HYPERSONIC BUCKSHOT: ASTROPHYSICAL JETS AS HETEROGENEOUS COLLIMATED PLASMOIDS
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14620 (United States)
- Department of Mathematics, Applied Mathematics Program, University of North Carolina, Chapel Hill, NC 27599 (United States)
Herbig-Haro jets are commonly thought of as homogeneous beams of plasma traveling at hypersonic velocities. Structure within jet beams is often attributed to periodic or 'pulsed' variations of conditions at the jet source. Simulations based on this scenario result in knots extending across the jet diameter. Observations and recent high energy density laboratory experiments shed new light on structures below this scale and indicate they may be important for understanding the fundamentals of jet dynamics. In this paper, we offer an alternative to 'pulsed' models of protostellar jets. Using direct numerical simulations we explore the possibility that jets are chains of subradial clumps propagating through a moving interclump medium. Our models explore an idealization of this scenario by injecting small (r < r {sub jet}), dense ({rho}>{rho}{sub jet}) spheres embedded in an otherwise smooth interclump jet flow. The spheres are initialized with velocities differing from the jet velocity by {approx}15%. We find that the consequences of shifting from homogeneous to heterogeneous flows are significant as clumps interact with each other and with the interclump medium in a variety of ways. Structures which mimic what is expected from pulsed-jet models can form, as can be previously unseen, 'subradial' behaviors including backward facing bow shocks and off-axis working surfaces. While these small-scale structures have not been seen before in simulation studies, they are found in high-resolution jet observations. We discuss implications of our simulations for the interpretation of protostellar jets with regard to characterization of knots by a 'lifetime' or 'velocity history' approach as well as linking observed structures with central engines which produce the jets.
- OSTI ID:
- 21296250
- Journal Information:
- Astrophysical Journal, Vol. 695, Issue 2; Other Information: DOI: 10.1088/0004-637X/695/2/999; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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