Mottled Protoplanetary Disk Ionization by Magnetically Channeled T Tauri Star Energetic Particles
AffiliationUniv Arizona, Dept Astron
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PublisherIOP PUBLISHING LTD
CitationMottled Protoplanetary Disk Ionization by Magnetically Channeled T Tauri Star Energetic Particles 2018, 853 (2):112 The Astrophysical Journal
JournalThe Astrophysical Journal
Rights© 2018. The American Astronomical Society. All rights reserved.
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AbstractThe evolution of protoplanetary disks is believed to be driven largely by angular momentum transport resulting from magnetized disk winds and turbulent viscosity. The ionization of the disk that is essential for these processes has been thought to be due to host star coronal X-rays but could also arise from energetic particles produced by coronal flares, or traveling shock waves, and advected by the stellar wind. We have performed test-particle numerical simulations of energetic protons propagating into a realistic T. Tauri stellar wind, including a superposed small-scale magnetostatic turbulence. The isotropic (Kolmogorov power spectrum) turbulent component is synthesized along the individual particle trajectories. We have investigated the energy range [0.1-10] GeV, consistent with expectations from Chandra X-ray observations of large flares on T. Tauri stars and recent indications by the Herschel Space Observatory of a significant contribution of energetic particles to the disk ionization of young stars. In contrast with a previous theoretical study finding a dominance of energetic particles over X-rays in the ionization throughout the disk, we find that the disk ionization is likely dominated by X-rays over much of its area, except within narrow regions where particles are channeled onto the disk by the strongly tangled and turbulent magnetic field. The radial thickness of such regions is 5 stellar radii close to the star and broadens with increasing radial distance. This likely continues out to large distances from the star (10 au or greater), where particles can be copiously advected and diffused by the turbulent wind.
VersionFinal published version
SponsorsNational Aeronautics and Space Administration through Chandra Award [TM6-17001B]; National Aeronautics and Space Administration [NAS8-03060]; NASA [NAS8-03060, NNX15AJ71G]; NASA LWS grant [NNX16AC11G]; NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center