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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Radial and latitudinal variations of the interplanetary magnetic field

This paper presents observations of the radial and latitudinal variations of the interplanetary magnetic field measured by the Voyager 1 (V1) and Voyager 2 (V2) spacecraft from mid-1977 to mid-1985. Observations of the radial variation of the large-scale magnetic field strength in the ecliptic agree with the predictions of Parker's (1958, 1963) model when temporal variations in the magnetic field and bulk speed are taken into account. The latitudinal variation of the magnetic field observed by V1 is in agreement with the predictions of Parker's model to first approximation. The magnetic field strength at higher latitudes is somewhat lower than expected on the basis of observations made in the ecliptic, but this could be due to an increase in bulk speed and/or a decrease of solar magnetic field strength with latitude. Fluctuations in the strength of the magnetic field are small compared to the large-scale field itself, and they decrease in amplitude with increasing distance approximately as R exp -1/4 . Fluctuations in the components are relatively large, and they make a significant contribution to the mean field that is not described by Parker's model.

Klein, Larry W.↗
NASA NTRS1985

Theoretical interpretation of the observed interplanetary magnetic field radial variation in the outer solar system

Observations of the azimuthal component of the IMF are evaluated through the use of an MHD model which shows the effect of magnetic flux tubes opening in the outer solar system. It is demonstrated that the inferred meridional transport of magnetic flux is consistent with predictions by the MHD model. The computed azimuthal and radial magnetic flux deficits are almost identical to the observations. It is suggested that the simplest interpretation of the observations is that meridional flows are created by a direct body force on the plasma. This is consistent with the analytic model of Nerney and Suess (1975), in which such flux deficits in the IMF arise naturally from the meridional gradient in the spiralling field.

Suess, S. T.↗
NASA NTRS1979

Variations of the earth's magnetic field and rapid climatic cooling: A possible link through changes in global ice volume

A possible relationship between large scale changes in global ice volume, variations in the earth's magnetic field, and short term climatic cooling is investigated through a study of the geomagnetic and climatic records of the past 300,000 years. The calculations suggest that redistribution of the Earth's water mass can cause rotational instabilities which lead to geomagnetic excursions; these magnetic variations in turn may lead to short-term coolings through upper atmosphere effects. Such double coincidences of magnetic excursions and sudden coolings at times of ice volume changes have occurred at 13,500, 30,000, 110,000, and 135,000 YBP.

Rampino, M. R.↗
NASA NTRS1974

Average daily variations in the magnetic field as observed by ATS-5

Hourly averages of the magnetic field components are determined and analyzed using the measurements of the magnetic field monitor aboard the ATS-5. The data covering the time period of September 1969 through September 1971 are sorted and analyzed for various Kp values, geomagnetic latitude of the subsolar point, and local time. Local time variations are harmonically analyzed, and amplitudes and phases are given up to the fourth harmonic.

Skillman, T. L.↗
NASA NTRS1972

Average daily variations in the magnetic field as observed by ATS-5

Hourly averages of the magnetic field components are determined and analyzed using the measurements, by the magnetic field monitor (MFM) aboard the ATS-5 satellite. The data covering the time period of September 1969 through September 1971 are sorted and analyzed for various Kp values, geomagnetic latitude of the subsolar point, and local time. Local time variations are harmonically analyzed, and amplitudes and phases are given up to the fourth harmonic.

Skillman, T. L.↗
NASA NTRS2009

Radial and Solar Cycle Variations of the Magnetic Fields in the Heliosheath: Voyager 1 Observations from 2005 to 2008

We discuss the magnetic field strength B(t) and polarity observed by Voyager 1 (V1) in the heliosheath at the heliographic latitude approximately equal 34 deg as it moved away from the sun from 2005 through 2008.82. The pattern of the polarity of the magnetic field changed from alternating positive and negative polarities to predominantly negative polarities (magnetic fields pointing along the Archimedean spiral field angle toward the sun) at approximately equal 2006.23). This transition indicates that the latitudinal extent of the heliospheric current sheet (HCS) was decreasing in the supersonic solar wind, as expected for the declining phase of the solar cycle, and as predicted by extrapolation of the magnetic neutral line near the photosphere to the position of V1. However, the polarity was not uniformly negative in during 2008, in contrast to the predicted polarity. This difference suggests that the maximum latitudinal extent of the HCS was tending to increase in the northern hemisphere in the heliosheath, while it was decreasing in the supersonic solar wind. The large-scale magnetic field strength B(t) HCS was observed by V1 from 2005 through 2008.820. During this interval of decreasing solar activity toward solar minimum, B(t) at 1 AU was decreasing and the solar wind speed V at the latitude of V1 was increasing. Adjusting the temporal profile of B(t) observed by V1 for the solar cycle variations of B and V in the supersonic solar wind, we find that the radial gradient of B(R) in heliosheath from the radial distance R = 94.2 AU to 107.9 AU between 2005.0 and 2008.82 was 0.0017 nT/AU <= grad B <= 0.0055 nT/AU or grad B = (0.0036 +/- 0.0019) nT/AU

Burlaga, Leonard↗
DOE OSTI2024

Exact-Two-Component Complete Active Space Method with Variational Treatment of Magnetic Field and Spin–Orbit Coupling: Application to X-ray Magnetic Circular Dichroism Spectroscopy

