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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Note on the electric splitting of drift shells

A nonrelativistic analysis is presented for the deviation of a particle from its dipole magnetic drift shell in the presence of an electric field. An alternative definition of weak shell splitting is introduced in which the corotation drift velocity need not be small with respect to the azimuthal magnetic drift velocity. Approximate explicit solutions are obtained for the asymmetry of drift shells in the strong shell splitting case, i.e., for the case where the cross-magnetosphere potential drop is not small compared to particle kinetic energy. Upper limits to drift shell asymmetry are obtained from considerations of the Alfven layer.

Kivelson, M. G.↗
NASA NTRS1978

Engineering description of the OMS/RCS/DAP modes used in the HP-9825A High Fidelity Relative Motion Program (HFRMP)

Simplified mathematical models are reported for the space shuttle's Orbital Maneuvering System (OMS), Reaction Control System (RCS), and on-orbit Digital Autopilot (DAP) that have been incorporated in the High-Fidelity Relative Motion Program (HFRMP) for the HP-9825A desk-top calculator. Comparisons were made between data generated by the HFRMP and by the Space Shuttle Functional Simulator (SSFS), which models the cited shuttle systems in much greater detail. These data include propellant requirements for representative translational maneuvers, rotational maneuvers, and attitude maintenance options. Also included are data relating to on-orbit trajectory deviations induced by RCS translational cross coupling. Potential close-range stationkeeping problems that are suggested by HFRMP simulations of 80 millisecond (as opposed to 40 millisecond) DAP cycle effects are described. The principal function of the HFRMP is to serve as a flight design tool in the area of proximity operations.

Wilson, S. W.↗
NASA NTRS1984

An analysis of the high-latitude thermospheric wind pattern calculated by a thermospheric general circulation model. I - Momentum forcing

A diagnostic processor (DP) was developed for analysis of hydrodynamic and thermodynamic processes predicted by the NCAR thermospheric general circulation model (TGCM). The TGCM contains a history file on the projected wind, temperature and composition fields at each grid point for each hour of universal time. The DP assimilates the history file plus ion drag tensors and drift velocities, specific heats, coefficients of viscosity, and thermal conductivity and calculates the individual forcing terms for the momentum and energy equations for a given altitude. Sample momentum forcings were calculated for high latitudes in the presence of forcing by solar radiation and magnetospheric convection with a 60 kV cross-tail potential, i.e., conditions on Oct. 21, 1981. It was found that ion drag and pressure forces balance out at F region heights where ion drift velocities are small. The magnetic polar cap/auroral zone boundary featured the largest residual force or net acceleration. Diurnal oscillations were detected in the thermospheric convection, and geostrophic balance was dominant in the E layer.

Killeen, T. L.↗
NASA NTRS1986

Comment on electric field evidence on the viscous interaction at the magnetopause, by F. S. Mozer

In his paper on ISEE-1 electric field measurements in the low-latitude boundary layer (LLBL), Mozer (1984) concluded that LLBL contributes only about 10 percent of the average cross-tail potential difference Delta phi, and thus that viscous effects associated with the boundary layer are not very important as compared to the competing process of magnetic reconnection. Here, it is pointed out that Mozer may not have recognized an important feature of the LLBL, in that the maximum or minimum values of Delta phi (BL) may have occurred tailward of the spacecraft orbit. It is also pointed out that the sum of the viscous interaction potentials across the dawn and dusk low latitude boundary layers is closer to 30 kV than the 6 kV reported by Mozer. In his reply, Mozer gives reasons why the values he used are correct and that his earlier conclusions need no revision.

Heikkila, W. J.↗
NASA NTRS1986

Comments on 'Frontogenesis in a moist semigeostrophic model'

The development of narrow updrafts or jetlike features in the vertical motion field (VMF) over the leading edge of a surface frontal zone is examined on the basis of model simulations, summarizing and clarifying the results presented by Keyser and Anthes (1982) and responding to critical remarks by Mak and Bannon (1984). Typical velocity and potential-temperature cross sections are shown, and it is concluded that the inclusion of generally parameterized planetary-boundary-layer (PBL) physics in the model has a significant effect on the VMF, suggesting that frictional processes alone (without latent heating) can explain the formation of jetlike frontal updrafts. In a reply by Mak and Bannon it is argued that the increased strength of the VMF in models including PBL physics is not significant, whereas other models show that the VMF can be significantly strengthened and narrowed by condensational heating alone.

