Search NASA⌕ Search

SEARCH · Search NASA

Results for “MAGNETIC COMPRESSION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Processing SAR Images On Board

Synthetic-aperture radar (SAR) processor operates aboard moving radar platform, turning raw signal data into images of scanned terrain. In conventional SAR systems, raw data either transmitted to stations on ground or recorded on magnetic tape by high-density digital recorders for subsequent processing on ground. Advantages include making SAR images available immediately and processed data transmitted or recorded only one-fifth as voluminous as raw data. Onboard image compression reduces volume of data even further.

Liu, Kuang Y.↗
NASA NTRS1994

On the energy principle and ion tearing in the magnetotail

We re-examine the use of the energy principle as applied to the tearing instability in the magnetotail. We demonstrate that when a magnetic field component normal to the current sheet is present, electron pitch-angle diffusion (PAD) either by micro-turbulence or by chaotic orbits cannot remove the strong stabilization of the tearing mode caused by electron compressibility. We find that our conclusions are in agreement with those of Pellat et al. (1991), who argued on the basis of canonical P(sub y) conservation that the stabilization of the ion tearing mode cannot be removed by the introduction of PAD. Our results are at variance with those of Kuznetsova and Zelenyi (1991), who argued that the application of the energy principle used by Pellat et al. (1991) is incorrect, and that tearing is in fact unstable in the limit of strong PAD. We show that the disagreement between these two studies can be traced to an incorrect orbit evaluation first introduced by Coroniti (1980) and subnsequently used by Kuznetsova and Zelenyi (1991).

Brittnacher, M.↗
NASA NTRS1995

Penetration of the Interplanetary Magnetic Field B(sub y) into Earth's Plasma Sheet

There has been considerable recent interest in the relationship between the cross-tail magnetic field component B(sub y) and tail dynamics. The purpose of this paper is to give an overall description of the penetration of the interplanetary magnetic field (IMF) B(sub y) into the near-Earth plasma sheet. We show that plasma sheet B(sub y) may be generated by the differential shear motion of field lines and enhanced by flux tube compression. The latter mechanism leads to a B(sub y) analogue of the pressure-balance inconsistency as flux tubes move from the far tail toward the Earth. The growth of B(sub y), however, may be limited by the dawn-dusk asymmetry in the shear velocity as a result of plasma sheet tilting. B(sub y) penetration into the plasma sheet implies field-aligned currents flowing between hemispheres. These currents together with the IMF B(sub y) related mantle field-aligned currents effectively shield the lobe from the IMF B(sub y).

Hau, L.-N.↗
NASA NTRS2003

Divergence Free High Order Filter Methods for Multiscale Non-ideal MHD Flows

Low-dissipative high order filter finite difference methods for long time wave propagation of shock/turbulence/combustion compressible viscous MHD flows has been constructed. Several variants of the filter approach that cater to different flow types are proposed. These filters provide a natural and efficient way for the minimization of the divergence of the magnetic field (Delta . B) numerical error in the sense that no standard divergence cleaning is required. For certain 2-D MHD test problems, divergence free preservation of the magnetic fields of these filter schemes has been achieved.

Yee, H. C.↗
NASA NTRS2003

High Order Filter Methods for Shock/Turbulence MHD Flows

Low-dissipative high order filter finite difference methods for shock/turbulence/combustion compressible viscous MHD flows has been constructed. Several variants of the filter approach that cater to different flow types are proposed. These filters provide a natural and efficient way for the minimization of the divergence of the magnetic field (del (raided dot) B) numerical error in the sense that no standard divergence cleaning is required. For certain 2-D MHD test problems, divergence free preservation of the magnetic fields of these filter schemes has been achieved.

Yee, H. C.↗
NASA NTRS2004

Adaptive Low Dissipative High Order Filter Methods for Multiscale MHD Flows

Adaptive low-dissipative high order filter finite difference methods for long time wave propagation of shock/turbulence/combustion compressible viscous MHD flows has been constructed. Several variants of the filter approach that cater to different flow types are proposed. These filters provide a natural and efficient way for the minimization of the divergence of the magnetic field [divergence of B] numerical error in the sense that no standard divergence cleaning is required. For certain 2-D MHD test problems, divergence free preservation of the magnetic fields of these filter schemes has been achieved.

