Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Interaction Region”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

High Temperature Fuel Cladding Chemical Interactions Between Unirradiated TRIGA Fuels and 304 Stainless Steel

High temperature fuel cladding chemical interactions (FCCI) between Training-Research, Isotopes-General-Atomics (TRIGA) fuel elements and their 304 stainless steel (304SS) cladding are of interest to develop an understanding of the fuel-behavior during transient reactor scenarios. TRIGA fuels are composed of uranium particles dispersed in a zirconium hydride (Zr H) matrix encased in a 304SS cladding. At high temperatures, the fuel and cladding have the potential experience FCCI. A large number of interactions can take place in this multi-component fuel system. Emphasis is given to the development of low melting point phases. Diffusion couples of TRIGA fuel vs. 304SS were annealed at 1000°C for 5 and 24 hours. Characterization was then carried out via scanning electron microscopy and transmission electron microscopy. The as-received and annealed microstructures of the fuel and the interactions regions between the fuel and the 304SS will be discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Long-term Longitudinal Recurrences of the Open Magnetic Flux Density in the Heliosphere

Open magnetic flux in the heliosphere is determined from the radial component of the magnetic field vector measured onboard interplanetary space probes. Previous Ulysses research has shown remarkable independence of the flux density from heliographic latitude, explained by super-radial expansion of plasma. Here we are investigating whether any longitudinal variation exists in the 50 year long OMNI magnetic data set. The heliographic longitude of origin of the plasma package was determined by applying a correction according to the solar wind travel time. Significant recurrent enhancements of the magnetic flux density were observed throughout solar cycle 23, lasting for several years. Similar, long-lasting recurring features were observed in the solar wind velocity, temperature and the deviation angle of the solar wind velocity vector from the radial direction. Each of the recurrent features has a recurrence period slightly differing from the Carrington rotation rate, although they show a common trend in time. Examining the coronal temperature data of ACE leads to the possible explanation that these long-term structures are caused by slow–fast solar wind interaction regions. A comparison with MESSENGER data measured at 0.5 au shows that these longitudinal magnetic modulations do not exist closer to the Sun, but are the result of propagation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

PRESSURE PULSES AT VOYAGER 2 : DRIVERS OF INTERSTELLAR TRANSIENTS?

Voyager 1 ( V1 ) crossed the heliopause into the local interstellar medium (LISM) in 2012. The LISM is a dynamic region periodically disturbed by solar transients with outward-propagating shocks, cosmic-ray intensity changes and anisotropies, and plasma wave oscillations. Voyager 2 ( V2 ) trails V1 and thus may observe the solar transients that are later observed at V1. V2 crossed the termination shock in 2007 and is now in the heliosheath. Starting in 2012, when solar maximum conditions reached V2 , five possible merged interaction regions (MIRs) have been observed by V2 in the heliosheath. The timing is consistent with these MIRs driving the transients observed by V1 in the LISM. The largest heliosheath MIR was observed by V2 in late 2015 and should reach V1 in 2018.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

The Ghost Collider: An Innovative Higgs Factory

The Ghost Collider is an innovative proposal for a 550 GeV centre-of-mass, 275 GeV per beam linear collid-er with four interaction regions, each with the design luminosity. The primary innovation is the use of “ghost bunches” containing equal numbers of electrons and posi-trons so they are electrically neutral. In the linacs, energy is transferred between electrons and positrons in the same bunch, decelerating one type of particle and using the energy to accelerate the other: a new class of Energy Re-covery Linacs. At the interaction points, collisions be-tween two neutral ghost bunches occurs with weakened electromagnetic interaction such as the beam-beam effect or disruption, ensuring that the particles and their energy can be recycled with minimal loss. Four “serial IPs” are incorporated, where chromatic errors produced in one IP are cancelled in the following IP. The neutral beam insta-bility at the IP is also addressed. All interaction points have the nominal luminosity per IP of 2.8 x 1034 cm-2s-1 for a facility luminosity of 1.1 x1035 cm-2s-1 @ 100 MW electrical power for the RF systems. The result is a totally original concept for an electron-positron collider.

