Impact of embedded circumplanetary winds on the circumstellar disk: I. Reshaping the local accretion environment

The existence of winds is among the uncertainties related to the growth of giant planets. Such circumplanetary outflows have been proposed to explain kinematic and chemical structures in protoplanetary disks. We investigate the immediate impact of circumplanetary outflows on the circumstellar disk environment, the planetary vicinity, and planetary growth. We performed three-dimensional hydrodynamic simulations using \texttt{FARGO3D}, implementing a parametric wind launched from the vicinity of an embedded planet. Although the imposed configurations for the outflows do not significantly alter the global structure of the disk, they do substantially redistribute material in the vicinity of the embedded planet. In particular, the wind redirects accretion flows from polar to equatorial latitudes, resulting in variable accretion patterns over time. Although the mass accretion rate variations depend on the efficiency of the outflows, their presence diminishes the accretion rate over time and the total mass reservoir within the Hill sphere and the planet’s direct vicinity, potentially slowing or limiting planetary growth.

💡 Research Summary

The authors investigate how localized outflows from an embedded giant planet—so‑called circumplanetary winds—affect the surrounding protoplanetary disk and the planet’s own accretion environment. Rather than modeling a specific launching mechanism (e.g., magneto‑centrifugal or thermally driven winds), they introduce a parametric wind acceleration term into three‑dimensional hydrodynamic simulations performed with the public FARGO3D code. The wind is prescribed as a bipolar, radially outward acceleration Γ(r′,θ′)=Aγ (GM★/R0²) exp(−r′²/rs²) cosⁿθ′ êr′, where r′ is the distance from the planet, rs≈rH/2 (half the Hill radius) sets the spatial scale, n=8 controls collimation, and Aγ determines the strength. The acceleration is switched off beyond rs, ensuring the wind acts only within the planet’s immediate Hill sphere.

The disk model is a locally isothermal, viscous (α=10⁻⁴) gas disk around a solar‑mass star, with the planet on a fixed circular orbit at 10 AU. The numerical grid (φ=768, r=364, θ=144) resolves the Hill sphere with ~11 cells radially and ~5 cells across the wind injection region, allowing a faithful capture of the wind‑disk interaction. Simulations are run for 500 planetary orbits, long enough for a quasi‑steady state to develop after the abrupt introduction of the planetary potential.

Key findings are: (1) In the control runs without a wind, gas flows from high latitudes into the Hill sphere and then down to the midplane, reproducing the classic polar‑to‑equatorial accretion pattern seen in previous 3‑D studies. (2) When the wind is active, this pattern is dramatically altered. The wind redirects the polar inflow upward and outward, funneling material toward the equatorial region. This re‑distribution reduces the density inside the Hill sphere, especially within 0.2 rH of the planet, where the mass reservoir can drop by more than 50 % for strong winds (Aγ≈1). (3) The planetary mass accretion rate declines by 30–50 % relative to the wind‑free case, with larger reductions for higher Aγ. Weak winds produce strong temporal variability in the accretion rate, but the long‑term average remains lower. (4) Because the wind is confined to r′≤rH/2, the global disk structure (spiral wakes, surface density profile) is essentially unchanged; the wind’s influence is strictly local.

The authors interpret these results as evidence that circumplanetary winds can act as a feedback mechanism that throttles planetary growth. By evacuating gas from the Hill sphere and reshaping the inflow geometry, the wind reduces the net mass flux onto the planet. They also note that the induced velocity perturbations (a fraction f of the local Keplerian speed) could generate subtle Doppler‑flip signatures observable with high‑resolution ALMA or JWST spectroscopy, offering a potential avenue for indirect detection of such winds. Finally, the parametric approach provides a flexible framework to explore a wide range of wind strengths and geometries, paving the way for future studies that couple this method with more realistic MHD or radiative‑hydrodynamic wind launching models.