnetic fields, and a magnetic sensor measures a sum field and decomposes it into component fields to determine the sensor position and orientation. The apparatus and methods can have a large `building-sized` coverage area. The system allows for numerous beacons to be distributed throughout an area at a number of different locations. A method to estimate position and attitude, with no prior knowledge, uses dipole fields produced by these beacons in different locations.

Prigge, Eric A.↗
NASA NTRS1986

Electrostatic instabilities of velocity-space-shell distributions in magnetized plasmas

Electron instabilities of magnetized spherical shell distributions in velocity space with a colder Maxwellian background are investigated analytically with simulations using electrostatic particle codes. The resonant and nonresonant instabilities observed in the particle simulations are in agreement with zeros of the dielectric function, as found from the resonant approximations for waves with an electric field component along the magnetic field or by computation with a root solver code in the case of perpendicular propagation. Saturation of the instabilities is by nonlinear cyclotron resonance with the cold background in the resonant case or by nonstochastic cyclotron harmonic damping by the cold background in the nonresonant case. Instabilities invariably lead to perpendicular acceleration and heating of the cold background to velocities sometimes exceeding the shell velocity.

Sentman, D. D.↗
NASA NTRS1995

The Latitudinal Distribution of Magnetic Holes in the Solar Wind

%T The Latitudinal Distribution of Magnetic Holes in the Solar Wind%A D. Winterhalter%A M. Neugebauer%A E. J. Smith%A A. Balogh%J American Geophysical Union, 1995 Spring Meeting%C Baltimore, Maryland%D May 29-June 2, 1995%K Interplanetary Magnetic Fields%K Solar Wind%U http://techreports.jpl.nasa.gov/1995/95-0554.pdf!

Interplanetary↗
NASA NTRS1995

On the spatial distribution of magnetic fields on the solar surface

Recent measurements of solar surface magnetic fields suggest that the spatial distribution of these fields is fractal. In order to understand the physical basis for such geometric complexity, we study here the advection of magnetic flux tubes relatively simple random motions on the surface of a fluid and investigate the spatial statistics of the resulting surface field. While this study does not directly address the question of why solar surface fields have the observed spatial structure, it is designed to build our intuition about how surface flows lead to complex spatial structuring of magnetic fields. As part of our study, we discuss the various methods by which one can describe the spatial distribution of the surface magnetic flux and relate them mathematically; this turns out to be a crucial point of our work since, as we show, a number of previous analyses have misinterpreted the analysis procedures for determining fractal dimensions. Our principal result is the explicit demonstration that simple random flows lead to magnetic flux spatial distributions with a multifractal dimension spectrum. Furthermore, we demonstrate that this magnetic spatial structure is generic, i.e., is characteristic of a very large class of random flows.

Tao, L.↗
NASA NTRS1990

Magnetic field distribution in polar cap models of gamma-ray bursters

The high-energy spectral cutoffs are discussed as a function of angle predicted by magnetized polar cap models of gamma-ray bursters, in the presence of magnetic pair production and general relativistic effects. The effect of the photon escape beam shape on the relative probability of detection as a function of energy is calculated for a range of model parameters. These predictions are compared to the burster cutoff upper limits observed with SMM and are used to derive constraints on the detectable magnetic field strength distribution among bursters from future observations. A method for determining the intrinsic magnetic field distribution among gamma-ray bursting neutron stars is discussed.

Bagoly, Z.↗
NASA NTRS1995

Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa2Cu3O7 thin films

Mapping of the magnetic flux density B(sub z) (perpendicular to the film plane) for a YBa2Cu3O7 thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B(sub z) distributions. From the known sheet magnetization, the tangential (B(sub x,y)) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B(sub x,y)/d, where d is the film thickness. The evolution of flux penetration as a function of applied field will be shown.

Xing, W.↗
NASA NTRS1987

The period and magnetic field distributions of cataclysmic variables - Implications for their evolution

Comparison of the period distributions of various classes of CVs confirms an extreme bias of the synchronous AM Her systems toward short orbital periods, while the DQ Her systems do not differ significantly from the distribution of nonmagnetic systems. This suggests either strong selection effects or enhanced evolution of the AM Her systems. There is as yet no obvious bimodality in either the magnetic field distributions of isolated white dwarfs or of CV primaries. However, clear differences between the two exist: the strongest being that magnetic primaries are overrepresented among short period CVs by more than an order of magnitude in comparison to the field white dwarfs.

Schmidt, G. D.↗
NASA NTRS2003

CMEs, the Tail of the Solar Wind Magnetic Field Distribution, and 11-yr Cosmic Ray Modulation at 1 AU

Using a recent classification of the solar wind at 1 AU into its principal components (slow solar wind, high-speed streams, and coronal mass ejections (CMEs) for 1972-2000, we show that the monthly-averaged galactic cosmic ray intensity is anti-correlated with the percentage of time that the Earth is imbedded in CME flows. We suggest that this correlation results primarily from a CME related change in the tail of the distribution function of hourly-averaged values of the solar wind magnetic field (B) between solar minimum and solar maximum. The number of high-B (square proper subset 10 nT) values increases by a factor of approx. 3 from minimum to maximum (from 5% of all hours to 17%), with about two-thirds of this increase due to CMEs. On an hour-to-hour basis, average changes of cosmic ray intensity at Earth become negative for solar wind magnetic field values square proper subset 10 nT.

Cliver, E. W.↗
NASA NTRS1988

The longitudinal and radial distribution of magnetic reconfigurations in the near-earth magnetotail as observed by AMPTE/CCE

The longitudinal and radial distribution of 103 substorm dipolarization events in the equatorial nightside magnetosphere from low altitude to about 9 R(E) observed by AMPTE/CCE is examined. The center of the distribution was located near midnight. For Kp of 3- or less, the distribution peak shifted toward the premidnight region, whereas for Kp of 4+ and higher, the distribution peak was inside the postmidnight region. The substorm frequency for the high-Kp case was about four times larger than the low-to-moderate-Kp case. The occurrence frequency of events increased with increasing radial distance, and no events were observed inside of 6.4 R(E). This radial distribution suggests that, on average, the substorm initiation region is greater than about 8 R(E). In addition, the average radial position of the signatures decreased with increasing Kp.

Lopez, R. E.↗
NASA NTRS1994

Shape, size, and distribution of magnetic particles in Bjurbole chondrules

Chondrules from the Bjurbole chondritic meteorite (L4) exhibit saturation remanence magnetization (SIRM) values which vary over three orders of magnitude. REM values (Natural Remanence Magnetization/SIRM) for Allende (C3V) and Chainpur (LL3) are less than 0.01 but in Bjurbole some chondrules were found to have REM values greater than 0.1 with several greater than 0.2. REM values greater than 0.1 are abnormal and cannot be acquired during weak field cooling. If exposure to a strong field (whatever the source) during the chondrules' history is responsible for the high REM values, was such history associated with a different processing which might have resulted in different shape, size, and distribution of metal particles compared to chondrules having REM values of less than 0.01? Furthermore, magnetic hysteresis results show a broad range of magnetic hardness and other intrinsic magnetic properties. These features must be related to (1) size and amount of metal; and (2) properties of, and amount of, tetrataenite in the chondrules (all chondrules thus far subjected to thermomagnetic analysis show the presence of tetrataenite). A scanning electron microscopy (SEM) study is underway to determine the relationship between the shape, size, and distribution of metal particles within individual chondrules and the magnetic properties of these chondrules. Results from the SEM study in conjunction with magnetic property data may also help to discern effects from possible lightning strikes in the nebula prior to incorporation of the chondrules into the parent body.

Nava, David F.↗
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.↗