X-rays and Protoplanetary Disks

X-ray luminosities of T Tauri stars (TTS) and Class I protostars are commonly elevated by a thousand-fold above that of the present-day Sun. They undergo frequent powerful x-ray flares which can reach temperatures of similar to 100 MK, exposing the disk to intense bursts of ionizing radiation and high-energy particles. We provide a brief overview of how x-rays can affect protoplanetary disks and summarize x-ray diagnostics that can be used to infer disk properties. Representative x-ray observations of accreting young stellar objects with XMM-Newton and Chandra are discussed.