مشخصات پژوهش

In this work, we want to know if the role of the Ohmic resistivity is important in the gravitational collapse of a filamentary molecular cloud. We consider a filamentary molecular cloud undergoing gravitational collapse by using only Ohmic resistivity associated with the non-ideal magnetohydrodynamics (MHD) in the cylindrical coordinate system. In this study, the Ohmic resistivity appears as an important key for the development of the formulation of the problem. The magnetic Reynolds number is used to consider the behaviour of Ohmic resistivity that enables us to scale this important parameter. The problem covers both important cases as isothermal and polytropic cases. When the resistivity coefficient is spatially uniform in the isothermal case, the problem can be solved analytically in terms of both the polynomial and the Bessel functions. Also, in the isothermal case, a criterion for the cloud fragment is obtained analytically that may be helpful in the study of multiple stars. The constant flux-to-mass ratio in the ideal MHD regime is in contrast with the observed mean surface magnetic field of some stars. Our results show that the presence of Ohmic effect results in a variable flux-to-mass ratio in the polytropic case. In addition, the Joule heating rate is strongly dependent on the Ohmic coefficient and is only important in the polytropic case. In fact, the presence of the Ohmic effect is very important for the dynamics of the polytropic collapse of the filamentary clouds.