The instability of a radiative shock wave in a magnetic field
Tóm tắt
The deceleration of matter in a radioactive shock wave has been mathematically simulated. This problem is relevant to the variable radiancy of T Tauri stars. We assume that an ordered magnetic field at the surface of a star is not too great, i.e., B ≤ 100 G. In this case, the initial deceleration and plasma heating (at the entrance to the cooling zone) occur in a fast magnetohydrodynamic (MHD) shock wave. To calculate the intensity of radiation losses, we use real and power radiative functions. The stability/instability of a radiative shock wave is considered as a function of the incoming flow’s parameters: velocity, strength of the magnetic field, and its inclination to the surface of the star. In a series of calculations with the real radiative function, a simple criterion for stability at an accretion velocity of 1.3 × 107 cm/s has been found. The results of modeling with the real and power radiative functions are compared.
Tài liệu tham khảo
S. A. Lamzin, The Structure of a Shock Wave in Case of Accretion onto Young Stars of small Mass, Azh 75, 367–382 (1998).
A. V. Koldoba, G. V. Ustyugova, M. M. Romanova, and R. V. E. Lovelace, Oscillation of Magnetohydrodynamic Shock Waves on the Surface of T Tauri Stars, MNRAS 388, 357–366 (2008).
V. G. Surdin and S. A. Lamzin, Protostars: Where, How and When Stars Are Formed (Nauka, Moscow, 1992) [in Russian].
N. Bessolaz, C. Zanni, J. Ferreira, et al., Accretion Funnels onto Weakly Magnetized Young Stars, A&A 478, 155–162 (2008).
M. M. Romanova, G. V. Ustyugova, A. V. Koldoba, et al., Magnetohydrodynamic Simulations of Disk-magnetized Star Interactions in the Quiescent Regime: Funnel Flows and Angular Momentum Transport, ApJ 578, 420–438 (2002).
E. Berschinger, On the Structure and Stability of Radiative Shock Waves, ApJ 304, 154–177 (1986).
N. M. Kuznetsov, Stability of Shock Waves, UFN 159(3), 493–527 (1989).
S. P. D’yakov, Stability of Shock Waves, ZhETF 27, 288–295 (1954).
R. A. Chevalier, The Stability of an Accelerating Shock Wave in an Exponential Atmosphere, ApJ 359, 463–468 (1990).
J. J. Erpenbeck, Stability of Idealized One-reaction Detonation, Physics of Floids 7(5), 684–694 (1964).
S. Langer, G. Chanmugan, and G. Shaviv, Thermal Instability in Accretion Flows onto Degenerate Stars, ApJ 245, 23–26 (1981).
R. A. Chevalier and J. N. Imamura, Linear Analysis of an Oscillatory Instability of Radiative Shock Waves, ApJ 261, 543–549 (1982).
B. Ramachandran and M. D. Smith, On the Linear analysis of Unstable Radiative Shocks, MNRAS 357, 707–721 (2005).
B. Ramachandran and M. D. Smith., The Influence of the Mach Number on the Stability of Radiative Shocks, MNRAS 366, 586–608 (2006).
C. J. Saxton, Effect of Lower Boundary Conditions on the Stability of Radiative Shocks, Publ. Astron. Soc. Aust. 19, 282–292 (2002).
A. Mignone, The Dynamics of Radiative Shock Waves: Linear and Nonlinear Evolution, ApJ 626, 373–388 (2005).
M. D. Smith, The Stability of Radiative Shocks, MNRAS 238, 235–252 (1989).
G. Toth and B. T. Draine, Oscillatory Instability of Radiative Shocks with Transverse Magnetic Field: Linear Analysis and Nonlinear Simulations, ApJ 413, 176–189 (1993).
B. Ramachandran and M. D. Smith, A Stability Analysis of Radiative shocks with Transverse Magnetic Field, MNRAS 362, 1353–1362 (2005).
R. Rosner, W. H. Tucker, and G. S. Vaiana, Dynamics of the Quiescent Solar Corona, ApJ SS 220, 643–665 (1978).
J. C. Raymond and B. W. Smith, Soft X-ray Spectrum of Hot Plasma, ApJ SS 35, 419–439 (1977).
G. Peres, R. Rosner, S. Serio, et al., Coronal Closed Structures. IV-Hydrodynamical Stability and Response to Heating Perturbations, ApJ 252, 791–799 (1982).
O. Gnat and A. Sternberg, Time-dependent Ionization in Radiatively Cooling Gas, ApJ SS 168, 213–230 (2007).
M. D. Smith, Compression in Radiative Shocks: Switch and Intermediate Properties, A&A 272, 571 (no data).
A. G. Kukikovskii, N. V. Pogorelov, and A. Yu. Semenov, Mathematical Problems of Numerical Solution of Hyperbolic systems of Equations (Fizmatlit, Moscow, 2001) [in Russian].