External Photoevaporation of the Solar Nebula II: Effects on Disk Structure and Evolution with Non-Uniform Turbulent Viscosity due to the Magnetorotational Instability

Abstract

The structure and evolution of protoplanetary disks, especially the radial flows of gas through them, are sensitive to a number of factors. One that has been considered only occasionally in the literature is external photoevaporation by far-ultraviolet (FUV) radiation from nearby, massive stars, despite the fact that nearly half of all disks will experience photoevaporation. Another effect apparently not considered in the literature is a spatially and temporally varying value of $\alpha$ in the disk [where the turbulent viscosity $\nu$ is $\alpha$ times the sound speed C times the disk scale height H]. Here we use the formulation of Bai \& Stone (2011) to relate $\alpha$ to the ionization fraction in the disk, assuming turbulent transport of angular momentum is due to the magnetorotational instability. We find that disk evolution is most sensitive to the surface area of dust. Typically $\alpha \lesssim 10^{-5}$ in the inner disk ($<2$ AU), rising to $\sim 10^{-1}$ beyond 20 AU. This drastically alters the structure of the disk and the flow of mass through it: while the outer disk rapidly viscously spreads, the inner disk hardly evolves; this leads to a steep surface density profile with a slope < p > $\approx$ 2 - 5 in the 5-30 AU region) that is made steeper by external photoevaporation. We also find that the combination of variable $\alpha$ and external photoevaporation eventually causes gas as close as 3 AU, previously accreting inward, to be drawn outward to the photoevaporated outer edge of the disk. These effects have drastic consequences for planet formation and volatile transport in protoplanetary disks.

65 pages, 23 figures, Accepted for publication in the Astrophysical Journal

References in corpus (9)

• Protoplanetary Disk Structures in Ophiuchus
• Constraining the X-ray and Cosmic Ray Ionization Chemistry of the TW Hya Protoplanetary Disk: Evidence for a Sub-interstellar Cosmic Ray Rate
• No universal minimum-mass extrasolar nebula: Evidence against in-situ accretion of systems of hot super-Earths
• ALMA Observations of the Orion Proplyds
• Massive planet migration: Theoretical predictions and comparison with observations
• Exclusion of Cosmic Rays in Protoplanetary Disks. II. Chemical Gradients and Observational Signatures
• External Photoevaporation of the Solar Nebula: Jupiter's Noble Gas Enrichments
• Simulating planet migration in globally evolving disks
• The Phases of Water Ice in the Solar Nebula

Cited by in corpus (10)

• The Effect of Jupiter's Formation on the Distribution of Refractory Elements and Inclusions in Meteorites
• The FRIED grid of mass loss rates for externally irradiated protoplanetary discs
• Constraints from Dust Mass and Mass Accretion Rate Measurements on Angular Momentum Transport in Protoplanetary Disks
• Where can a Trappist-1 planetary system be produced?
• Rocklines as Cradles for Refractory Solids in the Protosolar Nebula
• Formulas for Radial Transport in Protoplanetary Disks
• A Herschel view of protoplanetary disks in the $\sigma$ Ori cluster
• Disk evolution and the fate of water
• Effect of Different Angular Momentum Transport mechanisms on the Distribution of Water in Protoplanetary Disks
• Linking Outer Disk Pebble Dynamics and Gaps to Inner Disk Water Enrichment