Numerical origin of the midplane dust-density component

Establish the numerical origin of the additional midplane dust-density component that appears when higher-order spatial reconstruction schemes or more accurate gas Riemann solvers are used in PLUTO particle simulations of the streaming instability.

Background

More accurate Riemann solvers and higher-order reconstruction schemes produce narrower meridional dust-velocity distributions, stronger dust settling, and an additional midplane dust-density component. The paper relates this behavior to differences in vorticity and transverse-momentum treatment, but does not establish the causal mechanism.

References

However, the numerical origin is not yet clear.

— A comparison between particle and fluid approaches for streaming instability in global patch simulations  (2610.09575 - Ostertag et al., 7 Oct 2026) in Section 4.1, “Midplane dust density component”

The influence of this aspect on the presence of an additional midplane dust density component remains unclear and needs to be investigated in future work.

— A comparison between particle and fluid approaches for streaming instability in global patch simulations  (2610.09575 - Ostertag et al., 7 Oct 2026) in Section 4.1, “Midplane dust density component”

Our results of vanishing midplane density component raise another question: How do results from works like or , who constrain the parameter space in (total dust-to-gas mass ratio $Z$, Stokes number $\tau_s$), where disks are expected to show strong clumping, change with even higher resolutions?

— A comparison between particle and fluid approaches for streaming instability in global patch simulations  (2610.09575 - Ostertag et al., 7 Oct 2026) in Section 4.6, “Comparison to other works”