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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Off-Line-of-Sight Propagation Effects on Geomagnetic EMP from High-Altitude Bursts

The three-dimensional geometry associated with off-line-of-sight gamma emission in high-altitude bursts causes delays between creation of ionization and EMP arrival along the propagation path to the ground observer. These delays make the conductivity experienced by the EMP a function of the gamma emission angle. Legacy EMP codes, such as CHAP, are one-dimensional and cannot treat this EMP arrival delay. Comparison of CHAP calculations with those using the author’s three-dimensional MACSYNC code show significant differences in amplitude and shape of the computed EMP. Thus use of CHAP appears inadvisable for National security applications of EMP relying on detailed knowledge of the field. New codes solving Maxwell’s equations in three dimensions, being developed by the EMP community, ought to be used instead.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
NASA NTRS1961

Solar Influences on Geomagnetic and Related Phenomena

A discussion of the geomagnetic effects of streams of electromagnetic and particular radiation from the sun. The interplay of forces between the geomagnetic field and solar streams is outlined; and the theoretical relationship between these, the solar storms, the trapped Van Allen radiations, the polar aurora, and geomagnetic field distortion are presented.

Vestine, E. H.↗
NASA NTRS1974

International Cosmic Ray Conference, 13th, University of Denver, Denver, Colo., August 17-30, 1973, Proceedings. Volumes 1 & 2

Topics discussed include diffuse gamma rays, gamma ray sources (in particular, the Crab Nebula and Crab Pulsar), X-ray sources, isotopic and nuclear composition, spectra of nuclei, searches for antinuclei, studies of VH and VVH nuclei, measurements of electrons and positrons, the spectra of high-energy electrons, cosmic gamma rays, cosmic ray sources, interplanetary radial gradients, the theory and observation of electron modulation, short-period cosmic ray intensity variations, atmospheric and coupling effects on neutron monitors and muon telescopes, secondary particles and photons in the atmosphere, harmonics of diurnal variations, geomagnetic effects and cutoffs, planetary and interplanetary effects, solar particle access observations, long-term cosmic ray intensity modulation by solar activity and interplanetary effects, Forbush decreases, modulation and anisotropy of low-energy particles, the theory and models of solar particle propagation, solar flare particle composition, and relativistic solar particles. Individual items are announced in this issue.

Source record↗
NASA NTRS1972

Discontinuities and shock waves in the interplanetary medium and their interaction with the magnetosphere.

The discontinuous structure of the solar wind is described with emphasis on properties related to geomagnetic impulses. Some of the discontinuities are clearly hydromagnetic shocks and tangential discontinuities, and can produce a significant change in the momentum flux at the magnetosphere boundary. Such a change generates an impulse which propagates through the magnetosphere to the earth where it is observed world-wide as an impulse in magnetograms. The propagation process is not reviewed here, but the relation between the initial cause (discontinuity) and the final effect (geomagnetic impulse) is reviewed in detail. The various types of impulses are examined, and are related qualitatively to the various types of discontinuities. The magnitude of an impulse is related to the change in the momentum flux. The propagation time and the rise time depend on the propagation process rather than on the initial state.

Burlaga, L. F.↗
DOE OSTI2015

Do solar cycles influence giant cell arteritis and rheumatoid arthritis incidence?

Our objective was to examine the influence of solar cycle and geomagnetic effects on the incidence of giant cell arteritis (GCA) and rheumatoid arthritis (RA). Methods: We used data from patients with GCA (1950-2004) and RA (1955-2007) obtained from population-based cohorts. Yearly trends in age-adjusted and sex-adjusted incidence were correlated with the F10.7 index (solar radiation at 10.7 cm wavelength, a proxy for the solar extreme ultraviolet radiation) and AL index (a proxy for the westward auroral electrojet and a measure of geomagnetic activity). Fourier analysis was performed on AL, F10.7, and GCA and RA incidence rates. Results: The correlation of GCA incidence with AL is highly significant: GCA incidence peaks 0-1 year after the AL reaches its minimum (ie, auroral electrojet reaches a maximum). The correlation of RA incidence with AL is also highly significant. RA incidence rates are lowest 5-7 years after AL reaches maximum. AL, GCA and RA incidence power spectra are similar: they have a main peak (periodicity) at about 10 years and a minor peak at 4-5 years. However, the RA incidence power spectrum main peak is broader (8-11 years), which partly explains the lower correlation between RA onset and AL. The auroral electrojets may be linked to the decline of RA incidence more strongly than the onset of RA. The incidences of RA and GCA are aligned in geomagnetic latitude. Conclusions: AL and the incidences of GCA and RA all have a major periodicity of about 10 years and a secondary periodicity at 4-5 years. Geomagnetic activity may explain the temporal and spatial variations, including east-west skewness in geographic coordinates, in GCA and RA incidence, although the mechanism is unknown. Lastly, the link with solar, geospace and atmospheric parameters need to be investigated. These novel findings warrant examination in other populations and with other autoimmune diseases.

