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Recurrent cosmic-ray modulation phenomena with Forbush decrease characteristics correlated with M-region magnetic storms, concluding that each series results from shock wave solar initiated
The engineered macro-pore foam provides a new way to study thermonuclear burn physics by utilizing capsules containing deuterated (D) foam and filling tritium (T) gas in the engineered macro-pores. The implosion of a thermonuclear capsule filled with an engineered macro-pore foam will be complex due to the interaction of a shock wave with the engineered macro-pores. It is our goal to quantify how substantially complex foam structures affect the shape of shock and bulk shock speed. A cylinder-shape shock tube experiment has been designed and performed at the Omega Laser Facility. In order to examine how a foam structure will affect shock propagation, we performed several tests varying (1) engineered macro-pore size, (2) average foam density, and (3) with/without neopentane (C 5 H 12 ) gas. X-ray radiographic data indicate that shock speed through engineered macro-pore foams depends strongly on average foam density and less on pore size. In this work, experimental shock propagation data helped guide two numerical simulation approaches: (1) a 2D simulation with homogenizing foams rather than explicitly simulating engineered macro-pores and (2) a 2D toroidal-pore approximation adopting a toroidal-tube geometry to model engineered macro-pores.
Understanding longer timescale material reactions under dynamic stress loading is critical for applications in materials engineering, shock physics, and planetary science. Prompt impulse experiments generate lower pressures since the ablator—the material first removed by the laser—is thicker and farther from the diagnostic plane, capturing aggregate material responses from the initial shock wave, rarefaction waves, and later time effects. This complexity demands thorough material characterization and simulation support. Since traditional sample construction is specific to supported shock experiments, designing prompt impulse experiments requires reconsideration around target design and sample engineering. Here, we present sample preparation techniques, experimental investigations, and theoretical simulations to investigate glue layer impacts, aiming to standardize samples for consistent data at lower laser fluences. We find that glue layers <30 μm have a minimal impact on peak velocity and pulse shape. The peak velocity scales linearly with glue layer thickness until a glue layer of 75 μm. For glue layers >75 μm, the peak velocity no longer scales with thickness; however, the pulse shape continues to degrade as described by simulations.
Contents include the following: Ca-, Al-Rich Inclusions and Ameoboid Olivine Aggregates: What We Know and Don t Know About Their Origin. Aluminium-26 and Oxygen Isotopic Distributions of Ca-Al-rich Inclusions from Acfer 214 CH Chondrite. The Trapping Efficiency of Helium in Fullerene and Its Implicatiion to the Planetary Science. Constraints on the Origin of Chondritic Components from Oxygen Isotopic Compositions. Role of Planetary Impacts in Thermal Processing of Chondrite Materials. Formation of the Melilite Mantle of the Type B1 CAIs: Flash Heating or Transport? The Iodine-Xenon System in Outer and Inner Portions of Chondrules from the Unnamed Antarctic LL3 Chondrite. Nucleosynthesis of Short-lived Radioactivities in Massive Stars. The Two-Fluid Analysis of the Kelvin-Helmholtz Instability in the Dust Layer of a Protoplanetary Disk: A Possible Path to the Planetesimal Formation Through the Gravitational Instability. Shock-Wave Heating Model for Chonodrule Formation: Heating Rate and Cooling Rate Constraints. Glycine Amide Hydrolysis with Water and OH Radical: A Comparative DFT Study. Micron-sized Sample Preparation for AFM and SEM. AFM, FE-SEM and Optical Imaging of a Shocked L/LL Chondrite: Implications for Martensite Formation and Wave Propagation. Infrared Spectroscopy of Chondrites and Their Components: A Link Between Meteoritics and Astronomy? Mid-Infrared Spectroscopy of CAI and Their Mineral Components. The Origin of Iron Isotope Fractionation in Chondrules, CAIs and Matrix from Allende (CV3) and Chainpur (LL3) Chondrites. Protoplanetary Disk Evolution: Early Results from Spitzer. Kinetics of Evaporation-Condensation in a Melt-Solid System and Its Role on the Chemical Composition and Evolution of Chondrules. Oxygen Isotope Exchange Recorded Within Anorthite Single Crystal in Vigarano CAI: Evidence for Remelting by High Temperature Process in the Solar Nebula. Chondrule Forming Shock Waves in Solar Nebula by X-Ray Flares. Organic Globules with Anormalous Nitrogen Isotopic Compositions in the Tagish Lake Meteorite: Products of Primitive Organic Reactions. Yet Another Chondrule Formation Scenario. CAIs are Not Supernova Condensates. Microcrystals and Amorphous Material in Comets and Primitive Meteorites: Keys to Understanding Processes in the Early Solar System. A Nearby Supernova Injected Short-lived Radionuclides into Our Protoplanetary Disk. REE+Y Systematics in CC and UOC Chondrules. Meteoritic Constraints on Temperatures, Pressures, Cooling Rates, Chemical Compositions, and Modes of Condensation in the Solar Nebula. The I-Xe Record of Long Equilibration in Chondrules from the Unnamed Antarctic Meteorite L3/LL3. Early Stellar Evolution.
