Shock wave

About: Shock wave is a research topic. Over the lifetime, 36184 publications have been published within this topic receiving 635848 citations. The topic is also known as: Shock waves & shockwave.

Double-detonation supernovae of sub-Chandrasekhar mass white dwarfs

Abstract: In the "double-detonation sub-Chandrasekhar" model for type Ia supernovae, a carbon-oxygen (C + O) white dwarf accumulates sufficient amounts of helium such that a detonation ignites in that layer before the Chandrasekhar mass is reached. This detonation is thought to trigger a secondary detonation in the C + O core. By means of one- and two-dimensional hydrodynamic simulations, we investigate the robustness of this explosion mechanism for generic 1-M_sun models and analyze its observable predictions. Also a resolution dependence in numerical simulations is analyzed. The propagation of thermonuclear detonation fronts, both in helium and in the carbon-oxygen mixture, is computed by means of both a level-set function and a simplified description for nuclear reactions. The decision whether a secondary detonation is triggered in the white dwarf's core or not is made based on criteria given in the literature. In a parameter study involving different initial flame geometries for He-shell masses of 0.2 and 0.1 M_sun, we find that a secondary detonation ignition is a very robust process. Converging shock waves originating from the detonation in the He shell generate the conditions for a detonation near the center of the white dwarf in most of the cases considered. Finally, we follow the complete evolution of three selected models with 0.2 M_sun of He through the C/O-detonation phase and obtain nickel-masses of about 0.40 to 0.45 M_sun. Although we have not done a complete scan of the possible parameter space, our results show that sub-Chandrasekhar models are not good candidates for normal or sub-luminous type Ia supernovae. The chemical composition of the ejecta features significant amounts of nickel in the outer layers at high expansion velocities, which is inconsistent with near-maximum spectra. (abbreviated)

Quasi-parallel shocks: A patchwork of three-dimensional structures

Abstract: Collisionless shocks at quasi-parallel geometries, i.e., for which the average magnetic field direction upstream of the shock is close to the shock normal, reveal temporally varying quantities, a variety of boundary crossing and kinetic signatures, and magnetic structures, often convecting, of finite extent. These results can be put together by a framework in which the shock can be viewed as an extended region containing three-dimensional Short Large Amplitude Magnetic Structures (SLAMS) which represent individual semi-cycles of the ambient upstream low frequency waves associated with diffuse ions in the ULF foreshock. As SLAMS convect with the flow they grow to large amplitudes and entrain inter-SLAMS regions to form an inhomogeneous downstream state. Their finite transverse extent is probably related to, and interacts with, ion beams, to produce a patchy transition zone which accounts for the variety of spacecraft signatures observed.

Observations of short large-amplitude magnetic structures at a quasi-parallel shock

Abstract: Results of a detailed analysis of short large-amplitude magnetic structures (SLAMS) observed at an encounter of the quasi-parallel blow shock by the AMPTE UKS and IRM satellites are presented. Isolated SLAMS, surrounded by solar wind conditions, and embedded SLAMS, which lie within or form the boundary with regions of significant heating and deceleration, are identified. The duration, polarization, and other characteristics of SLAMS are all consistent with their growth directly out of the ULF wave field, including the common occurrence of an attached whistler as found in ULF shocklets. The plasma rest frame propagation speeds and two-spacecraft time delays for all cases show that the SLAMS attempt to propagate upstream against the oncoming flow, but are convected back downstream. The speeds and delays vary systematically with SLAMS amplitude in the way anticipated from nonlinear wave theory, as do their polarization features. Inter-SLAMS regions and boundary regions with solar wind contain hot deflected ions of lesser density than within the SLAMS.

Relativistic Detonation Waves and Bubble Growth in False Vacuum Decay

Abstract: After reviewing the current understanding of relativistic shock waves, a detailed analysis of relativistic detonation waves is presented. It is proposed that the motion of a detonation wave is analogous to the growth of a bubble nucleated during false vacuum decay at finite temperatures. Some possible applications of these results to cosmology are discussed.

On the formation of auroral arcs and acceleration of auroral electrons

Abstract: It is suggested that the highly structured auroral arc is caused by a current-driven laminar electrostatic shock oblique to the geomagnetic field. Electrons are accelerated by the potential jump associated with the shock. The shock is assumed to be confined to a plane. Self-consistent solutions to the Poisson-Vlasov systems are calculated for the electrostatic potential. Adiabatic theory is used to calculate the ion number density in terms of the electrostatic potential and its derivatives. The electrons are assumed to be highly magnetized so they can only move parallel to the magnetic field. Solutions are exhibited for two plasma models: (1) streaming electrons and a two-temperature distribution of ions and (2) streaming electrons and ions and thermal electrons and ions. In the latter model, solutions can be obtained for an arbitrary potential jump across the shock. The shock is identified with the linear electrostatic ion cyclotron wave, and stability of these waves is examined to determine conditions for the formation of oblique shocks. Finally, the theory is discussed in the context of the magnetosphere, and possible model shocks are exhibited and discussed in terms of auroral arc formation.