Theory of the solar magnetic cycle wave in the diurnal variation of energetic cosmic rays - Physical basis of the anisotropy
Explore the source record for details and available documents.
Levy, E. H.↗
SEARCH · Search NASA
Results for “anisotropy”
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.
Fluxes of protons above 50 keV and electrons above 30 keV at approximately 35 earth radii. I - Velocity anisotropies and plasma flow in the magnetotail. II Morphology and flow patterns in the magnetotail
Imp-7 data were used to study the morphology and flow patterns of energetic proton and electron events in the magnetotail and magnetosheath at 35 earth radii. The patterns are deduced from the probability of occurrence and the spatial distribution of the events. The distribution of 50 to 200 keV proton and 30 to 90 keV electron fluxes shows that in the magnetotail (i.e., inside the magnetopause) the proton and electron events occur primarily in the plasma sheet region within plus or minus 10 earth radii of the neutral sheet; fluxes of 50- to 200-keV protons are also found in the magnetosheath, along with occasional fluxes of 30- to 90-keV electrons; the plasma sheet is well defined (at 35 earth radii) by both the proton and electron probabilities; the frequency of the electron events in the magnetotail shows a positive correlation with the geomagnetic Kp index in the dawn and dusk sectors.
Roelof, E. C.↗
Studies on solar hard X-Rays and gamma-rays: Compton backscatter, anisotropy, polarization and evidence for two phases of acceleration
Observations of solar X-rays and gamma-rays from large flares show that the hard X-ray spectrum extends into the gamma ray region, where a flattening in the spectrum of the continuum emission is observed above about 1 MeV. This emission is believed to be due to bremsstrahlung. In addition to electron-proton collisions, at energies greater than approximately 500 keV, bremsstrahlung due to electron-electron collisions becomes significant. Bremsstrahlung production was calculated for a variety of electron spectra extending from the nonrelativistic region to relativistic energies and electron-electron bremsstrahlung is taken into account. By comparing these calculations with data, it is shown that the flattening in the spectrum of the continuum emission can be best explained by an electron spectrum consisting of two distinctive components. This evidence, together with information on the X-ray and gamma ray time profiles, implied the existence of two phases of acceleration. The first phase accelerates electrons mainly up to about several hundred keV; the second phase accelerates a small fraction of the electrons accelerated in the first phase to relativistic energies and accelerates protons to tens and hundreds of MeV.
Bai, T.↗
Observation of a north-south anisotropy of atmospheric radiation at balloon altitudes
Measurements have been made of an azimuthal asymmetry of atmospheric radiation at balloon altitudes and mid-latitudes. The measured asymmetry is 6% peak to peak in the north-south direction at energies above 500 keV. A lack of east-west asymmetry indicates that the arrival direction of the atmospheric radiation is highly decoupled from that of the primary radiation. Present models of secondary atmospheric radiation production and transport do not quantitatively agree with the observations.
Fishman, G. J.↗
A mechanism for pressure anisotropy and mirror instability in the dayside magnetosheath
Explore the source record for details and available documents.
Crooker, N. U.↗
Possible evidence for large, transient electric fields in the magnetotail from oppositely directed anisotropies of energetic protons and electrons
Explore the source record for details and available documents.
Kirsch, E.↗
Theory of flux anisotropies in a guiding center plasma
The one particle distribution function f on the scale of the bounce motion of particles in a magnetic field B is considered. The Vlasov equation is expanded through O(epsilon) in the adiabatic parameter which is the ratio of particle gyroradius to scale length of the magnetic field. Because f is directly proportional to particle flux differential in kinetic energy and solid angle, f is in principle measurable in space experiments, and the analysis is tailored to be explicitly applicable to space problems. To O(1), f is gyrotropic; its first velocity moment is (if non-vanishing) parallel to B, and hence macroscopic parallel flow is included in this term. The O(epsilon) contribution is non-gyrotropic and macroscopic flow parallel to B plus additional parallel flow results from these terms. The degree of non-gyrotropy and the amount of cross-field macroscopic flow depend on the perpendicular component of the electric field, on curvature and shear in the magnetic field, and on the spatial gradient, pitch angle derivative, and speed derivative of the lowest order distribution function.