Approximative solutions for diffracted and focusing wave front expansions in sonic boom shock wave propagation
First experimental line strength data for the visible Kr II lines and for several of the more prominent Kr I lines are given. The spectroscopic light source used is the thermal plasma behind the reflected shock wave in a gas-driven shock tube. A 3/4-m spectrograph and a 1-m spectrograph were employed simultaneously to provide redundant photometry. The data are compared with other measurements and with theoretical calculations.
Some current problems in noise pollution which involve the dynamics of weak shock waves can be succesfully investigated using shock tubes and shock-tube techniques. Two examples presently under study are discussed; in one case the experiments are carried out in a large, conventional shock tube originally designed for studies of rarefied gasdynamics, while in the other case the experimental facility is a less conventional 'repeating' shock tube.
Electron density, electron temperature, and concentration of excited sodium atoms are measured in the weakly ionized regime behind a shock wave in impure argon in a shock tube using microwave techniques and spectrally resolved radiometry. Evidence is presented to show that an apparent increase in the rate of ionization is due to electron detachment of negative chlorine ions produced from sodium chloride vapor contained as an impurity. To be consistent with this chemical model, rate coefficients are found in the temperature range between 5500 and 8600 K for the dissociation of NaCl into an ion pair, dissociation of NaCl into a neutral pair, and electron detachment of a negative chlorine ion. Electron temperature is lower than heavy-particle temperature by roughly 1000 K. The electron-argon impact-ionization rate coefficient is a weak function of electron temperature in contradiction to expectation.
Absolute transition-probability parameters are reported for seven band systems of the C2 molecule. These include all the known C2 band systems in the spectral region between 0.2 and 1.2 microns with the exception of the Messerle-Krauss system. To obtain the data, absolute intensities of selected spectral regions were measured behind the incident shock wave in a combustion-driven shock tube containing 85% Ar and 15% C2H2. These measurements were converted into electronic transition moments by a synthetic spectrum analysis. The electronic transition moments were then used to determine extensive tables of the transition-probability parameters for each of the band systems measured.
Liquid and solid rocket motor propulsion systems create an overpressure wave during ignition, caused by the accelerating gas particles pushing against or displacing the air contained in the launch pad or launch facility and by the afterburning of the fuel-rich gases. This wave behaves as a blast or shock wave characterized by a positive triangular-shaped first pulse and a negative half-sine wave second pulse. The pulse travels up the space vehicle and has the potential of either overloading individual elements or exciting overall vehicle dynamics. The latter effect results from the phasing difference of the wave from one side of the vehicle to the other. This overpressure phasing, or delta P environment, because of its frequency content as well as amplitude, becomes a design driver for certain panels (e.g., thermal shields) and payloads for the Space Shuttle. The history of overpressure effects on the Space Shuttle, the basic overpressure phenomenon, Space Shuttle overpressure environment, scale model overpressure testing, and techniques for suppressing the overpressure environments are considered.
Recent results concerning numerical simulation of shock waves using spectral methods are reviewed. Shock fitting techniques were discussed as well as shock capturing techniques with finite difference artificial viscosity. Also the notion of the information contained in the numerical results obtained by spectral methods and show how this information is recovered was discussed.
For this review, a selection has been made of a number of topics which are current active areas of both observational and theoretical research. Observations of Type III bursts are examined, taking into account ground-based observations (above approximately 8 MHz), spacecraft observations (below 1 MHz), and Langmuir waves and electron streams. Microwave bursts are considered along with Type II bursts, moving Type IV bursts, and Type I noise storms. The theory of Type III radio bursts (radio emission from electron streams) is discussed, giving attention to quasi-linear theory, induced scatter of ions, wave-wave effects of the nonlinear refractive and self-focusing variety, the second harmonic emission from Langmuir waves, fundamental emission from Langmuir waves, and density irregularities and ion-acoustic waves. Aspects of radio emission from shock waves and current sheets are also studied.
