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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

MAGNETOSPHERIC ACCRETION AND EJECTION OF MATTER IN RESISTIVE MAGNETOHYDRODYNAMIC SIMULATIONS

The ejection of matter in the close vicinity of a young stellar object is investigated, treating the accretion disk as a gravitationally bound reservoir of matter. By solving the resistive MHD equations in two-dimensional axisymmetry using our version of the Zeus-3D code with newly implemented resistivity, we study the effect of magnetic diffusivity in the magnetospheric accretion-ejection mechanism. Physical resistivity was included in the whole computational domain so that reconnection is enabled by the physical as well as the numerical resistivity. We show, for the first time, that quasi-stationary fast ejecta of matter, which we call micro-ejections, of small mass and angular momentum fluxes, can be launched from a purely resistive magnetosphere. They are produced by a combination of pressure gradient and magnetic forces, in the presence of ongoing magnetic reconnection along the boundary layer between the star and the disk, where a current sheet is formed. The mass flux of micro-ejection increases with increasing magnetic field strength and stellar rotation rate, and is not dependent on the disk to corona density ratio and amount of resistivity.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1987

Remarks on the MHD problem of generic magnetospheres and magnetotails

An understanding of the plasma physics problem of MHD flow around a magnetized sphere or cylinder in different Reynolds number regimes is shown to be crucial to magnetospheric and magnetotail studies. A significant amount of knowledge can be acquired from experimental and computational hydrodynamic precedents. It is believed that highly symmetric laminar models of the magnetosphere and magnetotail are unlikely in view of the high Reynolds numbers involved.

Montgomery, D.↗
DOE OSTI2014

Nonlinear electric field structures in the inner magnetosphere

Recent observations by the Van Allen Probes spacecraft have demonstrated that a variety of electric field structures and nonlinear waves frequently occur in the inner terrestrial magnetosphere, including phase space holes, kinetic field-line resonances, nonlinear whistler-mode waves, and several types of double layer. However, it is nuclear whether such structures and waves have a significant impact on the dynamics of the inner magnetosphere, including the radiation belts and ring current. To make progress toward quantifying their importance, this study statistically evaluates the correlation of such structures and waves with plasma boundaries. A strong correlation is found. These statistical results, combined with observations of electric field activity at propagating plasma boundaries, are consistent with the identification of these boundaries as the source of free energy responsible for generating the electric field structures and nonlinear waves of interest. Therefore, the ability of these structures and waves to influence plasma in the inner magnetosphere is governed by the spatial extent and dynamics of macroscopic plasma boundaries in that region.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Ion acoustic solitons and supersolitons in a magnetized plasma with nonthermal hot electrons and Boltzmann cool electrons

Arbitrary amplitude, ion acoustic solitons, and supersolitons are studied in a magnetized plasma with two distinct groups of electrons at different temperatures. The plasma consists of a cold ion fluid, cool Boltzmann electrons, and nonthermal energetic hot electrons. Using the Sagdeev pseudo-potential technique, the effect of nonthermal hot electrons on soliton structures with other plasma parameters is studied. Our numerical computation shows that negative potential ion-acoustic solitons and double layers can exist both in the subsonic and supersonic Mach number regimes, unlike the case of an unmagnetized plasma where they can only exist in the supersonic Mach number regime. For the first time, it is reported here that in addition to solitions and double layers, the ion-acoustic supersoliton solutions are also obtained for certain range of parameters in a magnetized three-component plasma model. The results show good agreement with Viking satellite observations of the solitary structures with density depletions in the auroral region of the Earth's magnetosphere.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1974

Is Jupiter's magnetosphere like a pulsar's or earth's?

The application of pulsar physics to determine the magnetic structure in the planet Jupiter outer magnetosphere is discussed. A variety of theoretical models are developed to illuminate broad areas of consistency and conflict between theory and experiment. Two possible models of Jupiter's magnetosphere, a pulsar-like radial outflow model and an earth-like convection model, are examined. A compilation of the simple order of magnitude estimates derivable from the various models is provided.

