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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 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Hiss or equatorial noise? Ambiguities in analyzing suprathermal ion plasma wave resonance

Previous studies have shown that low-energy ion heating occurs in the magnetosphere due to strong equatorial noise emission. Observations from the Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument recently determined that there was a depletion in the 1–10 eV ion population in the postmidnight sector of Earth during quiet times at L < 3. The diurnal variation of equatorially mirroring 1–10 eV H + ions at 2 < L < 3 is connected with similar diurnal variation in the electric field component of plasma waves ranging between 150 and 600 Hz. Measurements from the Van Allen Probes Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) data set are used here to analyze waves of this frequency in near-Earth space. However, when we examine the polarization of the waves in the 150 to 600 Hz range in the equatorial plane, the majority are right-hand polarized plasmaspheric hiss waves. The 1–10 eV H + equatorially mirroring population does not interact with right-hand waves, despite a strong statistical relationship suggesting that the two are linked. We present evidence supporting the relationship, both in our own work and the literature, but we ultimately conclude that the 1–10 eV H + heating is not related to the strong enhancement of 150 to 600 Hz waves.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1979

Scattering of terrestrial kilometric radiation at very high altitudes

On a number of occasions during the 3.5-yr operating lifetime of Rae 2, strong terrestrial kilometric radiation has been observed when the spacecraft was over the far side of the moon and when the low-altitude terrestrial magnetosphere was completely obscured from view. If these deep lunar occultation events are used to infer radio source locations, then it is found that the apparent source must sometimes be situated at geocentric distances of 10-40 earth-radii or more. From an analysis of these events, it is shown that they are probably due to propagation effects rather than the actual generation of the emission at such large distances. The kilometric radiation can be generated near the earth at auroral latitudes and subsequently strongly scattered in the magnetosheath and nearby solar wind to produce the large apparent distances. The most likely scatterers are density inhomogeneities in the magnetosheath plasma and ion plasma waves in the magnetosheath and the upstream solar wind.

Alexander, J. K.↗
NASA NTRS1987

Quadrennial review of the magnetotail

The findings of research conducted on the magnetotail in the years 1983-1986 are presented. The topics discussed include observations of the distant (between 60 and 220 earth radii) and the near-earth (earthward of 35 earth radii) magnetotail regions by the ISEE l, 2, and 3 and IMP 8 spacecraft, and magnetotail theory and modeling. These studies established the association between substorms and plasmoids in the deep tail and the linkage between the magnetosphere and the ionosphere via field-aligned currents and electric fields.

Huang, C. Y.↗
NASA NTRS1993

Collisionless shock structures of Earth and other planets

This report summarizes the closing segment of our multi-spacecraft, multi-instrument study of collisionless shock structure. In this last year of our study, we have necessarily concentrated on subjects that limited time and remaining resources could be expected to bring to reasonable stopping points, if not full conclusions. Our attention has been focused therefore on matters that were either well underway when the year began or that could be expected to yield rapidly completed reports publishable quickly in abbreviated versions. Contemporary publication delays prevent any new initiatives from reaching the literature within the year in the best of circumstances. The topics that fell into these categories were detailed plasma wave (pw) phenomenology in slow shocks in the Earth's distant geomagnetic tail, instantaneous orientations of theta(sub Bn) in quasiparallel (Q(sub parallel)) shock structure, and a comprehensive overview of the relationship between structural ULF waves in the Qll shock environment and waves in the magnetosphere, i.e. geomagnetic ULF pulsations. The remainder of this report describes our freshly completed results, discusses two related investigations of pw waves in the foreshock and magnetosheath, and appends the abstracts of published papers and the texts of papers in press.