Hutton, A. [Thomas Jefferson National Accelerator ↗
NASA NTRS2012

Three-Dimensional Magnetohydrodynamic Modeling of the Solar Wind Including Pickup Protons and Turbulence Transport

To study the effects of interstellar pickup protons and turbulence on the structure and dynamics of the solar wind, we have developed a fully three-dimensional magnetohydrodynamic solar wind model that treats interstellar pickup protons as a separate fluid and incorporates the transport of turbulence and turbulent heating. The governing system of equations combines the mean-field equations for the solar wind plasma, magnetic field, and pickup protons and the turbulence transport equations for the turbulent energy, normalized cross-helicity, and correlation length. The model equations account for photoionization of interstellar hydrogen atoms and their charge exchange with solar wind protons, energy transfer from pickup protons to solar wind protons, and plasma heating by turbulent dissipation. Separate mass and energy equations are used for the solar wind and pickup protons, though a single momentum equation is employed under the assumption that the pickup protons are comoving with the solar wind protons.We compute the global structure of the solar wind plasma, magnetic field, and turbulence in the region from 0.3 to 100 AU for a source magnetic dipole on the Sun tilted by 0 deg - .90 deg and compare our results with Voyager 2 observations. The results computed with and without pickup protons are superposed to evaluate quantitatively the deceleration and heating effects of pickup protons, the overall compression of the magnetic field in the outer heliosphere caused by deceleration, and the weakening of corotating interaction regions by the thermal pressure of pickup protons.

Usmanov, Arcadi V.↗
NASA NTRS1985

Recent developments in the theory of AM Her and DQ Her stars

Recent advances in the theory of accreting magnetic white dwarf stars are described and several of the unresolved issues concerning them are discussed. Recently reported Einstein satellite observations are examined and the possibility is considered that the 'soft X-ray puzzle' in the AM Her stars may have disappeared. Based on these observations, the evidence is considered that the region emitting the polarized optical light is separate from the X-ray emission region. Among the theoretical advances described are extensive new calculations of the X-ray emission from accreting magnetic white dwarfs, including soft and hard X-ray pulse profiles and time-dependent behavior; improvements in the treatment of cyclotron emission and the transfer of radiation in magnetoactive plasmas, with application to the polarized optical light from the AM Her stars; new ideas about the stream-magnetosphere interaction region that produces the forest of strong emission lines in the AM Her stars; explanation of the synchronization of the white dwarf in the AM Her stars in terms of an MHD torque; and determination of the magnetic fields in the AM Her and DQ Her stars through analysis of their spin-up behavior.

Lamb, D. Q.↗
NASA NTRS2006

The Latitudinal Excursion of Coronal Magnetic Field Lines in Response to Differential Rotation: MHD Simulations

Solar energetic particles, which are believed to originate from corotating interacting regions (CIRS) at low heliographic latitude, were observed by the Ulysses spacecraft even as it passed over the Sun's poles. One interpretation of this result is that high-latitude field lines intercepted by Ulysses connect to low-latitude CIRs at much larger heliocentric distances. The Fisk model explains the latitudinal excursion of magnetic field lines in the solar corona and heliosphere as the inevitable consequence of the interaction of a tilted dipole in a differentially rotating photosphere with rigidly rotating coronal holes. We use a time-dependent three-dimensional magnetohydrodynamic (MHD) algorithm to follow the evolution of a simple model of the solar corona in response to the differential rotation of the photospheric magnetic flux. We examine the changes of the coronal-hole boundaries, the redistribution of the line-of-sight magnetic field, and the precession of field lines in the corona. Our results confirm the basic idea of the Fisk model, that differential rotation leads to changes in the heliographic latitude of magnetic field lines. However, the latitudinal excursion of magnetic field lines in this simple "tilted dipole" model is too small to explain the Ulysses observations. Although coronal holes in our model rotate more rigidly than do photospheric features (in general agreement with observations), they do not rotate strictly rigidly as assumed by Fisk. This basic difference between our model and Fisk's will be explored in the future by considering more realistic magnetic flux distributions, as observed during Ulysses polar excursions.

