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.

Acceleration of >47 keV Ions and >2 keV electrons by interplanetary shocks at 1 AU

Abstract: We present initial results from a survey of the effects of interplanetary shocks on energetic ≥2 keV electrons and ≥47 keV ions, as observed by the field, plasma, and energetic particle experiments on the ISEE 3 spacecraft. Shock normals, velocities, Mach numbers, and upstream and downstream plasma parameters were determined for 37 forward shocks out of a total of 55 shocks observed between August 1978 and November 1979. We find that a minimum shock velocity along the upstream magnetic field of ∼250 km/s is required for an interplanetary shock to have a significant effect on acceleration of ≥2 keV electrons or ≥47 keV ions. Shocks with no effect on the energetic particle populations also had relatively small ratios of downstream to upstream magnetic field magnitudes. These results suggest that magnetostatic reflection off the shock itself is a significant mechanism in the acceleration process. Both energetic electron and ion flux variations associated with shocks can be classified into four general types: (1) no significant variation at all, (2) a spike of a few minutes duration at or near the shock, (3) a steplike postshock increase, and (4) a slow rise beginning several hours before the shock (energetic storm particle event). Essentially, every quasi-perpendicular shock with θBn ≳ 70° produced a shock spike in the proton fluxes, while every quasi-parallel shock (θBn ≲ 50°) produced a proton energetic storm particles event, provided the shock velocity was greater than the above stated threshold. Electron spikes were also observed for most, but not all, shocks with θBn ≳ 70°. The most common effect observed in the electron fluxes was a steplike postshock increase of a factor of ∼2. These had no obvious dependence on θBn, but were found for every shock with speed greater than ∼175 km/s. Shock effects in the electron fluxes were about as common as for protons, but were limited to the 2–10 keV energy range except for 3 events which extended up to ∼50 keV. We find that significant ambient populations of both ≥2 keV electrons and ≳47 keV ions are present in the interplanetary medium prior to every shock. These particles could be the “seed” particles for the shock acceleration.

Microimplosions: cavitation collapse and shock wave emission on a nanosecond time scale

Abstract: A streak camera with high spatial and temporal resolution was used for imaging the dynamics of the violent collapse in single-bubble sonoluminescence The high pressure in the last phase of the bubble collapse leads to the emission of a shock wave, which is launched with a shock velocity of almost 4000 m/s The shock amplitude decays much faster than approximately 1/r From the strongly nonlinear propagation the pressure in the vicinity of the bubble can be calculated to be in the range of 40-60 kbar

A facility for gas- and condensed-phase measurements behind shock waves

Abstract: A shock-tube facility consisting of two, single-pulse shock tubes for the study of fundamental processes related to gas-phase chemical kinetics and the formation and reaction of solid and liquid aerosols at elevated temperatures is described. Recent upgrades and additions include a new high-vacuum system, a new gas-handling system, a new control system and electronics, an optimized velocity-detection scheme, a computer-based data acquisition system, several optical diagnostics, and new techniques and procedures for handling experiments involving gas/powder mixtures. Test times on the order of 3 ms are possible with reflected-shock pressures up to 100 atm and temperatures greater than 4000 K. Applications for the shock-tube facility include the study of ignition delay times of fuel/oxidizer mixtures, the measurement of chemical kinetic reaction rates, the study of fundamental particle formation from the gas phase, and solid-particle vaporization, among others. The diagnostic techniques include standard differential laser absorption, FM laser absorption spectroscopy, laser extinction for particle volume fraction and size, temporally and spectrally resolved emission from gas-phase species, and a scanning mobility particle sizer for particle size distributions. Details on the set-up and operation of the shock tube and diagnostics are given, the results of a detailed uncertainty analysis on the accuracy of the test temperature inferred from the incident-shock velocity are provided, and some recent results are presented.