Heating and Ionization of X-Winds

By H. Shang, A. Glassgold, F. Shu, S. Lizano. 2001

134 citations recorded by the source corpus.

In order to compare the X-wind with observations, one needs to be able to calculate its thermal and ionization properties. We formulate the physical basis for the streamline-by-streamline integration of the ionization and heat equations of the steady X-wind. In addition to the well-known processes associated with the interaction of stellar and accretion funnel hot spot radiation with the wind, we include X-ray heating and ionization, mechanical heating, and a revised calculation of ambipolar diffusion heating. The mechanical heating arises from fluctuations produced by star-disk interactions of the time-dependent X-wind that are carried by the wind to large distances where they are dissipated in shocks, MHD waves, and turbulent cascades. We model the time-averaged heating by the scale-free volumetric heating rate, Γmech = αρv3s-1, where ρ and v are the local mass density and wind speed, respectively, s is the distance from the origin, and α is a phenomenological constant. When we consider a partially revealed but active young stellar object, we find that choosing α ~ 10-3 in our numerical calculations produces temperatures and electron fractions that are high enough for the X-wind jet to radiate in the optical forbidden lines at the level and on the spatial scales that are observed. We also discuss a variety of applications of our thermal-chemical calculations that can lead to further observational checks of X-wind theory.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/98f09bd05e9054307496ef6c1dd02ffdc4a4bd2e

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Citations in the corpus

Magnetospheric accretion-ejection processes in the classical T Tauri star AA Tauri (2006, background): “The winds of classical T Tauri stars (CTTSs) have been primarily investigated through the observations and modelling of forbidden emission lines, whose high velocity component originates in spatially extended microjets (Hartigan et al. 1995; Shang et al. 2002).”
Collapse of Magnetized Singular Isothermal Toroids. II. Rotation and Magnetic Braking (2003, background): “Some shaping of such winds, if they start out in a wide-angle configuration (see Shang et al. 2002), might occur, if they, like their low-speed counterparts in Fig.”
On the formation of Hα line emission around classical T Tauri stars (2006, background): “Z CMa and AS 353A) displaying the outflows in larger scale (>50 au); however, this could be formed in shocks rather than MHD-wave heating (e.g. Hartmann et al. 1982) or X-ray heating (e.g. Shang et al. 2002).”
Heating Protoplanetary Disk Atmospheres (2004, methodology): “Shang et al. (2002) found that, in addition to the usual direct X-ray heating energy h1 (in the range 5–15 eV), there is an indirect heating energy h2 that arises from the increase in the population of electronically excited states produced by X-rays and leads to gas heating by collisional…”
Photoevaporation of Circumstellar Disks around Young Stars (2004, background): “Recently doubts have been raised about the possibility of ionizing radiation penetrating the thick protostellar jet, which lies between the star and the disk (Shang et al. 2002).”
Which jet launching mechanism(s) in T Tauri stars (2006, background): “This gives rise to a wide-angle ”X-wind” (Shu et al. 1994; Shang et al. 2002).”
Magnetic Flaring in the Pre-Main-Sequence Sun and Implications for the Early Solar System (2002, background): “FLARING IN YOUNG SUN 343 main-sequence stars (see, e.g., Igea & Glassgold 1999; Aikawa &Herbst 1999; Glassgold, Feigelson, &Montmerle 2000; Shang et al. 2002).”