Keyser, D.↗
NASA NTRS1988

AMPTE/CCE observations of shell-like He(2+) and O(6+) distributions in the magnetosheath

Simultaneous observations of solar wind He(2+) and O(6+) shell-like distributions in the magnetosheath were obtained by the AMPTE CCE on November 1, 1984. It is found that the present distributions are centered on the downstream H(+) bulk velocity and have radii proportional to the mass/charge ratio. The results support an electrostatic cross-shock potential model.

Fuselier, S. A.↗
NASA NTRS1989

Observational results using the microwave temperature profiler during the Airborne Antarctic Ozone Experiment

The Microwave Temperature Profiler (MTP) measures profiles of air temperature versus altitude. The altitude coverage is about 5 km at a flight altitude of 20 km (66,000 feet), and the profiles are obtained every 14 s. The MTP instrument is installed on NASA's ER-2 aircraft, which flew 13 missions over Antarctica during the Airborne Antarctic Ozone Experiment. Altitude temperature profiles were used to derive potential temperature cross sections. These cross sections have been useful in detecting atmospheric waves. Many wave encounters have been identified as 'mountain waves'. The mountain waves are found to extend from the lowest altitudes measured to the highest (about 24 km). The southern part of the Palmer Peninsula was found to be associated with mountain waves more than half the time. Altitude temperature profiles were also used to measure the lapse rate along the flight track. Lapse rate versus latitude plots do not show significant changes at the ozone hole boundary.

Gary, Bruce L.↗
NASA NTRS1989

Electron acceleration at nearly perpendicular collisionless shocks. I - One-dimensional simulations without electron scale fluctuations

Under certain conditions electrons can be reflected and effectively energized at quasi-perpendicular shocks. This process is most prominent close to the point where the upstream magnetic field is tangent to the curved shock. A theoretical explanation of the underlying physical mechanism has been proposed which assumes conservation of magnetic moment and a static, simplified shock profile are performed. Test particle calculations of the electron reflection process in order to examine the results of the theoretical analysis without imposing these restrictive conditions. A one-dimensional hybrid simulation code generates the characteristic field variations across the shock. Special emphasis is placed on the spatial and temporal length scales involved in the mirroring process. The simulation results agree generally well with the predictions from adiabatic theory. The effects of the cross-shock potential and unsteadiness are quantified, and the influence of field fluctuations on the reflection process is discussed.

Krauss-Varban, D.↗
NASA NTRS1990

Spacelab 3 mission

Spacelab-3 (SL-3) was the first microgravity mission of extended duration involving crew interaction with animal experiments. This interaction involved sharing the Spacelab environmental system, changing animal food, and changing animal waste trays by the crew. Extensive microbial testing was conducted on the animal specimens and crew and on their ground and flight facilities during all phases of the mission to determine the potential for cross contamination. Macroparticulate sampling was attempted but was unsuccessful due to the unforseen particulate contamination occurring during the flight. Particulate debris of varying size (250 micron to several inches) and composition was recovered post flight from the Spacelab floor, end cones, overhead areas, avionics fan filter, cabin fan filters, tunnel adaptor, and from the crew module. These data are discussed along with solutions, which were implemented, for particulate and microbial containment for future flight facilities.

