Advertisement

Formation and structure of magnetized protostellar jets

  • Christian Fendt
  • Max Camenzind
Part V: Outflows—Theory
Part of the Lecture Notes in Physics book series (LNP, volume 465)

Abstract

Protostellar jets most probably originate in the closest environment of a fully convective young stellar object which presumably carries a magnetosphere built up by a strong stellar dynamo and is surrounded by an accretion disk. Interaction between the magnetic field and the accretion disk leads to the formation of a gap between the stellar surface and the disk. The observed jet opening angles may be less than 5°.

We present numerical solutions treeting the relativistic 2D force-balance of the magnetic field, described by the Grad-Schlüter-Shafranov (GSS) equation, and the steady motion of a cold plasma flow along the calculated magnetic flux surfaces in the collimation domain of the jet. Our model takes into account the topology of the star-disk-jet scenario mentioned above. The resulting flows have a finite asymptotic jet radius. From the observed rotational periods of T Tauri stars it follows that the derived light cylinder of a stellar magnetosphere is of the order of the observed jet radii. This fact requires a relativistic treatment although the jet velocities are clearly non-relativistic.

The resulting magnetic field structure allows simultaneously for wind outflow towards an asymptotically cylindrical jet and for mass accretion towards the central star along dipolar field lines. The outflow is initially poorly collimated near the source with an opening angle of 65° and then rapidly collimates within a distance of 0.3 jet radii along the jet axis.

The 2D velocity structure of the flow along the flux surfaces strongly depends on the magnetization σ of the plasma flow. For the asymptotic poloidal jet velocity u we find a power law u .=Acσ 1/3 Since the factor A≥1, this implies that the acceleration along the collimated flux surfaces is more efficient than in a purely conical magnetic structure. The asymptotic fast-magnetosonic Mach-number of the flow turned out to be independent of the magnetization and generally is of the order of 2.5. This has far-reaching consequences for the interpretation of the knot-spacing in protostellar jets.

Keywords

Accretion Disk Flux Surface Stellar Surface Magnetic Field Structure Stellar Magnetic Field 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Appenzeller, I., Mundt, R. (1989), A&AR, 1, 291ADSGoogle Scholar
  2. Appl, S., Camenzind, M. (1992), A&A, 256, 354ADSGoogle Scholar
  3. Appl, S., Camenzind, M. (1993a), A&A, 270, 71ADSGoogle Scholar
  4. Appl, S., Camenzind, M. (1993b), A&A, 274, 699ADSGoogle Scholar
  5. André, P., Phillips, R.B., Lestrade, J.-F., Klein, K.L. (1991), ApJ, 376, 630CrossRefADSGoogle Scholar
  6. Blandford, R.D., Payne, D.G. (1982), MNRAS, 199, 883ADSzbMATHGoogle Scholar
  7. Bouvier, J., Cabrit, S., Fernandez, M., Martin, E.L., Matthews, J.M. (1993), A&A, 272, 176ADSGoogle Scholar
  8. Camenzind, M. (1986), A&A, 162, 32ADSzbMATHGoogle Scholar
  9. Camenzind, M. (1987), A&A, 184, 341ADSzbMATHGoogle Scholar
  10. Camenzind, M. (1990), Magnetized disk-winds and the origin of bipolar outflows, in: Klare, G. (ed) Rev. Mod. Astron., 3, Springer, Heidelberg, p. 234Google Scholar
  11. Camenzind, M., Fendt, C., Paatz, G. (1994), in preparationGoogle Scholar
  12. Chiueh, T., Li, Z., Begelmann, M.C. (1991), ApJ, 377, 462CrossRefADSGoogle Scholar
  13. Fendt, C. (1994), PhD thesis, University of HeidelbergGoogle Scholar
  14. Fendt, C., Camenzind, M., Appl, S. (1994), A&A, 300, 791ADSGoogle Scholar
  15. Fendt, C., Camenzind, M. (1995), in preparationGoogle Scholar
  16. Gahm, G.F., Gullbring, E., Fischerström, C., Lindroos, K.P., Lodén, K. (1993), A&A Suppl. Series, 100, 371ADSGoogle Scholar
  17. Gosh, P., Lamb, F.K. (1978), ApJ, 223, L83CrossRefADSGoogle Scholar
  18. Heyvaerts, J., Norman, C.A. (1989), ApJ, 347, 1055CrossRefMathSciNetADSGoogle Scholar
  19. Königl, A. (1991), ApJ, 370, L39CrossRefGoogle Scholar
  20. Michel, F.C. (1973), ApJ, 180, 207CrossRefADSGoogle Scholar
  21. Michel, F.C. (1991), Theory of neutron star magnetospheres, The University of Chicago Press, ChicagoGoogle Scholar
  22. Montmerle, T., Feigelson, E.D., Bouvier, J., André, P. (1993), Magnetic fields, activity and circumstellar material around young stellar objects, in: Levy,E.H., Lunine, J.I. (eds) Protostars and Planets III, The University of Arizona Press, p. 689Google Scholar
  23. Morse, J.A., Hartigan, P., Cecil, G., Heathcote, S., Raymond, J.C. (1992), ApJ, 399, 231CrossRefADSGoogle Scholar
  24. Morse, J.A., Heathcote, S., Cecil, G., Hartigan, P., Raymond, J.C. (1993), ApJ, 410, 764CrossRefADSGoogle Scholar
  25. Mundt, R., Brugel, E.W., Bührke, T. (1987), ApJ, 319, 275CrossRefADSGoogle Scholar
  26. Mundt, R., Ray, T.P., Bührke, T., Raga, A.C., Solf, J. (1990), A&A, 232, 37ADSGoogle Scholar
  27. Paatz, G., Camenzind, M. (1994), submitted to A&AGoogle Scholar
  28. Pelletier, G., Pudritz, R. (1992), ApJ, 394, 117CrossRefADSGoogle Scholar
  29. Pudritz, R., Norman, C.A. (1983), ApJ, 274, 677CrossRefADSGoogle Scholar
  30. Reipurth, B. (1989), A&A, 220, 249ADSGoogle Scholar
  31. Sakurai, N.I. (1985), A&A, 152, 121zbMATHADSGoogle Scholar
  32. Sakurai, N.I. (1987), Publ. Astr. Soc. Japan, 39, 821ADSGoogle Scholar
  33. Sauty, C., Tsinganos, K. (1994), A&A, 287, 893ADSGoogle Scholar

Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • Christian Fendt
    • 1
  • Max Camenzind
    • 2
  1. 1.Lund ObservatoryLundSweden
  2. 2.LandessternwarteHeidelbergGermany

Personalised recommendations