Greenstadt, Eugene W.↗
NASA NTRS1977

Terrestrial kilometric radiation. II - Emission from the magnetospheric cusp and dayside magnetosheath

Measurements of the location of sources of terrestrial kilometric radiation obtained with the lunar-orbiting Radio Astronomy Explorer 2 satellite have revealed a class of emission associated with the cusp and dayside magnetosheath. At frequencies near 250 kHz, this emission is observed at radial distances between 2 and 20 earth radii at magnetic latitudes of 75 to 80 deg and is most often detected during periods of auroral activity and southward orientation of the interplanetary magnetic-field vertical component. During very disturbed times, the emission at the lowest frequencies (below about 200 kHz) appears to come from the dayside magnetosheath at distances of at least 12 earth radii. Whenever the geomagnetic dipole is tilted significantly with respect to the ecliptic pole, the cusp emission is confined to the hemisphere containing the subsolar point. The measurements also suggest that the region of cusp emission is rather narrowly confined in longitude to within a few hours of the noon meridian.

Alexander, J. K.↗
DOE OSTI2017

Can Substorm Particle Acceleration Be Applied to Solar Flares?

Using test particle studies in the electromagnetic fields of three-dimensional magnetohydrodynamic (MHD) simulations of magnetic reconnection, we study the energization of charged particles in the context of the standard two-ribbon flare picture in analogy to the standard magnetospheric substorm paradigm. In particular, we investigate the effects of the collapsing field (“collapsing magnetic trap”) below a reconnection site, which has been demonstrated to be the major acceleration mechanism that causes energetic particle acceleration and injections observed in Earth’s magnetotail associated with substorms and other impulsive events. We contrast an initially force-free, high-shear field (low beta) with low and moderate shear, finite-pressure (high-beta) arcade structures, where beta represents the ratio between gas (plasma) and magnetic pressure. We demonstrate that the energization affects large numbers of particles, but the acceleration is modest in the presence of a significant shear field. Without incorporating loss mechanisms, the effect on particles at different energies is similar, akin to adiabatic heating, and thus is not a likely mechanism to generate a power-law tail onto a (heated or not heated) Maxwellian velocity distribution.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1975

Certain regularities of geomagnetic and Baric fields at high latitudes

The existence of a relation between the variations of magnetic field at earth's surface in near-pole regions and the sector structure of the interplanetary magnetic field is considered as the evidence of the influence of the solar wind with its magnetic field on the processes proceeding in the magnetosphere. Two peculiarities between geomagnetic and interplanetary fields are discussed in detail: the north-south and spring-autumn asymmetry.

Mansurov, S. M.↗
NASA NTRS1975

Direct observations of the solar wind interaction with Jupiter

Pioneer 10 and Pioneer 11 plasma ion and electron observations in the vicinity of Jupiter are summarized. The data, obtained by the Ames Research Center Plasma Analyzer Experiments during the flybys of Jupiter in 1973 and 1974, indicate that the solar wind interaction with Jupiter (e.g., the formation of the Jovian bow shock, the magnetosheath, etc.) is basically similar to the solar wind interaction with the earth and only differs in terms of the scale size of the interaction. The plasma ion and electron measurements obtained on Pioneer 10 and Pioneer 11 are consistent with the proton measurements and indicate that the large, thick Jovian Magnetosphere which is inflated with a thermal plasma, is responsive to relatively minor changes in the solar wind dynamic pressure. The inferred motion of the Jovian bow shock and the speed at which it moved were strikingly similar during the Pioneer 10 and Pioneer 11 flybys.

Intriligator, D. S.↗
NASA NTRS1985

Three-dimensional plasma observations near the outer magnetospheric boundary

The present study is concerned with an evaluation of some of the plasma and field processes by which the magnetospheric boundary layer acts as a magnetohydrodynamic (HD) dynamo. An analysis is conducted of 18 crossings of the dayside magnetopause and boundary layer, taking into account data provided by the quadrispherical electrostatic analyzers (Lepedea) of the International Sun-Earth Explorer (ISEE) spacecraft. These instruments sample ion and electron velocity distributions in three dimensions. Attenion is given to aspects of data presentation, magnetopause identification, details regarding the magnetopause crossings, cross-field plasma flow, comparisons of magnetosheath and boundary layer plasma flow, and six conclusions.