Lionello, Roberto↗
NASA NTRS1983

The radial evolution of the solar wind, 1-10 AU

The interplanetary plasma and magnetic field observations from 1 to 10 AU are reviewed. Over this distance no clear reduction in average speed is seen. The range of wind speeds becomes smaller though high speed streams are still observed. The density, temperature and magnetic field profiles become dominated by the large values seen in the co-rotating interaction regions. The temperature falls more slowly than would be expected from a simple, adiabatic model. Co-rotating shocks appear beyond approximately 3 AU in Voyager data as opposed to beyond approximately 1.5 AU in the Pioneer data. Reverse shocks appear later than forward shocks; reverse shocks do not begin to appear until approximately 4 AU; reverse shocks appear to decay more rapidly than forward shocks. No clear effect due to interaction with the interstellar medium was seen in this radial range.

Gazis, P. R.↗
NASA NTRS1995

Energetic particles and coronal mass ejections in the high latitude heliosphere: Ulysses-LET observations

The COSPIN Low Energy Telescope (LET) onboard the Ulysses spacecraft measures protons, alphas and heavier ions at energies of approximately 1 to 50 MeV/n. Ulysses measurements offer favorable opportunities to study the effects of solar activity in the out-of-ecliptic regions of the heliosphere. Using LET data, we have investigated the properties of transient energetic ions at high heliographic latitudes when Ulysses was permanently immersed in high speed solar wind and magnetically connected to the Sun on open magnetic field lines. Recurrent increases in the fluxes of energetic ions at high heliographic latitudes at frequencies related to the solar rotation period were found to occur in association with co-rotating interaction regions (CIRs). Here we investigate fluxes of energetic particles that showed no relationship to ClRs. From the investigation of plasma and magnetic held data it is found that all of the transient high latitude particle events were associated with the passage of a coronal mass ejection (CME) over Ulysses. Enhancements in particle fluxes several days prior to the arrival of a CME, but with a significant time delay with respect to the estimated CME-onset at the Sun, were most probably associated with interplanetary shocks driven by fast CMEs. These particle events exhibit unusually high rho/alpha-ratios and are not observed for CMEs not driving a shock. However, not all CMEs that passed Ulysses were associated with a particle event. We find evidence that at high solar latitudes, solar flare particles cannot reach Ulysses on open magnetic field lines, but can reach the spacecraft if particles are injected into magnetic flux-ropes (CMEs) at the Sun. These findings are supported by soft X-ray observations from the Japanese Yohkoh-satellite.

Bothmer, V.↗
NASA NTRS2003

Dynamical Evolution of the Inner Heliosphere Approaching Solar Activity Maximum: Interpreting Ulysses Observations Using a Global MHD Model

In this study we describe a series of MHD simulations covering the time period from 12 January 1999 to 19 September 2001 (Carrington Rotation 1945 to 1980). This interval coincided with: (1) the Sun s approach toward solar maximum; and (2) Ulysses second descent to the southern polar regions, rapid latitude scan, and arrival into the northern polar regions. We focus on the evolution of several key parameters during this time, including the photospheric magnetic field, the computed coronal hole boundaries, the computed velocity profile near the Sun, and the plasma and magnetic field parameters at the location of Ulysses. The model results provide a global context for interpreting the often complex in situ measurements. We also present a heuristic explanation of stream dynamics to describe the morphology of interaction regions at solar maximum and contrast it with the picture that resulted from Ulysses first orbit, which occurred during more quiescent solar conditions. The simulation results described here are available at: http://sun.saic.com.

