A “no-drift” runaway pile-up of pebbles in protoplanetary disks in which midplane turbulence increases with radius

A notable challenge of planet formation is to find a path directly form planetesimals from small particles. We aim understand how drifting pebbles pile up in protoplanetary disk with non-uniform turbulence structure. consider structure which the midplane viscosity increasing radius disks as outer region dead zone. perform 1D diffusion-advection simulations that include back-reaction (the inertia) radial drift and vertical/radial diffusion for given pebble-to-gas mass flux. report new mechanism, "no-drift" runaway pile-up, leading accumulation disks, thus favoring by streaming and/or gravitational instabilities. This occurs when entering zone experience decrease vertical turbulence. The scale height pebble subdisk then decreases, enough values high gas flux ratio, on leads significant their velocity progressive accumulation. ratio large so effect dominates over any Kelvin-Helmholtz shear instability. process independent existence pressure bump.