Eastman, T. E.↗
NASA NTRS1995

Observation of a slow-mode shock in the dayside magnetopause reconnection layer

Plasma and magnetic field data from the International Sun Earth Explorer (ISEE) 2 spacecraft recorded on 29 Oct 1979 provide evidence for a slow shock (SS) in the reconnection layer of the dayside magnetopause. This layer is bounded on the magnetosheath side by the SS and on the magnetospheric side by a rotational discontinuity (RD). The direction of the accelerated plasma flow, the earthward sense of the normal magnetic field across both discontinuities, and the relative orientation of the SS and the RD all indicate that the reconnection site was located south of the spacecraft. Examination of the substantial pressure anisotropy downstream of the SS explains two unusual properties of the shock: (1) the slow-mode and intermediate-mode phase speeds are inverted downstream of the SS such that the RD propagates behind the SS rather than ahead of it; (2) the magnetic wave polarization reserves such that the SS initially displays a left-handed polarization and then switches to a right-handed polarization inside the shock structure.

Walthour, D. W.↗
NASA NTRS1998

Large-Scale Dynamics of the Magnetospheric Boundary: Comparisons between Global MHD Simulation Results and ISTP Observations

Understanding the large-scale dynamics of the magnetospheric boundary is an important step towards achieving the ISTP mission's broad objective of assessing the global transport of plasma and energy through the geospace environment. Our approach is based on three-dimensional global magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere- ionosphere system, and consists of using interplanetary magnetic field (IMF) and plasma parameters measured by solar wind monitors upstream of the bow shock as input to the simulations for predicting the large-scale dynamics of the magnetospheric boundary. The validity of these predictions is tested by comparing local data streams with time series measured by downstream spacecraft crossing the magnetospheric boundary. In this paper, we review results from several case studies which confirm that our MHD model reproduces very well the large-scale motion of the magnetospheric boundary. The first case illustrates the complexity of the magnetic field topology that can occur at the dayside magnetospheric boundary for periods of northward IMF with strong Bx and By components. The second comparison reviewed combines dynamic and topological aspects in an investigation of the evolution of the distant tail at 200 R(sub E) from the Earth.

Berchem, J.↗
NASA NTRS2000

Multimission Space and Solar Physics Microspacecraft

The solar fields and particles environment and its interaction with planetary magnetospheres are not only of considerable scientific interest, they can impact human endeavors as well.

microspacecraft space weather space physics solar ↗
NASA NTRS2011

Large Amplitude Whistlers in the Magnetosphere Observed with Wind-Waves

We describe the results of a statistical survey of Wind-Waves data motivated by the recent STEREO/Waves discovery of large-amplitude whistlers in the inner magnetosphere. Although Wind was primarily intended to monitor the solar wind, the spacecraft spent 47 h inside 5 R(sub E) and 431 h inside 10 R(sub E) during the 8 years (1994-2002) that it orbited the Earth. Five episodes were found when whistlers had amplitudes comparable to those of Cattell et al. (2008), i.e., electric fields of 100 m V/m or greater. The whistlers usually occurred near the plasmapause. The observations are generally consistent with the whistlers observed by STEREO. In contrast with STEREO, Wind-Waves had a search coil, so magnetic measurements are available, enabling determination of the wave vector without a model. Eleven whistler events with useable magnetic measurements were found. The wave vectors of these are distributed around the magnetic field direction with angles from 4 to 48deg. Approximations to observed electron distribution functions show a Kennel-Petschek instability which, however, does not seem to produce the observed whistlers. One Wind episode was sampled at 120,000 samples/s, and these events showed a signature that is interpreted as trapping of electrons in the electrostatic potential of an oblique whistler. Similar waveforms are found in the STEREO data. In addition to the whistler waves, large amplitude, short duration solitary waves (up to 100 mV/m), presumed to be electron holes, occur in these passes, primarily on plasma sheet field lines mapping to the auroral zone.

