Dynamical Collapse of Magnetized Molecular Clouds: Formation of Self-Similarly Collapsing Disks

We followed fragmentation of magnetized lamentary clouds and formation of disks with two-dimensional numerical simulations. A lamentary cloud with longitudinal magnetic elds fragments to form geometrically thin disks perpendicular to the magnetic eld. Each disk collapses self-similarly toward the lament axis, keeping quasi-static equilibrium in the direction parallel to the axis. With some simpli cations we obtained an approximate similarity solution for a dynamicallycollapsing disk threaded by the magnetic eld.