Dalton, Bonnie P.↗
NASA NTRS1995

The Earth's magnetosphere is 165 R(sub E) long: Self-consistent currents, convection, magnetospheric structure, and processes for northward interplanetary magnetic field

The subject of this paper is a self-consistent, magnetohydrodynamic numerical realization for the Earth's magnetosphere which is in a quasi-steady dynamic equilibrium for a due northward interplanetary magnetic field (IMF). Although a few hours of steady northward IMF are required for this asymptotic state to be set up, it should still be of considerable theoretical interest because it constitutes a 'ground state' for the solar wind-magnetosphere interaction. Moreover, particular features of this ground state magnetosphere should be observable even under less extreme solar wind conditions. Certain characteristics of this magnetosphere, namely, NBZ Birkeland currents, four-cell ionospheric convection, a relatively weak cross-polar potential, and a prominent flow boundary layer, are widely expected. Other characteristics, such as no open tail lobes, no Earth-connected magnetic flux beyond 155 R(sub E) downstream, magnetic merging in a closed topology at the cusps, and a 'tadpole' shaped magnetospheric boundary, might not be expected. In this paper, we will present the evidence for this unusual but interesting magnetospheric equilibrium. We will also discuss our present understanding of this singular state.

Fedder, J. A.↗
NASA NTRS1994

Recombination of H(3+) and D(3+) ions with electrons

Flowing-afterglow measurements in decaying H3(+) or D3(+) plasmas suggest that de-ionization does not occur by simple binary recombination of a single ion species. We find that vibrational excitation of the ions fails to provide an explanation for the effect, contrary to an earlier suggestion. Instead, we suggest that collisional stabilization of H3** Rydberg molecules by ambient electrons introduces an additional dependence on electron density. The proposed mechanism would permit plasma de-ionization to occur without the need for dissociative recombination by the mechanism of potential-surface crossings.

Johnsen, R.↗
NASA NTRS1995

Recombination of H3(+) and D3(+) Ions in a Flowing Afterglow Plasma

The analysis of flowing afterglow plasmas containing H3(+) or D3(+) ions indicates that the de-ionization of such plasmas does not occur by simple dissociative recombination of ions with electrons. An alternative model of de-ionization is proposed in which electrons are captured into H3(**) auto-ionization Rydberg states that are stabilized by collisional mixing of the Rydberg molecules' angular momenta. The proposed mechanism would enable de-ionization to occur without the need for dissociative recombination by the mechanisms of potential-surface crossings.

Gougousi, T.↗
NASA NTRS1997

Atmospheric Layers Measured from the NASA DC-8 During PEM-West B and Comparison with PEM-West A

The Pacific Exploratory Mission-West B (PEM-West B) explored atmospheric layer structure using measurements of O3, H2O, CO, and CH4 from the NASA DC-8 fast-response instruments. The mission took place in February-March 1994 over the western Pacific, mainly in the northern hemisphere. Results were compared with similar measurements made during the Pacific Exploratory Mission-West A (PEM-West A) in September-October 1991. PEM-West B sampled 94 vertical profiles, with an average atmospheric depth per profile of 6.4 km, and this sampling yielded 254 discrete layers. PEM-West A sampled 105 profiles, also with a 6.4 km average depth, yielding 538 layers. Both missions revealed that layers containing high ozone and low water vapor were the most abundant, and low ozone and high water vapor layers were the next most abundant. Lidar images and potential vorticity cross sections showed the former associated with subsidence from the stratosphere in middle latitudes, spreading into the tropics. The latter was associated with convection from the boundary layer. The partition among different types of layers only changed slightly in the two missions, although PEM-West B had half as many layers. Compared to PEM-West A, PEM-West B showed only one-third the number of layers associated with polluted continental air. However, PEM-West B revealed significantly more layers showing characteristics of descended clean marine air. In some cases these layers originated from the southern hemisphere. For ozone- and water-vapor-rich layers, the ozone deviation amplitude was higher in low latitudes and lower in high latitudes in PEM-West B. The mean thickness of layers increased from about 450 m in PEM-West A to 680 in in PEM-West B. Layers also existed in the Intertropical Convergence Zone. CO2 measurements had sufficient vertical resolution to show layer structure as well.