Kennel, C. F.↗
DOE OSTI2017

The Warm Plasma Composition in the Inner Magnetosphere during 2012–2015

Ionospheric heavy ions play an important role in the dynamics of Earth's magnetosphere. The greater mass and gyro radius of ionospheric oxygen differentiates its behavior from protons at the same energies. Oxygen may have an impact on tail reconnection processes, and it can at least temporarily dominate the energy content of the ring current during geomagnetic storms. At sub-keV energies, multi-species ion populations in the inner magnetosphere form the warm plasma cloak, occupying the energy range between the plasmasphere and the ring current. Lastly, cold lighter ions from the mid-latitude ionosphere create the co-rotating plasmasphere whose outer regions can interact with the plasma cloak, plasma sheet, ring current, and outer electron belt. Here in this paper we present a statistical view of warm, cloak-like ion populations in the inner magnetosphere, contrasting in particular the warm plasma composition during quiet and active times. We study the relative abundances and absolute densities of warm plasma measured by the Van Allen Probes, whose two spacecraft cover the inner magnetosphere from plasmaspheric altitudes close to Earth to just inside geostationary orbit. We observe that warm (>30 eV) oxygen is most abundant closer to the plasmasphere boundary whereas warm hydrogen dominates closer to geostationary orbit. Warm helium is usually a minor constituent, but shows a noticeable enhancement in the near-Earth dusk sector.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1998

Modeling the Plasmasphere

The plasmasphere has often been considered one of the more boring regions in the magnetosphere. Its low energy plasma doesn't begin to compete against the free sources of energy available in the ring current, auroral zone, or plasma sheet. Its best known feature is its relatively highly density, archived as a result of prolonged accumulation of ionospheric outflow onto corotating flux tubes. On second look, however, the plasmasphere can be found to exhibit a remarkable influence on its more energetic cousins and display convection behavior indicative of physical processes acting throughout the magnetosphere for which we have no explanation. Plasmaspheric plasma densities and composition of heavy ions are particularly sensitive to heating by processes active in the ionosphere and all along field lines. Wave propagation and instabilities, collisional losses in the ring current, and heat transport from superthermal electrons are all equally sensitive to dense, heavy plasmaspheric densities and density gradients. It is in this context that we seek to characterize plasmaspheric populations using event based, empirical, and physical modeling methods. The modeling approaches, the challenges, and some of the results of these efforts will be presented.

Gallagher, Dennis L↗
NASA NTRS1973

Particle and field payloads

The capability of the Space Shuttle for the conduct of magnetospheric experiments is critically analyzed. Some physical problems are discussed on which a particle and field payload program could be based. They include the study of magnetospheric plasma processes, wave-particle interactions and auroral phenomena, both by artificial modification experiments and by systematic wide-scale observations of naturally occurring magnetospheric perturbation events.

Roederer, J. G.↗
DOE OSTI2022

The Critical Need for Innovations in Instruments and Techniques to Enable In-Situ Cold Ion and Cold Electron Measurements within the Magnetosphere

Relatively few studies have focused on the cold plasma populations of the magnetosphere due to difficulties associated with obtaining measurements. The cold particle populations are defined here as those with total energy approximately <100 eV which is an energy range for which measurements are difficult (regardless of species), but which often make up the bulk of the plasma density. These populations have known and suspected impacts on the structure and dynamics of the magnetosphere. Unfortunately, the lack of accurate measurements of the cold ion and cold electron populations through the magnetosphere makes closure of these science questions extremely difficult if not impossible. In a complex system of interconnected parts like the Earth’s magnetosphere, a lack of understanding of one part of the system (the cold electron and ion populations) is disabling. Hence, until cold electron and cold ion measurements are obtained robustly with every mission, the magnetospheric plasma environment cannot be completely understood. This will require innovations in plasma spectrometers and associated techniques required to obtain high-fidelity in-situ measurements of the cold ion and cold electron populations in the magnetosphere. This paper seeks to review the instruments and techniques that have been used to date and present possible options for future missions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