Riley, Pete↗
NASA NTRS1981

Prediction of subsonic aircraft flows with jet exhaust interactions

A numerical procedure to calculate the flow fields resulting from the viscous inviscid interactions that occur when a strong jet exhaust and aircraft flow field coupling exists was developed. The approach divides the interaction region into zones which are either predominantly viscous or inviscid. The flow in the inviscid zone, which surrounds most of the aircraft, is calculated using an existing potential flow code. The viscous flow zone, which encompasses the jet plume, is modeled using a parabolized Navier-Stokes code. The procedure features the coupling of the zonal solutions such that sufficient information is transferred between the zones to preserve the effects of the interactions. The zonal boundaries overlap and the boundary conditions are the information link between zones. An iteration scheme iterates the coupled analysis until convergence has been obtained.

Roberts, D. W.↗
DOE OSTI2021

Observations of pressure anisotropy effects within semi-collisional magnetized plasma bubbles

Magnetized plasma interactions are ubiquitous in astrophysical and laboratory plasmas. Various physical effects have been shown to be important within colliding plasma flows influenced by opposing magnetic fields, however, experimental verification of the mechanisms within the interaction region has remained elusive. Here we discuss a laser-plasma experiment whereby experimental results verify that Biermann battery generated magnetic fields are advected by Nernst flows and anisotropic pressure effects dominate these flows in a reconnection region. These fields are mapped using time-resolved proton probing in multiple directions. Various experimental, modelling and analytical techniques demonstrate the importance of anisotropic pressure in semi-collisional, high- β plasmas, causing a reduction in the magnitude of the reconnecting fields when compared to resistive processes. Anisotropic pressure dynamics are crucial in collisionless plasmas, but are often neglected in collisional plasmas. We show pressure anisotropy to be essential in maintaining the interaction layer, redistributing magnetic fields even for semi-collisional, high energy density physics (HEDP) regimes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Propagation effects in highly ionised gas media

The problem of propagation of an ultraintense pulse in a gas medium is solved by using a 3D nonadiabatic model extended to the case of multiple ionisation of atoms in the interaction region. A complex space – time coupling of the pulse during its propagation and strong spatial and temporal changes in the field distribution are shown. (extreme laser radiation: physics and fundamental applications)

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1976

Variations in plasma characteristics near D sheets in the solar wind

A strong interplanetary shock was detected by the Pioneer 8 magnetometer, plasma probe, and wave instrument at 0048 UT, on June 11, 1968. During the rest of this day the interplanetary medium was highly disturbed as seven well-defined current layers or D sheets, as well as a number of other localized interaction regions, swept past the spacecraft. The local plasma characteristics that were best correlated with passage of the D sheets appeared to involve changes in the suprathermal electron population. Changes in the 400-Hz wave levels were also detected near the discontinuities during periods when the local ion plasma frequency was near 400 Hz, but the limited measurement capability of the Pioneer 8 wave instrument does not allow an unambiguous identification of the wave-particle interactions associated with these measurements.

Scarf, F. L.↗
DOE OSTI2024

Evaluation of Sb-Nd and Te-Nd phases within the U-Zr fuel matrix and their interactions with HT9 alloy

Antimony (Sb) and tellurium (Te) were investigated as potential additives for U-10Zr (wt.%) metallic fuel to limit the fuel-cladding chemical interaction (FCCI) with HT-9 alloy. Neodymium (Nd) was utilized to simulate the formation of lanthanide-based solid fission products which are known to play a detrimental role in FCCI. Fuel alloys of U-Zr-Sb-Nd and U-Zr-Te-Nd were evaluated in their annealed condition and compared against their as-cast conditions. Isothermal diffusion couple experiments were performed between U-Zr-Nd, U-Zr-Sb-Nd, and U-Zr-Te-Nd against the cladding alloy HT9 to evaluate the effectiveness of the additives to stabilize Nd within the fuel alloys, as well as investigate the interaction regions that form between the different fuel alloys and HT9. Further, SbNd and Sb 3 Nd 4 , and TeNd are found to be the primary neodymium-based phases formed in the U-Zr-Sb-Nd and U-Zr-Te-Nd alloys, respectively. The zirconium-based phase, Zr 2 Sb, is also found to form within the former alloy. All phases were found to remain stable through the diffusion experiments and exhibited no interaction with HT9 constituent elements. Preferential interaction between Nd with additivities Te and Sb compared to constituting elements in HT9 was further verified based on density functional theory (DFT) calculated enthalpy of mixing.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