Wu, Zhongxiang↗
NASA NTRS2001

Magnetosphere-Regolith/Exosphere Coupling: Differences and Similarities to the Earth Magnetosphere-Ionosphere Coupling

Of the three Mercury passes made by Mariner 10, the first and third went through the Mercury magnetosphere. The third encounter which occurred during northward IMF (interplanetary magnetic field) showed quiet time magnetic fields. In contrast the third encounter observed clear substorm signatures including dipolarization, field-aligned currents (FACs) and injection of energetic electrons at geosynchronous orbit. However, the determined cross-tail potential drop and the assumed height integrated conductance indicate that the FAC should be 2-50 times weaker than observed. We address this inconsistency and the fundamental problem of FAC closure whether this takes place in the regolith or in the exosphere. The current state of knowledge of the magnetosphere-exosphere/regolith coupling is addressed and similarities and differences to the Earth magnetosphere-ionosphere coupling are discussed.

Gjerleov, J. W.↗
NASA NTRS2003

New ISTP Solar Max: A Multi-Spacecraft Study of the Flow of Ionospheric Plasma

The unique instrumentation on the Polar satellite combined with the simultaneous measurement of different parts of the magnetosphere with multiple satellites make possible the study of magnetospheric processes in a special way. In particular, the study of the ionospheric supply of plasma to the magnetosphere can by accomplished to give important results on the plasmas which drive the dynamics of the magnetosphere. This study concentrated on the period of September to December, 2001 in which the Polar orbit had precessed to the point that the line of apsides was near the equatorial plane. This unique orbital configuration enabled the TIDE instrument to measure outflowing ions across the polar cap and then transit the magnetotail lobes and observe the dramatic change in plasma characteristics as the satellite entered the plasma sheet. Contact was made with investigators on the Cluster and Geotail satellite missions and corresponding time frames were studied in the data. There were two approximate conjunctions between Polar and Geotail and data were compared to look for features which might be related. The higher energy concentration of the Geotail instrument made direct comparisons with TIDE difficult, and the Cluster measurements did not surface any cases that corresponded closely in space and time. There were, however, many interesting aspects of the Polar orbits which permitted the observation of the changing ionospheric outflowing plasma characteristics. As in earlier measurements, the ionospheric plasma could be seen flowing up the magnetic field lines out of the northern and southern polar caps. Its energy suggested a polar wind origin energized by the centrifugal acceleration of flow through the polar cusp. The roughly 10eV ions then moved out into the lobes of the magnetotail where they could be seen flowing toward the plasma sheet in both the northern and southern magnetotail lobes. There was also a double field-aligned region of warm ions observed just outside the plasmasphere, stretching toward the auroral zone and inner plasma sheet boundary. Upon entering the plasma sheet, the plasma energy jumped from 10 s of eV to greater than 1 keV. The single field aligned flows transitioned to highly variable spatially choppy energized ion distributions with a variety of pitch angle configurations. This pattern was quite repeatable in all of the Polar orbits that were examined and are compatible with the source of ions being the polar wind which is then energized to 10 s of eV by the centrifugal acceleration. These modestly energized polar wind ions are then carried to the magnetotail where they are substantially energized by the curvature drift-induced movement across the cross-tail potential of the magnetotail. This latter drift energizes the ions to the energies typically found in the plasma sheet. Subsequent drift and energization can cause the ions to become part of the ring current. The results of this study were presented at the Spring AGU meeting in 2002 and the GEM meeting in June 2003. They are the foundation for a paper that has been submitted by Matthew Huddleston to the Journal of Geophysical Research in December 2003. This work was part of the thesis that Matthew completed in finishing his Ph.D. in Physics at Vanderbilt University.

