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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Modification of the Loss Cone for Energetic Particles in the Earth's Inner Magnetosphere

The behavior of energetic particles in the Earth's dipole and stretched magnetic-field models is explored with a focus on the shift of the atmospheric loss cone away from the magnetic-field direction and on non-adiabatic behavior occurring when the particle gyroradius becomes comparable with the gradient scale length of the local magnetic field. It is shown that the equatorial loss cone is aberrated away from the magnetic-field direction (pitch angle of 0°) by the perpendicular drift of a charged particle (which is referred to as the “Mozer transform” described in Mozer (1966, https://doi.org/10.1029/JZ071i011p02701). It is found that the Mozer coordinate transformation in pitch-angle/gyrophase-angle space better organizes the behavior of bounce times, mirror altitudes, drift speeds, and first adiabatic invariant. It also describes the loss-cone shift accurately for a certain range of values of the adiabaticity parameter ϵ, defined by the ratio of the particle gyroradius to the local radius of curvature of the magnetic field. For particles with larger ϵ, the Mozer transform (evaluated with the standard gradient-curvature drift) breaks down and the “central trajectory” theory can be used to calculate the angular shift of the loss cone, which now includes an Earthward shift. When ϵ becomes relatively large, stochastic field line curvature (FLC) scattering occurs: we show the intimate connection between the strength of FLC scattering and the loss-cone shift. Finally, by comparing ion orbits in the dipole and Tsyganenko (Ts89 and Ts04) magnetic fields, we conclude that the loss cone of ring-current ions is significantly modified during geomagnetically active times.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1979

A kinetic approach to magnetospheric modeling

The earth's magnetosphere is caused by the interaction between the flowing solar wind and the earth's magnetic dipole, with the distorted magnetic field in the outer parts of the magnetosphere due to the current systems resulting from this interaction. It is surprising that even the conceptually simple problem of the collisionless interaction of a flowing plasma with a dipole magnetic field has not been solved. A kinetic approach is essential if one is to take into account the dispersion of particles with different energies and pitch angles and the fact that particles on different trajectories have different histories and may come from different sources. Solving the interaction problem involves finding the various types of possible trajectories, populating them with particles appropriately, and then treating the electric and magnetic fields self-consistently with the resulting particle densities and currents. This approach is illustrated by formulating a procedure for solving the collisionless interaction problem on open field lines in the case of a slowly flowing magnetized plasma interacting with a magnetic dipole.

Whipple, E. C., Jr.↗
NASA NTRS2016

Turbulence Heating ObserveR: - Satellite Mission Proposal

The Universe is permeated by hot, turbulent, magnetized plasmas. Turbulent plasma is a major constituent of active galactic nuclei, supernova remnants, the intergalactic and interstellar medium, the solar corona, the solar wind and the Earths magnetosphere, just to mention a few examples. Energy dissipation of turbulent fluctuations plays a key role in plasma heating and energization, yet we still do not understand the underlying physical mechanisms involved. THOR is a mission designed to answer the questions of how turbulent plasma is heated and particles accelerated, how the dissipated energy is partitioned and how dissipation operates in different regimes of turbulence. THOR is a single-spacecraft mission with an orbit tuned to maximize data return from regions in near-Earth space magnetosheath, shock, foreshock and pristine solar wind featuring different kinds of turbulence. Here we summarize the THOR proposal submitted on 15 January 2015 to the Call for a Medium-size mission opportunity in ESAs Science Programme for a launch in 2025 (M4). THOR has been selected by European Space Agency (ESA) for the study phase.

Vaivads, A.↗
NASA NTRS1975

Low energy particle composition

A review is given of current knowledge of low-energy cosmic ray particles produced in the solar system. It is argued that the notion that the sun alone can accelerate particles in the solar system must be abandoned in light of evidence that Jupiter and earth may be sources of observed low-energy particles. Measurements of the composition and energy spectra of low-energy particles during quiet times are examined, emphasizing the abundance of protons and helium and of anomalous N, O, and Ne. The abundance of heavy particles (B, C, N, O, Ne, Ca and Fe) of unknown origin in the earth magnetosphere is examined. Reported observations of Jovian electrons are discussed and solar particle events with anomalous compositions (He-3 rich events and Fe rich events) are treated in detail. Nuclear abundances of solar particles, emphasizing their temporal and spatial variations are considered together with the nature of nuclear reaction products in solar flares.

