Thermal Instability and Thermal Instability and Turbulence in the ISMTurbulence in the ISM

Alexei KritsukAlexei KritsukCASS/UCSDCASS/UCSD

OutlineOutline

TI basicsTI basics

TI-induced turbulenceTI-induced turbulence

Sustaining turbulence with variable heating Sustaining turbulence with variable heating sourcesource

Scaling relations for multiphase turbulenceScaling relations for multiphase turbulence

Thermal pancakes with AMRThermal pancakes with AMR

TI Theory HighlightsTI Theory Highlights Linear stability of thermal equilibrium Linear stability of thermal equilibrium [Field 1965] 546[Field 1965] 546

Generic linear stability Generic linear stability [Hunter 1970,71] 10[Hunter 1970,71] 10

Phase equilibrium Phase equilibrium [Zel’dovich & Pikel’ner 1969] (62) [Zel’dovich & Pikel’ner 1969] (62)

Nonlinear thermal waves Nonlinear thermal waves [Doroshkevich & Zel’dovich[Doroshkevich & Zel’dovich 1981] 121981] 12

Thermal pancakes Thermal pancakes [Sasorov 1988] (10)[Sasorov 1988] (10)

Complexity from TI Complexity from TI [Elphick et al. 1991] 16[Elphick et al. 1991] 16

Two-phase model Two-phase model [FGH 1969] 419[FGH 1969] 419

Three-phase model Three-phase model [McKee & Ostriker 1977] 973[McKee & Ostriker 1977] 973

ADS citations

( … ) Web of Knowledge

TI EquationsTI Equations

TI-induced TurbulenceTI-induced TurbulenceApJL 569, L127 (2002)ApJL 569, L127 (2002)

TI-induced TurbulenceTI-induced Turbulencelow-densitylow-density

What’s Happening?What’s Happening?

Phase DiagramPhase Diagram

Phase DiagramsPhase Diagrams

Mach number vs. DensityMach number vs. Density

Phase Transitions Stimulated by Phase Transitions Stimulated by Time-dependent HeatingTime-dependent Heating

ApJL 580, L51 (2002)ApJL 580, L51 (2002)

Interstellar Phase TransitionsInterstellar Phase Transitionsresponse to time-dependent local FUV fieldresponse to time-dependent local FUV field

Low-density regionLow-density region High-densityHigh-density region region

Time Evolution of Global VariablesTime Evolution of Global Variables

Phase DiagramPhase Diagramlow-densitylow-density

Phase FractionsPhase Fractionslow-densitylow-density

Phase DiagramPhase Diagramhigh-densityhigh-density

Energy ExchangeEnergy Exchangehigh-densityhigh-density

Scaling Relations for Turbulence in Scaling Relations for Turbulence in Multiphase ISMMultiphase ISMApJL in press (Jan 2004)ApJL in press (Jan 2004)

TI-induced TurbulenceTI-induced Turbulencehigh-densityhigh-density

Phase DiagramPhase Diagram

Phase FractionsPhase Fractions

Velocity Power SpectraVelocity Power Spectraat 0.12, 0.56, 1.5, and 2.5 Myrat 0.12, 0.56, 1.5, and 2.5 Myr

total compressional solenoidal

Kolmogorov

Burgers

Velocity Structure FunctionsVelocity Structure Functions

Velocity Structure FunctionsVelocity Structure Functionsat 0.5 Myr (order 1, …, 6)at 0.5 Myr (order 1, …, 6)

longitudinal transverse

Scaling Exponents Scaling Exponents for velocity structure functionsfor velocity structure functions

Initial Rapid Cooling StageInitial Rapid Cooling Stage

Structures within a slice at 0.12 MyrStructures within a slice at 0.12 Myr

Log density Div u Log(|rot u|)

Structures at 0.12 MyrStructures at 0.12 Myrde

nsity

vort

icity

dive

rgen

cepr

essu

re

Structures at 0.12 and 0.56 MyrStructures at 0.12 and 0.56 Myr

0.12

2.5

Log density Log | rot (u) |

Mach number vs. density at 0.56 MyrMach number vs. density at 0.56 Myr

Threshold density

Scaling Exponents at 0.56 MyrScaling Exponents at 0.56 Myr

Work in progress…Work in progress…

Thermal Pancakes with AMRThermal Pancakes with AMR

Thermal Pancakes with AMRThermal Pancakes with AMR