MAGNETAR GIANT FLARES-FLUX ROPE ERUPTIONS IN MULTIPOLAR MAGNETOSPHERIC MAGNETIC FIELDS

We address a primary question regarding the physical mechanism that triggers the energy release and initiates the onset of eruptions in the magnetar magnetosphere. Self-consistent stationary, axisymmetric models of the magnetosphere are constructed based on force-free magnetic field configurations that contain a helically twisted force-free flux rope. Depending on the surface magnetic field polarity, there exist two kinds of magnetic field configurations, inverse and normal. For these two kinds of configurations, variations of the flux rope equilibrium height in response to gradual surface physical processes, such as flux injections and crust motions, are carefully examined. We find that equilibrium curves contain two branches: one represents a stable equilibrium branch, and the other an unstable equilibrium branch. As a result, the evolution of the system shows a catastrophic behavior: when the magnetar surface magnetic field evolves slowly, the height of the flux rope would gradually reach a critical value beyond which stable equilibriums can no longer be maintained. Subsequently, the flux rope would lose equilibrium and the gradual quasi-static evolution of the magnetosphere will be replaced by a fast dynamical evolution. In addition to flux injections, the relative motion of active regions would give rise to the catastrophic behavior and lead to magnetic eruptions as well. We propose that a gradual process could lead to a sudden release of magnetosphere energy on a very short dynamical timescale, without being initiated by a sudden fracture in the crust of the magnetar. Some implications of our model are also discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Kinetic structures of quasi-perpendicular shocks in global particle-in-cell simulations

We carried out global Particle-in-Cell simulations of the interaction between the solar wind and a magnetosphere to study the kinetic collisionless physics in super-critical quasi-perpendicular shocks. After an initial simulation transient, a collisionless bow shock forms as a result of the interaction of the solar wind and a planet magnetic dipole. The shock ramp has a thickness of approximately one ion skin depth and is followed by a trailing wave train in the shock downstream. At the downstream edge of the bow shock, whistler waves propagate along the magnetic field lines and the presence of electron cyclotron waves has been identified. A small part of the solar wind ion population is specularly reflected by the shock while a larger part is deflected and heated by the shock. Solar wind ions and electrons are heated in the perpendicular directions. Ions are accelerated in the perpendicular direction in the trailing wave train region. This work is an initial effort to study the electron and ion kinetic effects developed near the bow shock in a realistic magnetic field configuration.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1985

Introduction to the Space Physics Analysis Network (SPAN)

The Space Physics Analysis Network or SPAN is emerging as a viable method for solving an immediate communication problem for the space scientist. SPAN provides low-rate communication capability with co-investigators and colleagues, and access to space science data bases and computational facilities. The SPAN utilizes up-to-date hardware and software for computer-to-computer communications allowing binary file transfer and remote log-on capability to over 25 nationwide space science computer systems. SPAN is not discipline or mission dependent with participation from scientists in such fields as magnetospheric, ionospheric, planetary, and solar physics. Basic information on the network and its use are provided. It is anticipated that SPAN will grow rapidly over the next few years, not only from the standpoint of more network nodes, but as scientists become more proficient in the use of telescience, more capability will be needed to satisfy the demands.