Yee, H. C.↗
NASA NTRS1992

Interaction of fast steady flow with slow transient flow - A new cause of shock pair and interplanetary B(z) event

The occurrence of the nonspiral magnetic field (high helium density) Cold Magnetic Enhancement and counterstreaming suprathermal electron flux in the slow flow around the forward shock indicates that the slow flow is a CME in interplanetary space (ICME). The characteristics of the field and plasma in the fast flow around the reverse shock is typical for a high speed stream. Thus the shock pair here appears to be caused by the interaction of a high speed stream with a slow ICME. The fact that a -B(z) event occurred in such a shock pair suggests that the slow ICME is disconnected from the sun. It is shown that compression alone appears to be adequate to explain the large southward IMF component within the shocked plasma because of the large southward field component present in the ICME ahead of the forward shock. In addition, a new method to infer the shock angle and Mach number from the observed upstream plasma B and the jump ratios of proton density and total magnetic flux density across a shock is described.

Zhao, Xuepu↗
NASA NTRS1971

Unique intermetallic compounds prepared by shock wave synthesis

Technique compresses fine ground metallic powder mixture beyond crystal fusion point. Absence of vapor pressure voids and elimination of incongruous effects permit application of technique to large scale fabrication of intermetallic compounds with specific characteristics, e.g., semiconduction, superconduction, or magnetic properties.

Otto, G.↗
NASA NTRS1981

Statistical properties of MHD fluctuations associated with high speed streams from HELIOS 2 observations

Helios 2 magnetic data were used to obtain several statistical properties of MHD fluctuations associated with the trailing edge of a given stream served in different solar rotations. Eigenvalues and eigenvectors of the variance matrix, total power and degree of compressibility of the fluctuations were derived and discussed both as a function of distance from the Sun and as a function of the frequency range included in the sample. The results obtained add new information to the picture of MHD turbulence in the solar wind. In particular, a dependence from frequency range of the radial gradients of various statistical quantities is obtained.

Bavassano, B.↗
NASA NTRS1993

The Third NASA Goddard Conference on Mass Storage Systems and Technologies

This report contains copies of nearly all of the technical papers and viewgraphs presented at the Goddard Conference on Mass Storage Systems and Technologies held in October 1993. The conference served as an informational exchange forum for topics primarily relating to the ingestion and management of massive amounts of data and the attendant problems involved. Discussion topics include the necessary use of computers in the solution of today's infinitely complex problems, the need for greatly increased storage densities in both optical and magnetic recording media, currently popular storage media and magnetic media storage risk factors, data archiving standards including a talk on the current status of the IEEE Storage Systems Reference Model (RM). Additional topics addressed System performance, data storage system concepts, communications technologies, data distribution systems, data compression, and error detection and correction.

Kobler, Benjamin↗
NASA NTRS2017

Gradient Field Imploding Liner Fusion Propulsion System

Magneto-inertial fusion concepts often use a pulsed high current discharge in a cylindrical coil to generate a rapidly changing axial magnetic field, inducing a counter-propagating current in the conducting outer liner of a centrally aligned cylindrical fusion target. The Lorentz force arising from the axial field and azimuthal liner current rapidly implodes the target radially inward, compressing the fuel to reach fusion conditions.

Exploration↗
NASA NTRS2018

Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere

We present Van Allen Probe observations of electromagnetic ion cyclotron (EMIC) waves triggered solely due to individual substorm-injected ions in the absence of storms or compressions of the magnetosphere during 9 August 2015. The time at which the injected ions are observed directly corresponds to the onset of EMIC waves at the location of Van Allen Probe A (L = 5.5 and 18:06 magnetic local time). The injection was also seen at geosynchronous orbit by the Geostationary Operational Environmental Satellite and Los Alamos National Laboratory spacecraft, and the westward(eastward) drift of ions(electrons) was monitored by Los Alamos National Laboratory spacecraft at different local times. The azimuthal location of the injection was determined by tracing the injection signatures backward intime to their origin assuming a dipolar magnetic field of Earth. The center of this injection location wasdetermined to be close to 20:00 magnetic local time. Geostationary Operational Environmental Satelliteand ground magnetometer responses confirm substorm onset at approximately the same local time.The observed EMIC wave onsets at Van Allen Probe were also associated with a magnetic field decrease.The arrival of anisotropic ions along with the decrease in the magnetic field favors the growth of the EMICwave instability based on linear theory analysis.

