Impacts of Energetic Particles from T Tauri Flares on Inner Protoplanetary Discs

Abstract

T Tauri stars are known to be magnetically active stars subject to strong flares observed in X-rays. These flares are likely due to intense magnetic reconnection events during which a part of the stored magnetic energy is converted into kinetic energy of supra-thermal particles. Since T Tauri stars are surrounded by an accretion disc, these particles may influence the disc dynamics and chemistry. This work continues on a previous stationary model, which showed that energetic particles accelerated during flares can produce a strong ionisation rate at high column densities in the inner accretion disc. The present model includes non-stationary sequences of flaring events sampled by a Chandra X-ray survey of nearby young stellar objects. We calculate the averaged ionisation rate expected in a radius range from 0.08 to 0.6 au from the central star. We confirm that energetic particles produced by the flares dominate the ionisation of the disc up to column densities of $10^{25}~\rm{cm^{-2}}$. We further study the main consequences of this additional source of ionisation on the viscosity, the accretion rate, the volumetric heating rate and the chemical complexity of inner protoplanetary discs.