Green, J. L.↗
NASA NTRS2005

Solar Wind Fluctuations and Their Consequences on the Magnetosphere

Efforts have been made to extract the physical meaning of each term in our prediction model of the Dst index using the solar wind as the only input. The work has been published Journal of Geophysical Research (Temerin and Li, 21002). We found different terms in the model representing different current in the magnetospheric system and each current has different rise and decay times, with the symmetric ring current the slowest, then the partial ring current, then the tail current. We also have been trying to understand the physical meaning of the diffusion coefficient used in our prediction model of relativistic electron fluxes at geostationary orbit. The model reproduced the observations of MeV electron flux variations well, the diffusion coefficient had be assumed only die to local magnetic field fluctuations, leading to its 10th power dependence on the L. We have studied the theoretical derivation of the diffusion coefficient and we believe that the effect electric field fluctuations at smaller L could become more significant. We have expanded our previous radiation belt electron prediction model, which predicted MeV electron geosynchronous orbit based on solar wind measurements, to predict MeV electrons inside geosynchronous orbit. The model results are compared with measurements from Polar/CEPPAD. Prediction efficiencies of 0.56 and 0.54, respectively, at L=6 and L=4, have been achieved over the entire year of 1998. This work wa reported at 2003 Fall AGU and has been accepted for publication in Space Weather (Barker et al., 2005). We also have used simultaneous measurements of the upstream solar wind and of energetic electrons at geosynchronous orbit to analyze the response of electrons over a very wide energy range, 50 keV-6MeV, to solar wind variations. Enhancements of energetic electron fluxes over this whole energy range are modulated by the solar wind speed and the polarity of the interplanetary magnetic field (IMF). The solar wind speed seems to be a dominant controlling parameter for electrons of all energy. This work has been published in Space Weather (Li et al., 2005).

Li, Xin-Lin↗
DOE OSTI2012

Chorus wave amplification: A free electron laser in the Earth's magnetosphere

A new theoretical model for whistler-mode chorus amplification in the Earth's magnetosphere is presented. We derive, based on the free-electron laser mechanism in a high-gain amplifier, a new closed set of self-consistent relativistic equations that couple the Hamiltonian equations for particles with Maxwell's equations. We demonstrate that these equations predict, through a cubic equation, whistler amplification levels in good agreement with those observed in the Earth's magnetosphere.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2014

MMS Observatory TV Results Contamination Summary

The Magnetospheric Multiscale (MMS) mission is a constellation of 4 observatories designed to investigate the fundamental plasma physics of reconnection in the Earth's magnetosphere. The various instrument suites measure electric and magnetic fields, energetic particles, and plasma composition. Each spacecraft has undergone extensive environmental testing to prepare it for its minimum 2 year mission. In this paper, we report on the extensive thermal vacuum testing campaign. The testing was performed at the Naval Research Laboratory utilizing the "Big Blue" vacuum chamber. A total of ten thermal vacuum tests were performed, including two chamber certifications, three dry runs, and five tests of the individual MMS observatories. During the test, the observatories were enclosed in a thermal enclosure known as the "hamster cage". The enclosure allowed for a detailed thermal control of various observatory zone, but at the same time, imposed additional contamination and system performance requirements. The environment inside the enclosure and the vacuum chamber was actively monitored by several QCMs, RGA, and up to 18 ion gauges. Each spacecraft underwent a bakeout phase, which was followed by 4 thermal cycles. Unique aspects of the TV campaign included slow pump downs with a partial represses, thruster firings, Helium identification, and monitoring pressure spikes with ion gauges. Selected data from these TV tests is presented along with lessons learned.

Pressure↗
NASA NTRS1985

Particle behavior in the magnetosphere

The Rice Convection Model deals with large-scale processes in the earth's inner and middle magnetosphere, including coupling to the ionosphere. Starting from appropriate initial and boundary conditions, the model computes the following physical parameters: ionospheric electric fields and currents; magnetospheric particle distributions, electric fields, and electric currents; and magnetic-field-aligned (Birkeland) currents connecting the two regions. This paper evaluates work on the model, with emphasis on the assumptions made, the basic equations, and the numerical methods. The theoretical basis of the model is compared and contrasted with standard magnetohydrodynamics. The limitations imposed by the major assumptions are discussed. Model inputs and boundary conditions are listed, and the methods of specifying them discussed. Some physical conclusions and insights that have been gained from the model are listed and described very briefly. References are given to published discussions of the major points of physics.

Wolf, R. A.↗