Astrophysical Aspects of High-Energy-Density Physics

Transcription

1 Astrophysical Aspects of High-Energy-Density Physics D.D. Ryutov Lawrence Livermore National Laboratory, Livermore, CA Presented at HEDP Summer School, UC Berkeley, August 8-13, 2005

2 Interaction between physics and astrophysics has always been mutually beneficial Kepler s laws Newton s gravity law Einstein s E= mc 2 Gamov s conjecture Bethe s theory of the (4H He) stellar energy source

3 High-Energy-Density (HED) laboratory physics astrophysics HED laboratory experiments provide information about some important input parameters for astrophysical modeling - Opacities - Equations of state Dynamical laboratory experiments allow benchmarking astrophysical hydrodynamical codes under scalable conditions - Hydrodynamics of supernovae explosions - Astrophysical jets - Hydrodynamics of photoevaporation fronts - Particle acceleration in Z pinches Laboratory experiments may prompt the emergence of new concepts in astrophysics, and vice versa

4 Astrophysics High-Energy-Density (HED) laboratory physics? Bullets? Hydrodynamics at very high Reynolds numbers?

5 Opacities Heat transport in stars is normally dominated by radiative transport. Photons experience a random walk, being absorbed and re-emitted by non-fully-stripped atoms (the stars are made not only of hydrogen!) The number of atomic transitions involved may be very large The absorption-radiation processes are affected by the plasma density, temperature, and velocity shear a very complicated set of equations! The laboratory experiments with intense lasers and Z pinches help in benchmarking and correcting the codes describing these effects in the astrophysics-relevant conditions P.T. Springer et al., J. Quant. Spectrosc. Radiat. Transfer 58, 927 (1997); C.A. Iglesias, F.J. Rogers. ApJ 371, L73 (1991).

6 Stars are made not only of hydrogen Credit: Hugh Rollinson, U. of Gloucestershire, UK

7 Experiment on measuring of opacity for iron (important for the theory of stellar envelopes) P.T. Springer et al, J.Quant. Spectrosc. Radiat. Transfer, 58, 927 (1997) These experiments were performed at the Saturn Z-pinch facility at Sandia (see lecture by Deeney)

8 Equations of State (EOS) p=p(ρ,t) [an ideal gas: p=k B (ρ/µ)t] Is important when the equilibrium is considered: dp dr EOS r r G dt = g g= 2 4π r r dr = 2 ρ ; 4π ρ( ) ; κ qr ( ) r dr 2 2 r dr r 0 For normal stars (like our Sun), the ideal gas approximation (with effects of degeneracy included) is good, except for the very central part. For the giant planets, like Jupiter, is far from being ideal and is difficult to calculate. Here, the HED experiments provide direct information. Equations of state for hydrogen have been measured in the HED experiments with lasers and Z-pinches G.W. Collins, et al. Science, 281, 1178 (1998); M.D. Knudson, et al. Phys. Rev. Lett., 90, (2003). More details in the lecture by Collins opacity 0

9 High-Energy-Density (HED) laboratory physics astrophysics HED laboratory experiments provide information about some important input parameters for astrophysical modeling - Opacities - Equations of state Dynamical laboratory experiments allow benchmarking astrophysical hydrodynamical codes under scalable conditions - Hydrodynamics of supernovae explosions - Astrophysical jets - Hydrodynamics of photoevaporation fronts - Particle acceleration in Z pinches Laboratory experiments may prompt the emergence of new concepts in astrophysics, and vice versa

10 Merits of the laboratory experiments on astrophysical hydrodynamics In the laboratory, it is possible to - Vary initial conditions in a controlled way - Repeat an experiment many times - Equip it with as many diagnostics as needed During the last 5 years, many successful experiments have been done (mostly, with intense lasers) Reviews: Remington B A, Drake R P, Takabe H, Arnett D Science, 284, 1488 Remington B A, Drake R P, Takabe H, Arnett D Phys. Plasmas, 7, Drake, R.P. J. Geophys. Res., 104, 14,505-14,515 (1999). Takabe, H.. Progr. Theor. Phys. Suppl. # 143, 205 (2001)

