Enhanced Pebble Drift Across Planet-Opened Gaps in Windy Protoplanetary Disks

TL;DR

This paper investigates how magnetically driven winds alter the transport of solids across planet-carved gaps in protoplanetary disks, challenging the traditional viscous paradigm. Using two-dimensional multifluid hydrodynamic simulations with a parameterized wind model, the authors quantify how dust filtration and the maximum crossing grain size depend on wind strength and planet mass. They find that wind-driven gas inflow can overcome outer-gap pressure bumps, enabling increasingly larger grains—up to mm sizes in strong winds—to cross into the inner disk, with significant implications for inner-disk dust budgets and circumplanetary disk enrichment. The results highlight a potentially important role for disk winds in planet formation and disk chemistry, while noting the need for 3D MHD follow-up to confirm these effects in more realistic settings.

Abstract

When a giant planet forms in a protoplanetary disks, it carves a gap around its orbit separating the disk into two parts: inner disk and outer disk. Traditional disk accretion models, which assume material transport is driven by viscosity, reveal that the planet-induced gap acts like a filter which blocks large dust grains from flowing into the inner disk. However, there is growing evidence that material transport may be driven by magnetically-driven winds instead. By carrying out a suite of two-dimensional multi-fluid hydrodynamic simulations where wind is implemented with a parameterized model, we explored how dust filtration efficiency and the size of dust grains filtered change in disks where gas accretion is dominated by magnetically-driven winds. We found that the inward gas flow driven by the wind can enable dust to overcome the pressure bump at the outer gap edge and penetrate the planet-induced gap. The maximum size of dust grains capable of penetrating the gap increasing with the wind strength. Notably, we found that when wind is strong (mass loss rate = 1e-7 M_sun/yr), mm-sized grains can penetrate the gap opened by a multi-Jovian-mass planet. Our results suggest that magnetically driven winds can significantly enhance pebble drift and impact planet formation in the inner protoplanetary disk.

Figures (18)

• Figure 1: Example of the restart condition where dust is inserted in the outer disk only. These images show the 2D surface density distribution in polar coordinates, $(r, \phi)$. Both gas and dust surface density is normalized by the initial gas surface density, $\Sigma_{\rm g,0}$, for visualization purpose. The dust surface density is constructed such that all of the dust material is in the outer disk ($r \geq 1.5 r_p$), and in the inner disk it is equal to effectively zero. The dust surface density is scaled up from the true density according to $\epsilon_i$, so that the dust surface density in the outer disk is exactly equal to the gas surface density.
• Figure 2: Two-dimensional surface density distribution in polar coordinates after 1000 orbits of evolution for models without wind. The planet it located at $(R, \phi) = (1.0, 0.0)$. The rows present different planet masses, from left to right: 0.1 M$_{Jup}$, 0.3 M$_{Jup}$, 1.0 M$_{Jup}$, 3.0 M$_{Jup}$. The columns present different fluids: from top to bottom, gas, gas tracer (St = $1 \times 10^{-6}$), 1 $\mu$m, 10 $\mu$m, 100 $\mu$m, and 1 mm. The dust surface density is scaled up from the true density according to $\epsilon_i$.
• Figure 3: Azimuthally-averaged surface density profiles after 1000 orbits of evolution for models without wind, adopting various planet masses: 0.1 M$_{Jup}$ (top left), 0.3 M$_{Jup}$ (top right), 1.0 M$_{Jup}$ (bottom left), 3.0 M$_{Jup}$ (bottom right). The planet is located at $R = 1.0$. Each gas and dust fluid is plotted corresponding to the colors in the figure legend. The dotted line in each panel is the initial gas surface density according to equation \ref{['eqn:surfaced_powerLaw']}. The gas tracer and small dust grains were able to flow inward more efficiently than the larger dust grains; while the large dust grains are trapped in the pressure bump in the outer disk. The dust surface density is scaled up from the true density based on their abundance ($\Sigma_{d,i}/\epsilon_i$) for visualization purposes.
• Figure 4: Two-dimensional surface density distribution in polar coordinates after 1000 orbits of evolution for a $m_p = 1 M_{\rm Jup}$ model with varying wind strength: (from left to right) no wind, $\dot{M}_w = 10^{-9} M_\odot~{\rm yr}^{-1}$, $\dot{M}_w = 10^{-8} M_\odot~{\rm yr}^{-1}$, and $\dot{M}_w = 10^{-7} M_\odot~{\rm yr}^{-1}$. The planet is located at $(R, \phi) = (1.0, 0.0)$. The columns are different fluids in the disk, increasing from top to bottom: gas, gas tracer (St = $1 \times 10^{-6}$), 1 $\mu$m, 10 $\mu$m, 100 $\mu$m, and 1 mm. The dust surface density is scaled up from the true density according to $\epsilon_i$.
• Figure 5: Azimuthally-averaged surface density profiles after 1000 orbits of evolution for models with wind, adopting various mass loss rates: No wind (top left), $\dot {M}_w = 10^{-9} M_\odot yr^{-1}$ (top right), $\dot {M}_w = 10^{-8} M_\odot yr^{-1}$ (bottom left), $\dot {M}_w = 10^{-7} M_\odot yr^{-1}$ (bottom right). The planet is located at $R = 1.0$. Each gas and dust fluid is plotted corresponding to the colors in the figure legend. The dust surface density is scaled up from the true density based on their abundance ($\Sigma_{d,i}/\epsilon_i$) for visualization purposes. The dotted line in each panel is the initial gas surface density according to equation \ref{['eqn:surfaced_powerLaw']}.