58 GEOSCIENCES↗
NASA NTRS2006

Major Geomagnetic Storms (Dst less than or equal to -100 nT) Generated by Corotating Interaction Regions

Seventy-nine major geomagnetic storms (minimum Dst less than or equal to -100 nT) observed in 1996 to 2004 were the focus of a Living with a Star Coordinated Data-Analysis Workshop (CDAW) in March, 2005. In 9 cases, the storm driver appears to have been purely a corotating interaction region (CIR) without any contribution from coronal mass ejection-related material (interplanetary coronal mass ejections, ICMEs). These storms were generated by structures within CIRs located both before and/or after the stream interface that included persistently southward magnetic fields for intervals of several hours. We compare their geomagnetic effects with those of 159 CIRs observed during 1996 - 2005. The major storms form the extreme tail of a continuous distribution of CIR geoeffectiveness which peaks at Dst approx. -40 nT but is subject to a prominent seasonal variation of - 40 nT which is ordered by the spring and fall equinoxes and the solar wind magnetic field direction towards or away from the Sun. The O'Brien and McPherron [2000] equations, which estimate Dst by integrating the incident solar wind electric field and incorporating a ring current loss term, largely account for the variation in storm size. They tend to underestimate the size of the larger CIR-associated storms by Dst approx. 20 nT. This suggests that injection into the ring current may be more efficient than expected in such storms. Four of the nine major storms in 1996 - 2004 occurred during a period of less than three solar rotations in September - November, 2002, also the time of maximum mean IMF and solar magnetic field intensity during the current solar cycle. The maximum CIR-storm strength found in our sample of events, plus additional 23 probable CIR-associated Dst less than or equal to -100 nT storms in 1972 - 1995, is (Dst = -161 nT). This is consistent with the maximum storm strength (Dst approx. -180 nT) expected from the O'Brien and McPherron equations for the typical range of solar wind electric fields associated with CIRs. This suggests that CIRs alone are unlikely to generate geomagnetic storms that exceed these levels.

Richardson, I. G.↗
NASA NTRS1972

The physics of the neutral upper atmosphere.

Particular attention is given to models of the upper atmosphere that deal with the diurnal variation and the latitudinal density dependence. The upper atmosphere is considered as essentially an ideal gas, or rather a weakly ionized plasma, where physical and chemical processes of considerable complexity take place. The final goal for the theoretical models of the upper atmosphere is to derive the time and space dependence of the physical quantities density, composition, temperature, pressure, and state of motion by theoretical considerations from basic physical assumptions. Questions of the dynamics of the upper atmosphere are discussed together with one- and two-dimensional models of the upper atmosphere, three-dimensional models, the geomagnetic effect, and the semiannual density variation.

Blum, P.↗
NASA NTRS1973

The relation between the polarity of the interplanetary magnetic field and the polar geomagnetic field

The relation between the azimuthal component of the interplanetary magnetic field and the polar cap geomagnetic field is discussed. The geomagnetic effects can be described as produced by an ionospheric current system encircling the magnetic pole. The sense of the current is clockwise during toward-sectors and reversed during away-sectors. The importance of this very direct solar-terrestrial relation is stressed. A recent magnetic sunspot cycle model is discussed as inferred from this relationship, the basic feature being that the sun reproduces the same sector pattern during every sunspot cycle.

Svalgaard, L.↗
NASA NTRS1981

SAS 2 observations of the earth albedo gamma radiation above 35 MeV

The earth albedo gamma radiation above 35 MeV in the equatorial region is investigated using observations from the second Small Astronomy Satellite. The zenith angle distribution of the gamma radiation has a peak toward the horizon which is about an order of magnitude more intense than the radiation coming from the nadir, and nearly two orders of magnitude more intense than the gamma radiation from most parts of the sky. The gamma radiation originating from the western horizon is a factor of four more intense than the radiation from the eastern horizon and a factor of three more intense than that from the northern and southern directions. This reflects the geomagnetic effects on the incident cosmic rays whose interactions produce the albedo gamma rays. The variation of the upcoming gamma ray intensity with vertical cutoff rigidity is consistent with the empirical relationship found by Gur'yan et al. (1979).

Thompson, D. J.↗
NASA NTRS1985

Measurement of neutrino oscillations in MACRO experiment

The possibility of investigating neutrino oscillations in the proposed MACRO experiment are considered. Its sensitivity taking into account the theoretical uncertainties coming from flux calculations, geomagnetic effects and propagation through matter, and the experimental limitations.

Musser, J.↗
NASA NTRS1985

Comparison of the calibration of ionospheric delay in VLBI data by the methods of dual frequency and Faraday rotation

When both S-band and X-band data are recorded for a signal which has passed through the ionosphere, it is possible to calculate the ionospheric contribution to signal delay. In Very Long Baseline Interferometry (VLBI) this method is used to calibrate the ionosphere. In the absence of dual frequency data, the ionospheric content measured by Faraday rotation, using a signal from a geostationary satellite, is mapped to the VLBI observing direction. The purpose here is to compare the ionospheric delay obtained by these two methods. The principal conclusions are: (1) the correlation between delays obtained by these two methods is weak; (2) in mapping Faraday rotation measurements to the VLBI observing direction, a simple mapping algorithm which accounts only for changes in hour angle and elevation angle is better than a more elaborate algorithm which includes solar and geomagnetic effects; (3) fluctuations in the difference in total electron content as seen by two antennas defining a baseline limit the application of Faraday rotation data to VLBI.

Scheid, J. A.↗
NASA NTRS1986

Interplanetary shock collisions - Forward with reverse shocks

When one interplanetary shock overtakes another, the structure that results depends upon the nature of the interacting shocks. The results of collisions of forward with reverse shocks, in two dimensions, are numerically examined, and it is shown that the results depend primarily upon shock strength. It is also noted that such interactions could explain why many energy outburst on the sun that would be expected to cause geomagnetic effects at the earth, do not.

Smith, Z. K.↗