| Full text | |
| Author(s): |
Total Authors: 4
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| Affiliation: | [1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil
[2] Univ Estadual Campinas, Inst Matemat Estat & Comp Cient, BR-13083859 Campinas, SP - Brazil
[3] Univ Wisconsin, Dept Astron, Madison, WI 53706 - USA
Total Affiliations: 3
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| Document type: | Journal article |
| Source: | ASTROPHYSICAL JOURNAL; v. 777, n. 1 NOV 1 2013. |
| Web of Science Citations: | 20 |
| Abstract | |
In order for a molecular cloud clump to form stars, some transport of magnetic flux is required from the denser internal regions to the outer regions; otherwise, this can prevent the gravitational collapse. Fast magnetic reconnection, which takes place in the presence of turbulence, can induce a process of reconnection diffusion that has been elaborated on in earlier theoretical works. We have named this process turbulent reconnection diffusion, or simply RD. This paper continues our numerical study of this process and its implications. In particular, we extend our studies of RD in cylindrical clouds and consider more realistic clouds with spherical gravitational potentials (from embedded stars); we also account for the effects of the gas self-gravity. We demonstrate that, within our setup reconnection, diffusion is efficient. We have also identified the conditions under which RD becomes strong enough to make an initially subcritical cloud clump supercritical and induce its collapse. Our results indicate that the formation of a supercritical core is regulated by a complex interplay between gravity, self-gravity, the magnetic field strength, and nearly transonic and trans-Alfvenic turbulence; therefore, it is very sensitive to the initial conditions of the system. In particular, self-gravity helps RD and, as a result, the magnetic field decoupling from the collapsing gas becomes more efficient compared with the case of an external gravitational field. Our simulations confirm that RD can transport magnetic flux from the core of collapsing clumps to the envelope, but only a few of them become nearly critical or supercritical sub-Alfvenic cores, which is consistent with the observations. Furthermore, we have found that the supercritical cores built up in our simulations develop a predominantly helical magnetic field geometry that is also consistent with recent observations. Finally, we have also evaluated the effective values of the turbulent RD coefficient in our simulations and found that they are much larger than the numerical diffusion coefficient, especially for initially trans-Alfvenic clouds, thus ensuring that the detected magnetic flux removal is due to the action of turbulent RD rather than numerical diffusivity. (AU) | |
| FAPESP's process: | 06/50654-3 - Investigation of high energy and plasma astrophysics phenomena: theory, observation, and numerical simulations |
| Grantee: | Elisabete Maria de Gouveia Dal Pino |
| Support type: | Research Projects - Thematic Grants |
| FAPESP's process: | 09/54006-4 - A computer cluster for the Astronomy Department of the University of São Paulo Institute of Astronomy, Geophysics and Atmospheric Sciences and for the Cruzeiro do Sul University Astrophysics Center |
| Grantee: | Elisabete Maria de Gouveia Dal Pino |
| Support type: | Multi-user Equipment Program |