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Recent high angular resolution ALMA observations have revealed numerous gaps in protoplanetary discs. A popular interpretation has been that planets open them. Most previous investigations of planet gap-opening have concentrated on viscous discs. Here, we carry out 2D (axisymmetric) global simulations of gap opening by a planet in a wind-launching non-ideal MHD disc with consistent thermochemistry. We find a strong concentration of poloidal magnetic flux in the planet-opened gap, where the gas dynamics are magnetically dominated. The magnetic field also drives a fast (nearly sonic) meridional gas circulation in the denser disc regions near the inner and outer edges of the gap, which may be observable through high-resolution molecular line observations. The gap is more ionized than its denser surrounding regions, with a better magnetic field–matter coupling. In particular, it has a much higher abundance of molecular ion HCO+, consistent with ALMA observations of the well-studied AS 209 protoplanetary disc that has prominent gaps and fast meridional motions reaching the local sound speed. Finally, we provide fitting formulae for the ambipolar and Ohmic diffusivities as a function of the disc local density, which can be used for future 3D simulations of planet gap-opening in non-ideal MHD discs where thermochemistry is too computationally expensive to evolve self-consistently with the magneto-hydrodynamics.

Observations of present-day mass-loss rates for close-in transiting exoplanets provide a crucial check on models of planetary evolution. One common approach is to model the planetary absorption signal during the transit in lines like Hei10830 with an isothermal Parker wind, but this leads to a degeneracy between the assumed outflow temperatureT₀and the mass-loss rate$\dot{M}$that can span orders of magnitude in$\dot{M}$. In this study, we re-examine the isothermal Parker wind model using an energy-limited framework. We show that in cases where photoionization is the only heat source, there is a physical upper limit to the efficiency parameterεcorresponding to the maximal amount of heating. This allows us to rule out a subset of winds with high temperatures and large mass-loss rates as they do not generate enough heat to remain self-consistent. To demonstrate the utility of this framework, we consider spectrally unresolved metastable helium observations of HAT-P-11b, WASP-69b, and HAT-P-18b. For the former two planets, we find that only relatively weak ($\dot{M}\lesssim {10}^{11.5}$g s⁻¹) outflows can match the metastable helium observations while remaining energetically self-consistent, while for HAT-P-18b all of the Parker wind models matching the helium data are self-consistent. Our results are in good agreement with more detailed self-consistent simulations and constraints from high-resolution transit spectra.