When Shock Waves Collide
[1];
[3];
- Rice Univ., Houston, TX (United States). Dept. of Physics and Astronomy
- Atomic Weapons Establishment (AWE), Berkshire (United Kingdom)
- Univ. of Rochester, NY (United States). Dept. of Physics and Astronomy
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- General Atomics, San Diego, CA (United States)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Supersonic outflows from objects as varied as stellar jets, massive stars, and novae often exhibit multiple shock waves that overlap one another. When the intersection angle between two shock waves exceeds a critical value, the system reconfigures its geometry to create a normal shock known as a Mach stem where the shocks meet. Mach stems are important for interpreting emission-line images of shocked gas because a normal shock produces higher postshock temperatures, and therefore a higher-excitation spectrum than does an oblique shock. In this paper, we summarize the results of a series of numerical simulations and laboratory experiments designed to quantify how Mach stems behave in supersonic plasmas that are the norm in astrophysical flows. The experiments test analytical predictions for critical angles where Mach stems should form, and quantify how Mach stems grow and decay as intersection angles between the incident shock and a surface change. While small Mach stems are destroyed by surface irregularities and subcritical angles, larger ones persist in these situations and can regrow if the intersection angle changes to become more favorable. The experimental and numerical results show that although Mach stems occur only over a limited range of intersection angles and size scales, within these ranges they are relatively robust, and hence are a viable explanation for variable bright knots observed in Hubble Space Telescope images at the intersections of some bow shocks in stellar jets.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States); Rice Univ., Houston, TX (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Contributing Organization:
- Rice Univ., Houston, TX (United States); Atomic Weapons Establishment (AWE), Berkshire (United Kingdom); Univ. of Rochester, NY (United States); General Atomics, San Diego, CA (United States)
- Grant/Contract Number:
- NA0001944; NA0002037; NA0002722; AC52-07NA27344
- OSTI ID:
- 1329878
- Alternate ID(s):
- OSTI ID: 1289387; OSTI ID: 1462316
- Report Number(s):
- LA-UR-15-24971; LLNL-JRNL-698500; DOE-Rice-2037-3
- Journal Information:
- The Astrophysical Journal (Online), Vol. 823, Issue 2; ISSN 1538-4357
- Publisher:
- Institute of Physics (IOP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Proper Motions and Shock Wave Dynamics in the HH 7-11 Stellar Jet
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journal | May 2019 |
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Related Subjects
Herbig–Haro objects
hydrodynamics
jets and outflows
atomic laboratory methods
shock waves
stars
jets
42 ENGINEERING
Herbig-Haro objects
ISM: jets and outflows
methods: laboratory: atomic
stars: jets
Herbig–Haro objects – hydrodynamics – ISM: jets and outflows – methods: laboratory: atomic – shock waves – stars: jets