Birmingham, T. J.↗
Interpretation and analysis of solar energetic particle intensities and anisotropies observed aboard Helios 2 on 28 March 1976
Explore the source record for details and available documents.
Bieber, J. W.↗
The effect of dilatancy on velocity anisotropy in Westerly granite
Jacketed samples of Westerly granite were fractured at confining pressures up to 1 kbar, and compressional and horizontally as well as vertically polarized shear velocities were measured in orthogonal directions perpendicular to the compression axis. Changes occurring with increased strain are described, and the velocity data were analyzed by application of the Anderson et al (1974) approach. Observed and calculated velocities are found to be in good agreement, and the degree of dilatancy was determined from the differences between the strains measured perpendicularly to the compression axis and the estimated elastic strains in those directions.
Soga, N.↗
The effect of surface anisotropy on the accuracy of total ozone estimates from satellite observations
The total amount of ozone in a vertical column of the earth's atmosphere is being derived from satellite measurements of the intensity of ultraviolet sunlight scattered by the earth-atmosphere system. The algorithm for deriving the ozone amount utilizes the assumption that the earth's surface reflects the incident light isotropically according to Lambert's law. Natural surface reflection deviates more or less from this law. Two extreme examples of anisotropic reflection from dark ocean and from bright snow are analyzed by means of models for their effects on the derived values of ozone.
Fraser, R. S.↗
Theory of flux anisotropies in a guiding center plasma
Assuming time stationarity of the one-particle distribution function f on the scale of the bounce motion of particles in a magnetic field, the paper expands the Vlasov equation through O(epsilon) in the adiabatic parameter epsilon, which is the ratio of particle gyroradius to scale length of the magnetic field. Since f is directly proportional to particle flux differential in kinetic energy and solid angle, f is in principle measurable in space experiments, and the present analysis is tailored to be explicitly applicable to space problems. It is shown that the usual expression for the electric field which produces plasma corotation in an axisymmetric system such as a dipole also holds for any nonaxisymmetric but rigidly rotating magnetic field pattern, provided the observed magnetic field is used in place of the dipole field. The analysis is applied to the electric field in a rigidly corotating magnetosphere.
Birmingham, T. J.↗
Anisotropy of nickel-base superalloy single crystals
The influence of orientation on the tensile and stress rupture behavior of 52 Mar-M247 single crystals was studied. Tensile tests were performed at temperatures between 23 and 1093 C; stress rupture behavior was examined between 760 and 1038 C. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factor contours for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The tensile properties correlated well with the appropriate Schmid factor contours. The stress rupture lives at lower testing temperatures were greatly influenced by the lattice rotations required to produce cross slip. A unified analysis was attained for the stress rupture life data generated for the Mar-M247 single crystals at 760 and 774 C under a stress of 724 MPa and the data reported for Mar-M200 single crystals tested at 760 C under a stress of 689 MPa. Based on this analysis, the stereographic triangle was divided into several regions which were rank ordered according to stress rupture life for this temperature regime.
Mackay, R. A.↗
Anisotropy of nickel-base superalloy single crystals
The effects of crystal orientation on the mechanical properties of single crystals of the nickel-based superalloy Mar-M247 are investigated. Tensile tests at temperatures from 23 to 1093 C and stress rupture tests at temperatures from 760 to 1038 C were performed for 52 single crystals at various orientations. During tensile testing between 23 and 760 C, single crystals with high Schmid factors were found to be favorably oriented for slip and to exhibit lower strength and higher ductility than those with low Schmid factors. Crystals which required large rotations to become oriented for cross slip were observed to have the shortest stress rupture lives at 760 C, while those which required little or no rotation had the longest lives. In addition, stereographic triangles obtained for Mar-M247 and Mar-M200 single crystals reveal that crystals with orientations near the -111 had the highest lives, those near the 001 had high lives, and those near the 011 had low lives.