11 Astrophysical objects have large dimensions and evolve slowly E. Muller et al., AA, 251, 505(1991) Core- E. Michael et al, ApJ, 492, L143 (1998) Interaction of collapse SN explosion, 2000s, cm SN ejecta with the ambient medium (HST image), ~10 yr, cm S. Heathcote et al., AJ, 112, 1141 (1996) Herbig-Haro jets (HST image), cm, 1000 yr OUTLINE J. Hester et al., AJ, 111, 2349 (1996) Photoevaporated molecular clouds (HST image), cm, 10 5 yr

12 In the laboratory laser experiments, spatial scales are small (~ 100 µm) and time-scales are short (~ 10 ns) This requires scalability over 24 orders of magnitude in spatial dimensions and time duration! 0.8 mm experiment simulation H.F. Robey, et al. Phys. Plasmas, 8, 2446, 2001

13 SIMILARITY CONSIDERATIONS Equations of compressible hydrodynamics: dρ + ρ v = 0; dt dv 2 d ρ = p + η v; + v dt dt t dp + γp v = 0. dt

14 Consider the initial-value problem: ρ L* ρ = ρ* f r p = p g L * ; * r L * ; t = 0 t = 0 ρ v = h r t = 0 v * L *. x These initial conditions are set by 3 (6) dimensionless functions, f, g, h, and 4 dimensional parameters: L*, ρ*, p*, v*.

15 Introduce dimensionless (primed) variables: r t r = t = = r t p= p p r t v= v r t L * ; v * ; ρ ρ* ρ(, ); * (, ); v * (, ) L * Substitute them into the hydrodynamic equations: dρ ρ* v* dρ ρ* v* + ρ v = 0; ρ ; dt L * dt + L * v = 0 2 dv 2 ρ * v* dv p * ηv* ρ = p + η v; ρ p dt L * dt = L * + L * 2 v; 2 dp p* v* dp p* v* + γp v = 0. γp. dt L * dt + L * v = 0 1/Eu 2 Eu=Euler Number 1/Re Re=Reynolds Number dρ dt + ρ v = 0; dv p p dt = * + η L 2 ρ v; 2 ρ * v* ρ * v* * dp p dt + γ v = 0.

16 The two systems evolve in the identical way (up to the corresponding scaling factors, i.e., the choice of the particular values of L*, ρ*, p*, v*, and B*) if the initial conditions are geometrically similar, and two numbers, Eu and Re, are the same for the two systems Eu v * ρ */ p *; Re ρ * v * L * η [Ryutov D D, Drake R P, Kane J O, Liang E, Remington B A, and Wood-Vasey W M. Astrophysical Journal, 518, 821 (1999). Ryutov D D, Remington B A, Robey H F, Drake R P. Phys. Plasmas, 8, 1804 (2001).] A very broad similarity: only two constraints on four scaling factors (L*, ρ*, p*, v*) characterizing the initial state SHOCKS ARE ALLOWED! [Ryutov D D, Drake R P, and Remington B A. Astrophysical Journal - Supplement, 127, 465 (2000)]

17 Steps in developing a scaled experiment 1. Establish that the basic equations describing the two systems are identical 2. Make a dimensional analysis and find similarity transformations 3. Determine the way of creating proper initial conditions in the laboratory experiment 4. Establish the time interval within which the similarity indeed holds, with the limits set either because of the effect of the boundaries inevitably present in the laboratory experiment, or because of development of small-scale motions which may bring up new physics not properly reflected by the initial equations. [Sometimes, establishing the similarity between two systems is understood (wrongly) as #2 only: a dimensional analysis of the corresponding equations.]

18 Hydrodynamics of Supernovae explosions A particular problem: instability of a He-H interface in a corecollapse supernova (J. Kane et al., Phys. Plasmas, 6, 2065, 1999). - The shock wave reaches the He-H transition zone ( interface ) in ~500s - This interface becomes RT (Rayleigh-Taylor) unstable. interface H He Exploded core shock

19 In the laboratory experiment, drive a strong shock through a rippled interface between copper and plastic layers. Ablated material shock Incident light Cu Publications on scaled laboratory experiments relevant to SN hydrodynamics: B.A. Remington et al. Phys. Plasmas, 4, 1994 (1997); H.F. Robey et al. Phys Plasmas, 8, 2446 (2001); R.P. Drake et al. Ap. J. 564, 896 (2002) CH