Chappell, Charles R.↗
NASA NTRS2005

Early immune response and regulation of IL-2 receptor subunits

Affymetrix oligonucleotide arrays were used to monitor expression of 8796 genes and probe sets in activated T-cells; analysis revealed that 217 genes were significantly upregulated within 4 h. Induced genes included transcription factors, cytokines and their receptor genes. Analysis by semi-quantitative RT-PCR confirmed the significant induction of IL-2, IL-2R(gamma) and IL-2R(alpha). Forty-eight of the 217 induced genes are known to or predicted to be regulated by a CRE promoter/enhancer. We found that T-cell activation caused a significant increase in CREB phosphorylation furthermore, inhibition of the PKC pathway by GF109203 reduced CREB activation by 50% and inhibition of the PKA pathway caused a total block of CREB phosphorylation and significantly reduced IFN(gamma), IL-2 and IL-2R(alpha) gene expression by approximately 40% (p<0.001). PKC(theta) plays a major role in T-cell activation: inhibition of PKC significantly reduced the expression of IFN(gamma), IL-2 and IL-2R(alpha). Since PKC blocked activation of CREB, we studied potential cross-talk between the PKC and the PKA/MAPK pathways, PMA-stimulated Jurkat cells were studied with specific signal pathway inhibitors. Extracellular signal-regulated kinase-2 (ERK2) pathway was found to be significantly activated greater than seven-fold within 30 min; however, there was little activation of ERK-1 and no activation of JNK or p38 MAPK. Inhibition of the PKA pathway, but not the PKC pathway, resulted in inhibition of ERK1/2 activation at all time points, inhibition of MEK1 and 2 significantly blocked expression of IL-2 and IL-2R(alpha). Gene expression of IL-2R(alpha) and IFN(gamma) was dependent on PKA in S49 wt cells but not in kin- mutants. Using gel shift analysis, we found that forskolin activation of T-cells resulted in activation of AP1 sites; this increase in nuclear extract AP1 was significantly blocked by MEK1 inhibitor U0126. Taken together, these results suggest that the PKA in addition to PKC and MAPK pathways plays a role in early T-cell activation and induction of IL-2, IL-2R(alpha) and IFN(gamma) gene expression.

Non-NASA Center↗
NASA NTRS2011

Magnetotail Reconnection and Flux Circulation: Jupiter and Saturn Compared

The Jovian magnetosphere has been visited by eight spacecraft, and the magnetometer data have been used to identify dozens of plasmoids and ~250 field dipolarizations associated with magnetic reconnection in the tail [e.g. Vogt et al., 2010]. Since the arrival of the Cassini spacecraft at Saturn in 2004, the magnetometer instrument has also been used to identify reconnection signatures. The deepest magnetotail orbits were in 2006, and during this time 34 signatures of plasmoids were identified. In this study we compare the statistical properties of plasmoids at Jupiter and Saturn such as duration, size, location, and recurrence period. Such parameters can be influenced by many factors, including the different Dungey cycle timescales and cross-magnetospheric potential drops at the two planets. We present superposed epoch analyses of plasmoids at the two planets to determine their average properties and to infer their role in the reconfiguration of the nightside of the magnetosphere. We examine the contributions of plasmoids to the magnetic flux transfer cycle at both planets. At Jupiter, there is evidence of an extended interval after reconnection where the field remains northward (analogous to the terrestrial post-plasmoid plasma sheet). At Saturn we see a similar feature, and calculate the amount of flux closed on average in reconnection events, leading us to an estimation of the recurrence rate of plasmoid release.

Jackman, C. M.↗
NASA NTRS2014

Overview of the Contributing Factor Map and How it can Support your Research

The Contributing Factor Map (CFM) is a visual representation of a taxonomy of factors influencing human health and performance in space. This presentation will give an overview of its development and its structure. It will describe various uses of the CFM that can support researchers working within the Human Research Program (HRP) Architecture of Evidence-Risk-Gap-Task-Deliverable. For example, during the Risk phase, the CFM can be used as a "menu" to help formulate a qualitative model of the factors contributing to specific consequences of concern. It provides a reference set of factors from across the operational, vehicle design, and human domains that otherwise might not be considered if approaching a risk from a specific domain perspective. Using the CFM as a reference can increase awareness of potential cross-disciplinary collaborations for overall risk mitigation. The CFM can also be used as a framework for identifying gaps in knowledge about a risk. This identification can support the subsequent development of gaps and tasks comprising the research plan aimed at risk mitigation. Examples of these types of applications of the CFM will be discussed and information on the support available to researchers in using it will be provided.

Mindock, Jennifer A.↗