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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 OSTI2025

Hydrodynamic expansion and near-infrared absorption of x-ray heated aluminum plasmas

We use x-ray pulses from dense argon plasmas at the Z Machine (Sandia National Laboratories) to generate hypersonic aluminum plasmas akin to material ejecta during proposed planetary defense missions, fusion reactor wall excursions, and other high-energy density processes. Near-infrared absorption is used to diagnose the controlled expansion of the plasmas through cylindrical cavities following their generation from x-ray heating of solid aluminum 7075 alloy. The data are compared to multidimensional radiation hydrodynamics simulations utilizing the ALEGRA multiphysics code, accounting for the dynamics of radiation scattering, material phase change, plasma expansion, thermal re-irradiation, and interactions with the cavity and with the infrared beams. To allow for accurate simulation, density functional theory is used to apply the Hagen–Rubens relation for the far-infrared and is adjoined with a detailed configuration accounting model using the Propaceos code, producing opacities spanning 10 −1 –10 4 eV photon energy for aluminum 7075 alloy, and in comparison with pure aluminum. The model is found to agree with experimental data in the higher-fluence regime when the Hagen–Rubens relation is applied. The ejected material, which is observed to travel up to 55 km/s, is comprised of a strongly ionized, non-LTE plasma front at ∼10 eV temperature followed by a weakly ionized LTE gas at higher density. The present findings lend some confidence to the broad-range equation of state and infrared opacity models for weakly ionized aluminum plasmas while demonstrating an approach to their future refinement, with potential application to astrophysical plasmas and other extreme processes.

Adiabatic process↗
DOE OSTI2025

Thermodynamic properties of “near-perfect” gas

When applied thermodynamics requires simple representations of thermodynamic quantities, one often finds quantities such as pressure and the thermal energy density expressed as a monomial linear product of density and temperature power laws. This is a simple generalization of the product of density and temperature used for the perfect gas that admits a broader range of thermodynamic behavior into analytic fluid calculations or provides an analytic form that is readily fit to tabulated equation-of-state data for an arbitrary material. This paper reviews the thermodynamic properties of this generalized perfect-gas model, treating it as a class of “near-perfect-gas” models that are defined and unified here, for the first time, through a shared Helmholtz free energy. This generalization from perfect to near-perfect-gas models preserves some perfect-gas properties (e.g., constant adiabatic exponents) but not others (e.g., constant specific heats) and is constrained by thermodynamic consistency. It is important to be aware of the properties of this class of near-perfect-gas models when using them as surrogates for real nonperfect materials that may have properties that cannot be captured by near-perfect-gas models.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1984

Normal Mode Initialization

The objective of this research is the development and implementation of normal mode procedures for use with the GLAS analysis/forecast system. Specific tasks of this work include: (1) high latitude filtering of model fields to preserve the GLAS GCM's linear stability during integration; (2) development of nonlinear normal mode initialization (NLNMI) processes, both adiabatic and diabatic. Using NLNMI to initialize GLAS analyses; investigation of the impact of normal mode initialization on the GLAS analysis/forecast system, especially in regard to data assimilation; and (3) diagnosis of the 1-3 day systemic forecast errors of the GLAS GCM.

Bloom, S. C.↗
NASA NTRS1986

Modulation of galactic cosmic rays in the heliosphere

Observations of the intensity of galactic cosmic rays and anomalous components near earth and in the outer heliosphere are providing important tests for theories of solar modulation. The most recent observations show effects that seem to require that models for modulation include gradient and curvature drifts as well as the conventional processes of convection, adiabatic deceleration, and diffusion. New observations are required to define the interplay of these processes in the three-dimensional heliosphere.

Mckibben, R. B.↗
NASA NTRS1976

Retrodictive determinism

With respect to irreversible, non-homeomorphic maps, contravariant and covariant tensor fields have distinctly natural covariance and transformational behavior. For thermodynamic processes which are non-adiabatic, the fact that the process cannot be represented by a homeomorphic map emphasizes the logical arrow of time, an idea which encompasses a principle of retrodictive determinism for covariant tensor fields.

Kiehn, R. M.↗
NASA NTRS1989

The role of diabatic heating in maintaining the upper-tropospheric baroclinic zone in the South Pacific

The four-dimensional structure of the region in the South Pacific convergence zone (SPCZ) during January 10-18, 1979 is studied using a modified set of ECMWF FGGE level III-b analyses. The effects of kinematic and thermodynamic processes on maintaining the upper baroclinic region corresponding with the subtropical jet are analyzed. The role of adiabatic and diabatic processes in the maintenance of baroclinicity in the area of the SPCZ is examined using the frontogenetical function. It is observed that the processes affecting the evolution of baroclinicity in the SPCZ region differ from those in the middle latitude; possible reasons for these differences are proposed.