Van Allen Probes↗
NASA NTRS1973

Solar wind interaction with lunar magnetic fields.

Two basic interaction modes have been identified: (1) deflection currents that close above the surface, typified by a subsurface dipole with its axis perpendicular to the surface, and (2) deflection currents that intersect the lunar surface, typified by a subsurface dipole with its axis parallel to the surface. The first results in a compression of the lunar field and, if it is strong enough, can stop the wind above the surface. The extent of compression depends on how much the wind is slowed before striking the surface. The second mode results in a small deflection of the wind. In both modes, charging up of the surface is important. The effects of discharging the surface charge through the photolayer and the lunar crust are found to be unimportant for typical lunar parameters.

Siscoe, G. L.↗
NASA NTRS2005

Magnetically Attached Multifunction Maintenance Rover

A versatile mobile telerobot, denoted the magnetically attached multifunction maintenance rover (MAGMER), has been proposed for use in the inspection and maintenance of the surfaces of ships, tanks containing petrochemicals, and other large ferromagnetic structures. As its name suggests, this robot would utilize magnetic attraction to adhere to a structure. As it moved along the surface of the structure, the MAGMER would perform tasks that could include close-up visual inspection by use of video cameras, various sensors, and/or removal of paint by water-jet blasting, laser heating, or induction heating. The water-jet nozzles would be mounted coaxially within compressed-air-powered venturi nozzles that would collect the paint debris dislodged by the jets. The MAGMER would be deployed, powered, and controlled from a truck, to which it would be connected by hoses for water, compressed air, and collection of debris and by cables for electric power and communication (see Figure 1). The operation of the MAGMER on a typical large structure would necessitate the use of long cables and hoses, which can be heavy. To reduce the load of the hoses and cables on the MAGMER and thereby ensure its ability to adhere to vertical and overhanging surfaces, the hoses and cables would be paid out through telescopic booms that would be parts of a MAGMER support system. The MAGMER would move by use of four motorized, steerable wheels, each of which would be mounted in an assembly that would include permanent magnets and four pole pieces (see Figure 2). The wheels would protrude from between the pole pieces by only about 3 mm, so that the gap between the pole pieces and the ferromagnetic surface would be just large enough to permit motion along the surface but not so large as to reduce the magnetic attraction excessively. In addition to the wheel assemblies, the MAGMER would include magnetic adherence enhancement fixtures, which would comprise arrays of permanent magnets and pole pieces that could be adjusted to maximize or minimize the overall attractive magnetic force. Even with a paint thickness of 2 mm, a preliminary design provides a safety factor of 5 in the magnetic force in the upside- down, water-jets-operating condition, in which the total load (including the weight of the MAGMER and cables and the water-jet force) would be about 260 lb (the weight of 118 kg). Optionally, the MAGMER could carry magnetic shielding and/or could be equipped with a demagnetizing module to remove residual magnetism from the structure. The MAGMER would carry four charge-coupled-device cameras for visual inspection, monitoring of operation, navigation, and avoidance of collisions with obstacles. The control system of the MAGMER would include navigation and collision-avoidance subsystems that would utilize surface features as landmarks, in addition to direct images of obstacles.

Bar-Cohen, Yoseph↗
NASA NTRS1973

Effects of interhemisphere transport on plasma temperatures at low latitudes.