Gloeckler, G.↗
NASA NTRS1981

Absorption and emission of extraordinary-mode electromagnetic waves near cyclotron frequency in nonequilibrium plasmas

An investigation is presented of two cases: (1) weakly relativistic electrons with a loss-cone type distribution, and (2) electrons with a drift velocity parallel to the ambient magnetic field. Numerical computations are given for physical parameters close to those in the polar region of the earth magnetosphere and laboratory experiments, with attention to the fast extraordinary-mode radiation whose frequency is near that of the electron cyclotron frequency. The fast extraordinary mode can escape from a strong field region to the weaker field region and may therefore be measured outside the plasma. It is found that the X mode radiation can be amplified by means of a cyclotron maser effect when the electrons have a loss-cone distribution, and it is concluded that, when the electron energy is sufficiently high, the X mode cutoff frequency may be lower than the cyclotron frequency.

Wu, C. S.↗
NASA NTRS1981

The aurora - An electrical discharge phenomenon surrounding the earth

An attempt to model the processes underlying the appearance of auroral phenomena as a chain of events beginning with power production and resulting in auroral light emissions is presented. Power is produced by the interaction of the solar wind with the earth magnetosphere, creating a dynamo effect which is a function of the solar wind speed and the magnitude and orientation of the solar wind magnetic field. The dynamo power generates the convective motion of magnetospheric plasma, and subsequent magnetic-field aligned currents communicate the dynamo power to the polar ionosphere. The currents close as Pederson currents, and the associated Lorentz force accelerates the ionosphere in the direction of the convective motion. An electric potential structure develops at a few thousand km height, forcing current-carrying electrons to flow down the field lines to the ionosphere, where interactions with atmospheric constituents create auroral displays.

Akasofu, S.-I.↗
NASA NTRS1982

Reverse draping of magnetic field lines in the boundary layer

An unexpected orientation of field lines has been found by ISEE satellite measurements of the earth magnetosphere boundary layer, perhaps indicating a reverse draping. Three-dimensional plasma flow measurements by ISEE 1 and 2 show the tailward flow in the boundary layer to have an equatorward component which suggests high-latitude plasma entry. Simultaneous magnetic field measurements with the two satellites during a boundary crossing sequence yielded data on the boundary layer electric currents and the boundary layer interface with plasma sheet and magnetosheath. The currents are found to be largely field-aligned, with intensities in the 0.03-0.06 microampere/sq m range.

Hones, E. W., Jr.↗
NASA NTRS1985

Structure of the plasmapause from ISEE 1 low-energy ion and plasma wave observations

Low-energy ion pitch angle distributions are compared with plasma density profiles in the near-earth magnetosphere using ISEE 1 observations. The classical plasmapause determined by the sharp density gradient is not always observed in the dayside region, whereas there almost always exists the ion pitch angle distribution transition from cold, isotropic to warm, bidirectional, field-aligned distributions. In the nightside region the plasmapause density gradient is typically found, and it normally coincides with the ion pitch angle distribution transition. The sunward motion of the plasma is found in the outer part of the 'plasmaspheric' plasma in the dusk bulge region.

Nagai, T.↗
NASA NTRS1984

Magnetic reconnection in space and laboratory plasmas; Proceedings of the Chapman Conference on Magnetic Reconnection, Los Alamos, NM, October 3-7, 1983

The physics of magnetic reconnection is discussed in reviews and reports of theoretical and experimental investigations. Topics examined include the theory of magnetic reconnection, reconnection in astronomical objects, reconnection in the earth magnetosphere and magnetotail, computer modeling, and laboratory plasmas. Diagrams, spectra, drawings, graphs, and photographs are provided.

Hones, E. W., Jr.↗