An investigation was conducted in a 3.4- by 3.4-inch duct to determine the characteristics of the supersonic flow downstream of four wire-mesh screen nozzles with nominal design Mach numbers in the range between 1.97 and 2.58. Two types of disturbances were observed in the flow field: a fine network of interacting expansion and compression waves which were formed immediately downstream of the screens and appeared to dissipate within 25 to 40 wave intersections; and relatively strong oblique shock waves that originated at the junctions of the screens and the walls and were reflected throughout the length of the duct. Regions of fairly uniform flow were found to exist. The total-pressure loss across the screens varied from 22 percent at Mach number 1.58 to 43 percent at Mach number 2.06.
The impact of an isolated vortex in a compressible Keplerian disk is examined using higher order numerical solutions of the Euler and entropy-conserving Energy equations. The vortex is stretched by the background shear flow with longer lasting anticyclonic vortices persisting for about 10 vortex revolutions. Simultaneously, the vortex emits transient radial waves consisting mainly of axisymmetrical weak shock waves and a slower, nonaxisymmetric Rossby wave. These waves may contribute to certain transient events in protoplanetary disks. The vortex stretching and waves were found to have little long-term feedback on the baseline 'standard solar nebula' disk structure and confirm the extremely stable structure of non self-gravitating disks.
The goal of the Living With a Star program is to understand the Sun-Earth connection sufficiently well that we can solve problems critical to life and society. This can most effectively be done in the short term using observations from our past and on-going programs. Not only can this approach solve some of the pressing issues but also it can provide ideas for the deployment of future spacecraft in the LWS program. The proposed effort uses data from NEAR, SOHO, Wind, ACE and Pioneer Venus in quadrature, multipoint, and solar cycle studies to study the interplanetary coronal mass ejection and its role in the magnetic flux cycle of the Sun. ICMEs are most important to the LWS objectives because the solar wind conditions associated with these structures are the most geoeffective of any solar wind phenomena. Their ability to produce strong geomagnetic disturbances arises first because of their high speed. This high speed overtakes the ambient solar wind producing a bow shock wave similar to the terrestrial bow shock. In the new techniques we develop as part of this effort we exploit this feature of ICMEs. This shocked plasma has a greater velocity, higher density and stronger magnetic field than the ambient solar wind, conditions that can enhance geomagnetic activity. The driving ICME is a large magnetic structure expanding outward in the solar wind [Gosling, 19961. The ICMEs magnetic field is generally much higher than that in the ambient solar wind and the velocity is high. The twisted nature of the magnetic field in an ICME almost ensures that sometime during the ICME conditions favorable for geomagnetic storm initiation will occur.
Rate coefficients of the title reaction R(sub 31) (SO2 +O+M yields SO3 +M) and R(sub 56) (SO2 + HO2 yields SO3 +OH), important in the conversion of S(IV) to S(VI),were obtained at T =970-1150 K and rho (sub ave) = 16.2 micro mol/cubic cm behind reflected shock waves by a perturbation method. Shock-heated H2/ O2/Ar mixtures were perturbed by adding small amounts of SO2 (1%, 2%, and 3%) and the OH temporal profiles were then measured using laser absorption spectroscopy. Reaction rate coefficients were elucidated by matching the characteristic reaction times acquired from the individual experimental absorption profiles via simultaneous optimization of k(sub 31) and k(sub 56) values in the reaction modeling (for satisfactory matches to the observed characteristic times, it was necessary to take into account R(sub 56)). In the experimental conditions of this study, R(sub 31) is in the low-pressure limit. The rate coefficient expressions fitted using the combined data of this study and the previous experimental results are k(sub 31,0)/[Ar] = 2.9 10(exp 35) T(exp ?6.0) exp(?4780 K/T ) + 6.1 10(exp 24) T(exp ?3.0) exp(?1980 K/T ) cm(sup 6) mol(exp ?2)/ s at T = 300-2500 K; k(sub 56) = 1.36 10(exp 11) exp(?3420 K/T ) cm(exp 3)/mol/s at T = 970-1150 K. Computer simulations of typical aircraft engine environments, using the reaction mechanism with the above k(sub 31,0) and k(sub 56) expressions, gave the maximum S(IV) to S(VI) conversion yield of ca. 3.5% and 2.5% for the constant density and constant pressure flow condition, respectively. Moreover, maximum conversions occur at rather higher temperatures (?1200 K) than that where the maximum k(sub 31,0) value is located (approximately 800 K). This is because the conversion yield is dependent upon not only the k(sup 31,0) and k(sup 56) values (production flux) but also the availability of H, O, and HO2 in the system (consumption flux).
Interplanetary Monitoring Platform magnetic field experiment - interpretation of data on magnetospheric boundary and collisionless magnetohydrodynamic shock waves
Numerical solution of Bhatnagar-Gross-Krook model for shock wave structure problem, noting Chapman-Enskog approximation