PROPAGATION OF THE 2012 MARCH CORONAL MASS EJECTIONS FROM THE SUN TO HELIOPAUSE

In 2012 March the Sun exhibited extraordinary activities. In particular, the active region NOAA AR 11429 emitted a series of large coronal mass ejections (CMEs) which were imaged by the Solar Terrestrial Relations Observatory as it rotated with the Sun from the east to west. These sustained eruptions are expected to generate a global shell of disturbed material sweeping through the heliosphere. A cluster of shocks and interplanetary CMEs were observed near the Earth, and are propagated outward from 1 AU using an MHD model. The transient streams interact with each other, which erases memory of the source and results in a large merged interaction region (MIR) with a preceding shock. The MHD model predicts that the shock and MIR would reach 120 AU around 2013 April 22, which agrees well with the period of radio emissions and the time of a transient disturbance in galactic cosmic rays detected by Voyager 1. These results are important for understanding the ''fate'' of CMEs in the outer heliosphere and provide confidence that the heliopause is located around 120 AU from the Sun.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Fermi bubbles inflated by winds launched from the hot accretion flow in Sgr A*

A pair of giant gamma-ray Bubbles has been revealed by Fermi-LAT. In this paper we investigate their formation mechanism. Observations have indicated that the activity of the supermassive black hole located at the Galactic center, Sgr A*, was much stronger than at the present time. Specifically, one possibility is that while Sgr A* was also in the hot accretion regime, the accretion rate should be 10{sup 3}-10{sup 4} times higher during the past ∼10{sup 7} yr. On the other hand, recent magnetohydrodynamic numerical simulations of hot accretion flows have unambiguously shown the existence and obtained the properties of strong winds. Based on this knowledge, by performing three-dimensional hydrodynamical simulations, we show in this paper that the Fermi Bubbles could be inflated by winds launched from the 'past' hot accretion flow in Sgr A*. In our model, the active phase of Sgr A* is required to last for about 10 million years and it was quenched no more than 0.2 million years ago. The central molecular zone (CMZ) is included and it collimates the wind orientation toward the Galactic poles. Viscosity suppresses the Rayleigh-Taylor and Kelvin-Helmholtz instabilities and results in the smoothness of the Bubbles edge. The main observational features of the Bubbles can be well explained. Specifically, the ROSAT X-ray features are interpreted by the shocked interstellar medium and the interaction region between the wind and CMZ gas. The thermal pressure and temperature obtained in our model are consistent with recent Suzaku observations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1982

Flow analysis of nozzle installations with strong airplane flow interactions

A numerical procedure has been developed to calculate the flow fields resulting from the viscous-inviscid interactions that occur when a strong jet exhaust and aircraft flow field coupling exists. The approach used in the current procedure is to divide the interaction region into zones which are either predominantly viscous or inviscid. The flow in the inviscid zone, which surrounds most of the aircraft, is calculated using an existing linearized potential flow code. The viscous flow zone, which encompasses the jet plume, is modeled using a parabolized Navier-Stokes code. The key feature of the present procedure is the coupling of the zonal solutions such that sufficient information is transferred between the zones to preserve the effects of the interactions. The zonal boundaries overlap with the boundary conditions being the information link between zones. An iteraction scheme iterates the coupled analysis until convergence has been obtained. The procedure has been successfully used for several test cases for which the computed results are presented.

Roberts, D. W.↗