The thermal balance of the equatorial plasma between 300 and 800 km is examined. Steady state nighttime calculations are made for O+, H+, and electrons. The following features are included: collisional heat transfer between ions, electrons, and neutrals; ion and electron thermal conduction along the field lines; curvature of the field lines; nonlinear advection due to field-aligned ion and electron motions; and convective compression or expansion due to field-aligned and E x B motions. The ion velocities necessary to calculate the effects of convection are obtained from the work of Moffett and Hanson, who include a meridional wind across the magnetic equator in their calculations. It is shown that field-aligned interhemisphere plasma flows appreciably affect the plasma temperatures.

Bailey, G. J.↗
NASA NTRS1994

The proton cyclotron instability and the anisotropy/B inverse correlation

Spacecraft observations in the strongly compressed subsolar magnetosheath show an inverse correlation between the proton temperature anistrophy (T(sub perpendicular to p)/T(sub parallel to p) greater than 1 where perpendicular to and parallel to denote directions perpendicular and parallel to the background magnetic field) and the parallel proton beta (beta(sub parallel to p). This manuscript uses one-dimensional hybrid simulations of the proton cyclotron anisotropy instability in homogeneous electron-proton plasmas to study this correlation which may represent a limited closure relation for fluid theories of anisotropic space plasmas. The emphasis is on driven simulation which increase the temperature anisotropy by periodically reducing the magnetic-field-aligned velocities of the protons. The late-time states from ensembles of both initial value and driven simulations yield very similar expressions for the proton anisotropy/beta(sub parallel to P) inverse correlation, and provide a basis for explaining differences between sheath observations from different spacecraft. The driven simulations also yield expressions for the maximum instability growth rate and the fluctuating field energy as functions of beta (sub parallel to p) and a parameter characterizing the anisotropy driver.

Gary, S. Peter↗
NASA NTRS2003

Journey to the Center of a Neutron Star

A neutron star is not a place most would want to visit. This dense remnant of a collapsed star has a magnetic field billions of times stronger than Earth's, enough to shuffle your body's molecules long before you even land. The featureless surface is no fun either. Crushing gravity ensures that the star is a near perfect sphere, compressing all matter so that a sand-grain-sized scoop of neutron star material would weigh as much as a battleship on Earth. At least black holes offer the promise of funky singularity, time warps, and the Odyssean temptation to venture beyond a point of no return. What s a journey to a neutron star good for, one might ask? Well, for starters, it offers the possibility of confirming a theorized state of matter called quark-gluon plasma, which likely existed for a moment after the Big Bang and now might only exist in the superdense interiors of neutron stars. Beneath the neutron star crust, a kilometer-thick plate of crystalline matter, lies the great unknown. The popular theory is that the neutron star interior is made up of a neutron superfluid - a fluid without friction. With the help of two NASA satellites - the Rossi X-Ray Timing Explorer and the Chandra X-Ray Observatory - scientists are journeying to the center of a neutron star. Matter might be so compressed there that it breaks down into quarks, the building blocks of protons and neutrons, and gluons, the carrier of the strong nuclear force. To dig inside a neutron star, no simple drill bit will do. Scientists gain insight into the interior through events called glitches, a sudden change in the neutron star s precise spin rate. 'Glitches are one of the few ways we have to study the neutron star interior,' says Frank Marshall of NASA s Goddard Space Flight Center, who has used the Rossi Explorer to follow the escapades of the glitchiest of all neutron stars, dubbed the Big Glitcher and known scientifically as PSR J0537-6910.

Wanjek, Christopher↗
NASA NTRS1981

An acceleration mechanism for loop transients in the outer corona

The heliocentrifugal motion of coronal loop transients is likely driven largely by the buoyant force exerted by the ambient medium. In the outer corona where the solar wind is well formed, the buoyant force results mainly from the rapid outward decrease in the ambient pressure of the solar wind. The contribution from magnetic buoyancy is not so significant as in the vicinity of the solar surface. Therefore, the pertinent features of the loop transients in the outer corona are basically gasdynamical. As a conspicuous part of coronal expansion, the motion of the compressible masses in the transient loops is largely controlled by thermal forces. The translational motion of heliocentrifugal expansion is driven by the hydrodynamic buoyant force, and the lateral motion of peripheral expansion is driven by the pressure difference between the dense plasma of the ejecta and the tenuous plasma of the ambient medium.

Yen, T.↗