20 E. Muller et al., AA, 251, 505(1991) Why important: sheds the light on the problem of the early appearance of heavy elements in the SN photosphere H.F. Robey, et al. Phys. Plasmas, 8, 2446, 2001

21 High-Energy-Density (HED) laboratory physics astrophysics HED laboratory experiments provide information about some important input parameters for astrophysical modeling - Opacities - Equations of state Dynamical laboratory experiments allow benchmarking astrophysical hydrodynamical codes under scalable conditions - Hydrodynamics of supernovae explosions - Astrophysical jets - Hydrodynamics of photoevaporation fronts - Particle acceleration in Z pinches Laboratory experiments may prompt the emergence of new concepts in astrophysics, and vice versa

22 Astrophysical jets S. Heathcote et al., AJ, 112, 1141 (1996) Herbig-Haro jets (Hubble Space Telescope image), cm, 1000 yr Similar objects (although at a 18 orders of magnitude smaller scale!) have been reproduced in the laboratory experiments with lasers and Z pinches

23 Generating jets with a pulsed-power (Z-pinch) technology 2 1 Cathode Anode

24 An experiment on the MAGPIE Z-pinch machine at Imperial College (London) Courtesy S.V. Lebedev, Imperial College, London (MNRAS, 361, 97, 2005)

25 High-Energy-Density (HED) laboratory physics astrophysics HED laboratory experiments provide information about some important input parameters for astrophysical modeling - Opacities - Equations of state Dynamical laboratory experiments allow benchmarking astrophysical hydrodynamical codes under scalable conditions - Hydrodynamics of supernovae explosions - Astrophysical jets - Hydrodynamics of photoevaporation fronts - Particle acceleration in Z pinches Laboratory experiments may prompt the emergence of new concepts in astrophysics, and vice versa

26 Hydrodynamics of photoevaporation (ablation) fronts Eagle Nebula: a cold molecular cloud illuminated by young O-type stars. The ionizing radiation from the stars generates a strong ablation flow from the surface of the cloud Courtesy of M. Pound, University of Maryland

27 Historically the first model of pillar formation (L. Spitzer, 1954): ablation front ( Rayleigh-Taylor) instability g Ablation flow Incident radiation

28 The Rayleigh-Taylor instability of the ablation front leads to formation of the bubble-and-spike structure L. Spitzer, 1954 Eagle Nebula (HST Image)

29 Laboratory experiments on the ablation front instability (Remington B A, Weber S V, Haan S W, Kilkenny J D, Glendinning S G, Wallace R J, Goldstein W H, Wilson B G, Nash J K 1993 Phys. Fluids B5 2588)

30 (HED) laboratory physics astrophysics HED laboratory experiments provide information about some important input parameters for astrophysical modeling - Opacities - Equations of state Dynamical laboratory experiments allow benchmarking astrophysical hydrodynamical codes under scalable conditions - Hydrodynamics of supernovae explosions - Astrophysical jets - Hydrodynamics of photoevaporation fronts - Particle acceleration in Z pinches Laboratory experiments may prompt the emergence of new concepts in astrophysics, and vice versa

31 Cosmic rays vs particle beams in Z pinches Ion trajectory B Acceleration by shock waves Shock front Turbulence generated by pulsars Astrophysical pinches Z-pinch disruption

32 The morphology of some astrophysical objects clearly points at the presence of the magnetic field on the galactic scales The image of filaments near the center of our galaxy at the wavelength 20 cm. The length of the arcs is ~ 30 pc (courtesy F Yusef-Zadeh and NRAO, Nature, 310, 1984).

33 Mechanisms of ion acceleration in Z pinches (Trubnikov, Vikhrev, Kies, Haines, Rudakov, Sagdeev, ; for the survey see: Ryutov, Derzon, and Matzen, Rev. Mod. Phys., 72, 167, 2000) Adiabatic compression Disruption of the current / T r or T r Microturbulence V fi t d ( LI) dt D f i = 1 2 v v v phonons

34 Summary HED laboratory experiments have become an important source of input data for astrophysical opacities and equations of state First steps have been made in developing scalable experimental models of dynamical astrophysical phenomena (like, e.g., SN explosions) HED experiments have a great potential for simulating the cosmic rays generation A progress in the area of laboratory astrophysics requires a close collaboration between laboratory physicists and astrophysicists at all steps of development of a particular experiment

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