Robertson, Franklin R.↗
NASA NTRS1987

Numerical simulations of the subsynoptic features associated with the AVE-SESAME I case. I - The preconvective environment

The extensive diagnostic calculations made possible by the AVE-SESAME I database are used in combination with numerical simulations from the Mesoscale Atmospheric Simulation System (MASS) model to examine the dynamics of the meso-alpha-scale features during the preconvective period from 1130 to 2030 UTC on April 10, 1979. The version of the MASS model used in this investigation is presented, and an overview of the general synoptic conditions present at the time of model initialization is presented along with the data used to initialize the model. The dynamical processes present in the numerical simulations are presented and compared with analyses of the observational data from this and other investigations of this case. The relative importance of the adiabatic and diabatic processes in creating and then initiating the release of the convective instability is discussed.

Zack, John W.↗
NASA NTRS1986

Effects of three-dimensional heliospheric structures on cosmic-ray modulation

The theory of cosmic-ray transport in the heliosphere contains four distinct physical processes - diffusion, convection, adiabatic cooling, and drifts. The last of these has only recently been evaluated. Extrapolation of present understanding of the regions near the heliospheric equator to high heliographic latitudes leads to the conclusion that particle drift in the large-scale magnetic field plays an important role in cosmic-ray modulation. The large-scale, three-dimensional structure of the interplanetary magnetic field is therefore very important in understanding cosmic rays. Several key observed modulation effects are summarized, each of which is a natural consequence of drift, but which requires special assumptions if drift plays no role. It is concluded that particle drifts play an important and possibly dominant role in transport in the heliosphere.

Jokipii, J. R.↗
NASA NTRS1985

Diagnostics of severe convection and subsynoptic scale ageostrophic circulations

Diagnostics of severe convection and subsynoptic scale ageostrophic circulations are reported. Mesoscale circulations through forcing of ageostrophic motion by adiabatic, diabatic and frictional processes were studied. The development and application of a hybrid isentropic sigma coordinate numerical model was examined. The numerical model simulates mesoscale ageostrophic circulations associated with propagating jet streaks and severe convection. A complete list of publications and these completed through support of the NASA severe storms research project is included.

Source record↗
NASA NTRS1989

ISEE 3 observations of solar wind thermal electrons with T-perpendicular greater than T-parallel

This study presents ISEE 3 observations of anomalous electron distributions for which T-perpendicular exceeds T-parallel in the solar wind near 1 AU. Twelve anomaly events were identified, lasting from 24 min to 6 hours. These events generally share the following characteristics: (1) high plasma density, (2) low solar wind speed, (3) magnetic field which is nearly transverse to the flow, and (4) low electron and ion temperatures. The processes of solar wind adiabatic expansion and isotropization via Coulomb collisions could be expected to lead to such anomalous anisotropies under conditions similar to those observed. However, these conditions actually produce T-perpendicular greater than T-parallel for only a small fraction of the time, suggesting that other mechanisms are also important in regulating solar wind electron distributions.

Phillips, J. L.↗
NASA NTRS1987

Evolution of interstellar pickup ions in the solar wind

A model is constructed for the evolution of an interstellar pickup ion distribution in the solar wind. The model assumes that the ions are immediately isotropized at ionization and follows the subsequent development of the distribution function as the particles are convected with the solar wind. The effects of energy diffusion in an ambient wave field with a power law spectrum, adiabatic deceleration in the expanding solar wind, and continual addition of newly ionized particles are all included in the model. An analytical expression describing the evolution of the distribution function in phase space velocity and heliocentric radius is obtained. The distribution quickly approaches an asymptotic shape in phase space which depends on the relative efficiency of the energy diffusion process compared to that of adiabatic deceleration. At large distances from the sun the density of pickup ions falls as 1/r in this model. An expression for the distribution function at large distances and for large particle speed is presented. The asymptotic shape should describe the distribution of pickup ions in the outer heliosphere and could be used as an input distribution for a model of the anomalous component of heliosphere and could be used as an input distribution for a model of the anomalous component of cosmic rays. Comparison of this work with the recent observation of He(+) at 1 AU implies that the energy diffusion process is very weak inside 1 AU.

Isenberg, Philip A.↗
NASA NTRS1976

Planetary spin period acceleration of particles in the Jovian magnetosphere

A four-step mechanism is proposed for the acceleration of energetic protons and relativistic electrons in Jupiter's magnetosphere. According to this mechanism, photoelectrons and ions from the Jovian ionosphere are: (1) ejected along magnetic-field lines toward the equator by the centrifugal force of corotation; (2) accelerated by magnetic-field annihiliation in the magnetotail, which process is modulated at Jupiter's rotational frequency; (3) trapped on closed field lines in the reconnection process, convected inward toward Jupiter from the merging region, and subjected to adiabatic compression; and (4) diffused inward by the conventional radial-diffusion process through a violation of the third adiabatic invariant. It is shown that the proposed mechanism produces magnetic moments much larger than those available from inward diffusion of solar-wind particles or motional emf acceleration at the Galilean satellites, provides a natural explanation for the 10-hr periodicity of the energetic particle fluxes observed inside the magnetosphere by the Pioneer spacecraft, and also produces a 10-hr periodicity in the energetic particle flux from the magnetosphere into interplanetary space in such a way that the phase of interplanetary flux variations is locked to the rotational phase of Jupiter

