“Ashfall” Induced by Molecular Outflow in Protostar Evolution

Dust growth and its associated dynamics play key roles in the first phase of planet formation young stellar objects. Observations have detected signs dust very protoplanetary disks. Furthermore, formation, gaps disk at a distance several tens au from central protostar, are also reported. From theoretical point view, however, outer regions is difficult due to rapid inward drift dust, called radial barrier. Here, on basis three-dimensional magnetohydrodynamical simulations evolution with growth, we propose mechanism "ashfall" phenomenon, induced by powerful molecular outflow driven magnetic field that may circumvent We find large grows size about centimeter inner region entrained an disk. Then, decoupled gas ejected centrifugal force, enriching grown envelope eventually falls onto edge The overall process similar behavior ashfall volcanic eruptions. In Stokes number increases reaccreting less dense edge. This allow grains overcome Consequently, phenomenon can provide crucial assist for making planetesimals possible, hence wide-orbit planets gaps.