Dust-driven vertical shear instability triggers sustained turbulence in isothermal disc simulations without thermal gradients

The study initializes two-fluid equilibria with dust diffusion and then replaces live dust with a fixed, height-dependent drag profile to isolate DVSI from streaming or drag instabilities. Linear growth begins off the midplane where vertical shear peaks, launching short-radial, tall-vertical modes that saturate through Kelvin-Helmholtz parasites, yielding persistent vertical stirring. This mechanism operates in barotropic conditions where classical VSI is suppressed, directly addressing a gap in models that assumed radial temperature gradients were mandatory for VSI-driven accretion.

Prior VSI literature focused on radiative discs or global thermal structure; the DVSI finding implies that dust settling itself can source the shear needed for turbulence even in optically thick, isothermal layers. That changes estimates of vertical mixing rates in the inner few au where streaming instability also operates, potentially altering pebble concentration thresholds and planetesimal formation efficiency. The work therefore bridges local dust dynamics to global disc evolution without invoking additional physics.

Three-dimensional extensions with live dust feedback and non-ideal MHD will be required to test whether DVSI survives or couples to the stratified streaming instability. If the parasitic saturation persists, dust-driven shear becomes a default turbulence source in any settled dust layer, revising both accretion and chemical-transport prescriptions used in population-synthesis models.