Carbary, J. F.↗
DOE OSTI2025

Stability of superconducting strings

We investigate the stability of superconducting strings as bound states of strings and fermion zero modes at both the classical and quantum levels. The dynamics of these superconducting strings can result in a stable configuration, known as a vorton . We mainly focus on global strings, but the majority of the discussion can be applied to local strings. Using lattice simulations, we study the classical dynamics of superconducting strings and confirm that they relax to the vorton configuration through Nambu-Goldstone boson radiation, with no evidence of over-shooting that would destabilize the vorton. We explore the tunneling of fermion zero modes out of the strings. Both our classical analysis and quantum calculations yield consistent results: the maximum energy of the zero mode significantly exceeds the fermion mass, in contrast to previous literature. Additionally, we introduce a world-sheet formalism to evaluate the decay rate of zero modes into other particles, which constitute the dominant decay channel. We also identify additional processes that trigger zero-mode decay due to non-adiabatic changes of the string configuration. In these decay processes, the rates are suppressed by the curvature of string loops, with exponential suppression for large masses of the final states. We further study the scattering with light charged particles surrounding the string core produced by the zero-mode current and find that a wide zero-mode wavefunction can enhance vorton stability.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1971

The propagation of solar cosmic-ray bursts.

Description of a model showing analytically the three phases of anisotropy which occur during solar cosmic-ray events in the 7.5 to 21 MeV kinetic-energy interval and reported by McCracken et al. (1971): (1) a highly anisotropic, near field-aligned, initial phase, (2) a convective phase, and (3) a late-time phase in which the anisotropy is approximately perpendicular to the mean interplanetary magnetic field. The model is based on the cosmic-ray particles being convectively transported out from the sun, undergoing anisotropic diffusion along the interplanetary magnetic-field lines, and losing energy by adiabatic deceleration or by collision processes. The event is seen simply as a pulse moving outward from the sun after a cosmic-ray burst with a negative density-gradient in front of it and a positive gradient behind.

Ng, C. K.↗
DOE OSTI2025

Adiabatic cooling of planar motion in a Penning-trap ion crystal to sub-millikelvin temperatures

Two-dimensional planar ion crystals in a Penning trap are a platform for quantum information science experiments. However, the low-frequency planar modes of these crystals are not efficiently cooled by laser cooling, which can limit the utility of the drumhead modes for quantum information processing. Recently, it has been shown that nonlinear mode coupling can enhance the cooling of the low-frequency planar modes. Here, in this study, we demonstrate in numerical simulations that this coupling can be dynamically tuned by adiabatically changing the rotation frequency of the ion crystal during experiments. Furthermore, we show that this technique can, in addition, produce lower temperatures for the low-frequency planar modes via an adiabatic cooling process. This result allows cooling of the planar modes to sub-millikelvin temperatures, resulting in improved spectral resolution of the drumhead modes at experimentally relevant rotation frequencies, which is crucial for quantum information processing applications.

Johnson, Wes [Univ. of Colorado, Boulder, CO (Unit↗
DOE OSTI2025

Quantum heat engine based on quantum interferometry: The SU(1,1) Otto cycle

We present a quantum heat engine based on a quantum Otto cycle whose working substance reproduces the same outcomes as an SU ( 1 , 1 ) interference process at the end of each adiabatic transformation. This device takes advantage of the extraordinary quantum metrological features of the SU ( 1 , 1 ) interferometer to better discriminate the sources of uncertainty of relevant observables during each adiabatic stroke of the cycle. In particular, the SU ( 1 , 1 ) adiabatic transformations enable high-precision estimations of the energy extracted from the adiabatic stroke, despite the presence of thermal fluctuations. Applications to circuit QED platforms are also discussed. Published by the American Physical Society 2025

Ferreri, Alessandro (ORCID:0000000185459205)↗
NASA NTRS1973

Diffusion of ring current particles by low-frequency long-wavelength electrostatic oscillations.

The diffusion of charged particles by randomly fluctuating low-frequency long-wavelength electrostatic oscillations in the magnetosphere is investigated as a possible mechanism for transporting ring current particles. The diffusion process is assumed to preserve the first adiabatic invariant. The magnetosphere is represented by a simple model with cylindrical geometry. In the model the ionospheres are assumed to be perfectly conducting and the ring current is assumed to have a Maxwellian distribution of velocities. The electrostatic oscillations are treated as natural modes of the magnetospheric cavity which are driven by variations in the electric potential on the magnetopause. It is concluded that diffusion of ring current protons by this process is not important in the magnetosphere.

Maggs, J. E.↗