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Thermal Instability and Turbulence in the ISM

Thermal Instability and Turbulence in the ISM. Alexei Kritsuk CASS/UCSD. Outline. TI basics TI-induced turbulence Sustaining turbulence with variable heating source Scaling relations for multiphase turbulence Thermal pancakes with AMR. TI Theory Highlights. ADS citations.

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Thermal Instability and Turbulence in the ISM

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  1. Thermal Instability and Turbulence in the ISM Alexei Kritsuk CASS/UCSD

  2. Outline • TI basics • TI-induced turbulence • Sustaining turbulence with variable heating source • Scaling relations for multiphase turbulence • Thermal pancakes with AMR

  3. TI Theory Highlights ADS citations • Linear stability of thermal equilibrium [Field 1965] 546 • Generic linear stability [Hunter 1970,71] 10 • Phase equilibrium [Zel’dovich & Pikel’ner 1969] (62) • Nonlinear thermal waves [Doroshkevich & Zel’dovich1981] 12 • Thermal pancakes [Sasorov 1988] (10) • Complexity from TI [Elphick et al. 1991] 16 • Two-phase model [FGH 1969] 419 • Three-phase model [McKee & Ostriker 1977] 973 ( … ) Web of Knowledge

  4. TI Equations

  5. TI-induced TurbulenceApJL 569, L127 (2002)

  6. TI-induced Turbulencelow-density

  7. What’s Happening?

  8. Phase Diagram

  9. Phase Diagrams

  10. Mach number vs. Density

  11. Phase Transitions Stimulated by Time-dependent HeatingApJL 580, L51 (2002)

  12. Interstellar Phase Transitionsresponse to time-dependent local FUV field Low-density region High-density region

  13. Time Evolution of Global Variables

  14. Phase Diagramlow-density

  15. Phase Fractionslow-density

  16. Phase Diagramhigh-density

  17. Energy Exchangehigh-density

  18. Scaling Relations for Turbulence in Multiphase ISMApJL in press (Jan 2004)

  19. TI-induced Turbulencehigh-density

  20. Phase Diagram

  21. Phase Fractions

  22. Velocity Power Spectraat 0.12, 0.56, 1.5, and 2.5 Myr Kolmogorov Burgers total compressional solenoidal

  23. Velocity Structure Functions

  24. Velocity Structure Functionsat 0.5 Myr (order 1, …, 6) longitudinal transverse

  25. Scaling Exponents for velocity structure functions

  26. Initial Rapid Cooling Stage

  27. Structures within a slice at 0.12 Myr Log density Div u Log(|rot u|)

  28. Structures at 0.12 Myr divergence density vorticity pressure

  29. Structures at 0.12 and 0.56 Myr Log density Log | rot (u) | 0.12 2.5

  30. Mach number vs. density at 0.56 Myr Threshold density

  31. Scaling Exponents at 0.56 Myr

  32. Work in progress…

  33. Thermal Pancakes with AMR

  34. Thermal Pancakes with AMR

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