COUNTERROTATION IN MAGNETOCENTRIFUGALLY DRIVEN JETS AND OTHER WINDS
- Laboratoire Univers et Theories, Observatoire de Paris, UMR 8102 du CNRS, Universite Paris Diderot, F-92190 Meudon (France)
- Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)
- CEA, IRAMIS, Service Photons, Atomes et Molecules, F-91191 Gif-sur-Yvette (France)
- IASA and Section of Astrophysics, Astronomy and Mechanics, Department of Physics, University of Athens, Panepistimiopolis GR-157 84, Zografos (Greece)
Rotation measurement in jets from T Tauri stars is a rather difficult task. Some jets seem to be rotating in a direction opposite to that of the underlying disk, although it is not yet clear if this affects the totality or part of the outflows. On the other hand, Ulysses data also suggest that the solar wind may rotate in two opposite ways between the northern and southern hemispheres. We show that this result is not as surprising as it may seem and that it emerges naturally from the ideal MHD equations. Specifically, counterrotating jets neither contradict the magnetocentrifugal driving of the flow nor prevent extraction of angular momentum from the disk. The demonstration of this result is shown by combining the ideal MHD equations for steady axisymmetric flows. Provided that the jet is decelerated below some given threshold beyond the Alfven surface, the flow will change its direction of rotation locally or globally. Counterrotation is also possible for only some layers of the outflow at specific altitudes along the jet axis. We conclude that the counterrotation of winds or jets with respect to the source, star or disk, is not in contradiction with the magnetocentrifugal driving paradigm. This phenomenon may affect part of the outflow, either in one hemisphere, or only in some of the outflow layers. From a time-dependent simulation, we illustrate this effect and show that it may not be permanent.
- OSTI ID:
- 22078469
- Journal Information:
- Astrophysical Journal Letters, Vol. 759, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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