Mackay, R. A.↗
The effect of the charge exchange source on the velocity and 'temperature' distributions and their anisotropies in the earth's exosphere
The velocity distribution of atomic hydrogen in the earth's exosphere is calculated as a function of altitude and direction taking into account both the classic exobase source and the higher-altitude plasmaspheric charge exchange source. Calculations are performed on the basis of a Monte Carlo technique in which random ballistic trajectories of individual atoms are traced through a three-dimensional grid of audit zones, at which relative concentrations and momentum or energy fluxes are obtained. In the case of the classical exobase source alone, the slope of the velocity distribution is constant only for the upward radial velocity component and increases dramatically with altitude for the incoming radial and transverse velocity components, resulting in a temperature decrease. The charge exchange source, which produces the satellite hydrogen component and the hot ballistic and escape components of the exosphere, is found to enhance the wings of the velocity distributions, however this effect is not sufficient to overcome the temperature decreases at altitudes above one earth radius. The resulting global model of the hydrogen exosphere may be used as a realistic basis for radiative transfer calculations.
Hodges, R. R., Jr.↗
Uppermantle anisotropy and the oceanic lithosphere
Published Rayleigh and Love wave phase and group velocity data have been inverted taking into account sphericity, anelastic dispersion, and transverse isotropy. For a PREM-type modular parameterization, the thickness of the high velocity mantle seismic lithosphere (LID) varies in thickness from about 30 km for young ocean to about 50 km for old ocean, much less than previous estimates based on isotropic inversion of similar data. This LID thickness is comparable to the elastic or flexural thickness found from studies of seamount loading and flexure at trenches, suggesting that the thickness of the lithosphere may be controlled by mineralogy, composition, or crystal orientation rather than by temperature alone.
Anderson, D. L.↗
Sound velocity anisotropy in cubic crystals
Simple analytical expressions may be derived for sound velocities in cubic crystals by using lattice harmonics or functions which are invariant under the crystal symmetry operations. These expressions are in good agreement with the exact results for typical crystals such as metallic iron and potassium fluoride.
Tsang, T.↗
Demonstration of angular anisotropy in the output of Thematic Mapper
There is a dependence of TM output (proportional to scene radiance in a manner which will be discussed) upon season, upon cover type and upon view angle. The existence of a significant systematic variation across uniform scenes in p-type (radiometrically and geometrically pre-processed) data is demonstrated. Present pre-processing does remove the effects and the problem must be addressed because the effects are large. While this is in no way attributable to any shortcomings in the thematic mapper, it is an effect which is sufficiently important to warrant more study, with a view to developing suitable pre-processing correction algorithms.
Duggin, M. J.↗
Measurements of mantle wave velocities and inversion for lateral heterogeneity and anisotropy. I - Analysis of great circle phase velocities
The global lateral heterogeneity of the upper mantle is investigated using the classical Fourier-transform method of Sato(1958) and IDA/GDSN data from 25 1980 earthquakes. The great-circle phase velocities of 200 Love and 250 Rayleigh 100-330-sec-period fundamental-mode wave paths are determined and interpreted in terms of regional phase-velocity variation, using additional data on surface tectonics to extrapolate odd-harmonic information from the even-harmonic data. The results are presented in extensive tables, maps, and graphs. Regionalized inversion using the seven-region model of Okal (1977) is found to give maximum variance reductions of 65 percent for Love waves and 85 percent for Rayleigh waves, compared to 60 and 90 percent for l(max) = 2 inversion. Significant interregion differences are found in the regionalized Love-wave phase velocities.
Nakanishi, I.↗