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Results for “GEOMAGNETIC EFFECT”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Circulation of the polar thermosphere during geomagnetically quiet and active times as observed by Dynamics Explorer 2

The effects of geomagnetic activity on the circulation of the high-latitude neutral thermosphere were studied for the periods of November 1981 through January 1982 and November 1982 through January 1983, using neutral wind measurements obtained by the Fabry-Perot interferometer and the wind and temperature spectrometer on the Dynamics Explorer 2. Results for the Northern Hemisphere show evidence of two-cell circulation of the thermosphere at high latitudes during both quiet and active geomagnetic periods at solar maximum; the dusk cell was always dominant. In the Southern Hemisphere, only a single circulation cell existed for both quiet and active periods associated with the dusk cell of ionospheric convection. In both hemispheres, the cell sizes decreased when geomagnetic activity was reduced.

Mccormac, F. G.↗
NASA NTRS1972

Geomagnetic field distortions and their effects on radiation belt particles.

One of the quadrupole terms in the main geomagnetic field is found to contribute to a north-south 'shear distortion' of the particle-drift shells, whereas one of the octupole components causes a longitude-dependent radial deformation and associated 'drift-shell splitting.' The collective action of all higher multipoles on trapped-particle motion is then used to analyze the 'true' anomalies or distortions of the internal geomagnetic field that are independent of the quadrupole-related eccentricity of the main dipole. These 'true' anomalies must originate in upper-mantle or crustal perturbations that lie relatively near the earth's surface on both sides of the mid-Atlantic ridge; they influence trapped-particle drift shells only where the latter have their closest approach to the earth (South Atlantic and South African areas). The quadrupole and octupole perturbations, on the other hand, obviously originate deep in the earth's core. In the final part of this review, we discuss the effects of external magnetospheric currents. A time-dependent symmetric ring current causes drift shells to be displaced radially, with associated particle acceleration; magnetopause currents introduce a day-night asymmetry, causing shell splitting.

Roederer, J. G.↗
DOE OSTI2025

Computational Analysis and Optimized Modeling of Geomagnetically Induced Currents in Power Transformers

In this project we aim to better understand the effect of geomagnetically induced currents (GIC) on power transformers. Expanding upon our previous work focused on producing a methodology for accuracy-enhanced computation of GIC signatures (i.e., time-domain current magnitude variation for the event duration) from a combination of physics-based and data-driven computational tools, we propose the use of these GIC signatures as inputs for a physically-detailed and optimized model of the power transformer to investigate how GIC determination and transformer modeling influence the evaluation of GIC effects on the transformer operation, as well as in its interaction with the power grid.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1974

Observations of interactions between interplanetary and geomagnetic fields

Magnetospheric effects associated with variations of the north-south component of the interplanetary magnetic field (IMF) are examined in light of recent experimental and theoretical results. Although the occurrence of magnetospheric substorms is statistically related to periods of southward IMF, the details of the interaction are not understood. In particular, attempts to separate effects resulting directly from the interaction between interplanetary and geomagnetic fields from those associated with substorms have produced conflicting results. It is possible, however, to say with some assurance that the transfer of magnetic flux from the dayside to the nightside magnetosphere, as evidenced by equatorward motion of the polar cusp and increases of the magnetic energy density in the lobes of the geomagnetic tail, is a direct consequence of the southward IMF. On the other hand, the formation of a macroscopic X-type neutral line at tail distances less than 35 earth radii appears to be a substorm phenomenon.

Burch, J. L.↗
NASA NTRS1990

Cosmic ray proton spectra at low rigidities

The cosmic ray proton rigidity spectra have been investigated with data collected in the Low Energy Antiproton (LEAP) balloon flight experiment flown from Prince Albert, Canada in 1987. The LEAP apparatus was designed to measure antiprotons using a superconducting magnet spectrometer with ancillary scintillator, time-of-flight, and liquid Cherenkov detectors. After reaching float altitude the balloon drifted south and west to higher geomagnetic cutoffs. The effect of the changing geomagnetic cutoff on the observed spectra was observed during analysis of the proton data along the balloon trajectory. This is the first measurement of the primary and splash albedo spectra over a wide rigidity range (few hundred MV to about 100 GV) with a single instrument.

Seo, E. S.↗
NASA NTRS1973

Observations of interactions between interplanetary and geomagnetic fields

Magnetospheric effects associated with variations of the north-south component of the interplanetary magnetic field are examined in light of recent recent experimental and theoretical results. Although the occurrence of magnetospheric substorms is statistically related to periods of southward interplanetary magnetic field, the details of the interaction are not understood. In particular, attempts to separate effects resulting directly from the interaction between the interplanetary and geomagnetic fields from those associated with substorms have produced conflicting results. The transfer of magnetic flux from the dayside to the nightside magnetosphere is evidenced by equatorward motion of the polar cusp and increases of the magnetic energy density in the lobes of the geomagnetic tail. The formation of a macroscopic X-type neutral line at tail distances less than 35 R sub E appears to be a substorm phenomenon.

Burch, J. L.↗
NASA NTRS1993

The effects of neutral inertia on ionospheric currents in the high-latitude thermosphere following a geomagnetic storm

Neutral flywheel effects are investigated in NCAR-TIGCM simulation of geomagnetic storms that occurred in November 23, 1982 and December 7-8, 1982. Theoretical calculations from the latter storm are compared with measurements of currents form instruments on the Dynamics Explorer 2 satellite. It is concluded that neutral flywheel effects can make a contribution to high latitude electrodynamics for a few hours after the main phase of a geomagnetic storm. The Hall currents that are driven by neutral winds during B(Z) northward conditions are generally in the opposite direction to those that occur during B(Z) southward conditions, when they are driven primarily by ion winds. The morphology of the field-aligned current system calculated by the NCAR-TIGCM during southward B(Z) conditions is in general agreement with observations.

Deng, W.↗
NASA NTRS1993

Simulation Of Fluctuating Geomagnetic Index

Mathematical model produces synthetic geomagnetic-index (ap) data including short-term fluctuations like those of real ap data. Measures geomagnetic activity computed from measurements of fluctuations in geomagnetic field taken at 12 high-latitude stations every 3 hours. Used in studies of interactions between solar wind and Earth, especially in studies of effect of geomagnetic field upon heating of thermosphere by impacts of energetic charged solar-wind particles.

Vedder, John↗
NASA NTRS1963

Indices of solar activity, appendix 6

Indices of solar & geomagnetic activity, variation of earth magnetic field in time & space, & field variation in magnetic storm

SOLAR ACTIVITY EFFECT↗