We introduce an exact-two-component complete active space self-consistent-field (X2C-CASSCF) method formulated under the restricted-magnetic-balance condition. This framework allows for the nonperturbative treatment of static magnetic fields using gauge-including atomic orbitals (GIAOs). The GIAO-X2C-CASSCF methodology effectively captures all microstates within the same 2J + 1-degenerate manifold and their splitting in a static magnetic field, which are not accessible through single-reference-based methods. We also present mathematical recursive expressions for evaluating one-electron relativistic integrals by using GIAOs in the presence of a finite magnetic field. Benchmark studies include oxygen and nitrogen K-edge X-ray magnetic circular dichroism spectroscopy (XMCD) for closed-shell organic compounds, as well as L-edge XMCD spectroscopy for the high-spin open-shell transition metal ion Mn 2+ and the tetrahedral Mn(II)O 4 6– complex.

Chemical calculations↗
NASA NTRS1977

Observations of neutral composition and related ionospheric variations during a magnetic storm in February 1974

The neutral-atmosphere composition experiment on Atmosphere Explorer C measured N2, O, Ar, and He densities during a magnetic storm at altitudes down to about 160 km. At latitudes above 45 deg N, N2 and Ar densities generally increase during the storm, while He and O densities decrease. Below 45 deg N all densities tend to increase during the storm. The density increases at perigee indicate that density- or temperature-profile changes are taking place below 160 km. The return to prestorm conditions is very slow, demonstrating the integrating effect of the atmospheric response. A recent theoretical model incorporating thermospheric circulation and diffusion effects reproduces the longitudinally averaged data, including latitude trends and the asymmetry about the storm maximum. Comparison with the mass-spectrometer and incoherent-scatter empirical model shows qualitative agreement with latitude trends but not with storm asymmetry, while the earlier J71 model based on total mass density is not in agreement with observed latitudinal trends. A close correlation is found between in situ O/N2 measurements and in situ and ground-based ionosonde measurements of electron density.

Hedin, A. E.↗
NASA NTRS1988

Systematic variation of magnetic-field penetration depth in high-T(c) superconductors studied by muon spin relaxation

The muon relaxation rate (sigma) was measured in the high critical temperature superconductors YBa2Cu3O(x) for x = 6.66, 6.95, 7.0, and La1.85 Sr0.15 CuO4 in transverse external magnetic fields 1 is approximately 4kG. A simple relation is found which connects the transition temperature T(c), the magnetic field penetration depth lambda(L), the carrier concentration n(s) and the effective mass m* as T(c) varies as sigma which varies as 1/lambda(L) squared which varies as n(s)/m*. The linear dependence T(c) varies as n(s)/m* suggests a high energy scale for the coupling between superconducting carriers.

Uemura, Y. J.↗
NASA NTRS1988

Systematic variation of magnetic-field penetration depth in high-Tc superconductors studied by muon-spin relaxation

The muon relaxation rate (sigma) was measured in the high critical temperature superconductors YBa2Cu3O(x) for x = 6.66, 6.95, 7.0, and La1.85 SrO.15 CuO4 in transverse external magnetic fields 1 is approximately 4 kG. A simple relation is found which connects the transition temperature T(c), the magnetic field penetration depth lambda(L), the carrier concentration n(s) and the effective mass m* as T(c) varies as sigma which varies as 1/lambda(L) squared which varies as n(s)/m*. The linear dependence T(c) varies as n(s)/m* suggests a high energy scale for the coupling between superconducting carriers.

Uemura, Y. J.↗
NASA NTRS1992

Topological variation in the magnetic field line at the dayside magnetopause

This paper uses normal mode analysis to examine topological changes in magnetic field lines at the magnetopause. For a modified Harris sheet, the normal modes include a symmetric solution (tearing mode) and an antisymmetric solution (twisting mode). Both modes form flux ropes. The tearing mode in the presence of shear flow is studied. By modeling the external region plasma with drift kinetic formalism, the growth rate of the tearing mode is found to be reduced by shear flow. On the other hand, the shear flow generates a Kelvin-Helmholtz instability which makes the magnetic field perturbation a twisting mode structure. When magnetopause parameters are used, it is difficult to induce a tearing mode in the presence of shear flow, though a shear flow twisting mode did grow under these conditions.

Wang, Zhi↗
NASA NTRS1993

Long-term variations of interplanetary magnetic field spectra with implications for cosmic ray modulation

The paper calculates yearly averaged power spectra of interplanetary magnetic field turbulence at 1 AU over the period 1965-1988 for fluctuations in the frequency range 5.8 x 10 exp -6 to 4.6 x 10 exp -5 Hz, corresponding to periods of 6-48 hr. The amplitudes of the spectra vary with the sunspot cycle and are inversely correlated with the intensity of about 10-GeV cosmic rays. The observed spectra are used to calculate a lower limit to the cosmic ray scattering mean free path employing resonant magnetostatic quasi-linear theory for both 'slab' and isotropic geometries of the turbulence. The mean free paths thus obtained are typically about 0.1 AU in the slab model and about 0.3 AU in the isotropic model, but they are not significantly correlated with the modulated galactic cosmic ray intensity recorded by neutron monitors. It is inferred that the scattering processes described by resonant magnetostatic theory play, at best, a very minor role in the solar modulation of about 10-GeV cosmic rays.

Bieber, John W.↗