Kellogg, P. J.↗
DOE OSTI2015

Evolution of flux ropes in the magnetotail: A three-dimensional global hybrid simulation

Flux ropes in the Earth's magnetotail are widely believed to play a crucial role in energy transport during substorms and the generation of energetic particles. Previous kinetic simulations are limited to the local-scale regime, and thus cannot be used to study the structure associated with the geomagnetic field and the global-scale evolution of the flux ropes. Here, the evolution of flux ropes in the magnetotail under a steady southward interplanetary magnetic field are studied with a newly developed three-dimensional global hybrid simulation model for dynamics ranging from the ion Larmor radius to the global convection time scales. Magnetic reconnection with multiple X-lines is found to take place in the near-tail current sheet at geocentric solar magnetospheric distances x=−30R{sub E}∼−15R{sub E} around the equatorial plane (z=0). The magnetotail reconnection layer is turbulent, with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. A number of small-scale flux ropes are generated through the multiple X-line reconnection. The diameter of the flux ropes is several R{sub E}, and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several R{sub E} and does not extend across the entire section of the magnetotail, contrary to previous models and MHD simulation results and showing the importance of the three-dimensional effects. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of flux rope evolution: The small-scale flux ropes propagate earthward or tailward after formation, and eventually merge into the near-Earth region or the mid-/distant-tail plasmoid, respectively. During the propagation, some of the flux ropes can be tilted in the geocentric solar magnetospheric (x,y) plane with respect to the y (dawn-dusk) axis. Coalescence between flux ropes is also observed. At the same time, the evolution of the flux ropes in the multiple X-line reconnection layer can also lead to the acceleration and heating of ions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2008

Space Radiation Protection, Space Weather, and Exploration

Management of crew exposure to radiation is a major concern for manned spaceflight -- and will be even more important for the modern concept of longer-duration exploration. The inherent protection afforded to astronauts by the magnetic field of the Earth in Low Earth Orbit (LEO) makes operations on the space shuttle or space station very different from operations during an exploration mission. In order to experience significant radiation-derived Loss of Mission (LOM) or Loss of Crew (LOC) risk for LEO operations, one is almost driven to dictate extreme duration or to dictate an extreme sequence of solar activity. Outside of the geo-magnetosphere, however, this scenario changes dramatically. Exposures to the same event on the ISS and on the surface of the Moon may differ by multiple orders of magnitude. This change in magnitude, coupled with the logistical constraints present in implementing any practical operational mitigation make situational awareness with regard to space weather a limiting factor for our ability to conduct exploration operations. With these differences in risk to crew, vehicle and mission in mind, we present the status of the efforts currently underway as the required development to enable exploration operations. The changes in the operating environment as crewed operations begin to stretch away from the Earth are changing the way we think about the lines between "research" and "operations". The real, practical work to enable a permanent human presence away from Earth has already begun.

Zapp, Neal↗
NASA NTRS1989

Steady state magnetic field configurations for the earth's magnetotail

A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).

Hau, L.-N.↗
NASA NTRS1974

In-situ observations of irregular ionospheric structure associated with the plasmapause

Additional studies of the ion composition results obtained from the OGO-6 satellite support earlier observations of irregularities in the distribution of H(+) and He(+) within the light ion trough near L = 4, which has been associated with the plasmapause. These irregularities are in the form of sub-troughs superimposed upon the major midlatitude decrease of the light ions. In the sub-troughs, ionization depletions and recoveries of as much as an order of magnitude are observed within a few degrees of latitude, usually exhibited in a pattern which changes significantly with longitude as the earth rotates beneath the relatively fixed satellite orbit. The location and properties exhibited by these sub-troughs appear to be consistent with the concept of a plasmasphere distortion in the form of 'plasmatails' resulting from the combined effects of magnetospheric convection plus corotation.

Taylor, H. A., Jr.↗