current models attempting to predict the chemistry, ionization state, heating, cooling, winds and dynamics of disks—processes thought to be at least partially controlled by X-rays—will need to be revised.

Being the first study of its kind, the TD09 work employed some simplifying assumptions. The most important of these in the context of the present work is that the EPs travel in straight lines. Solar energetic particles are known to follow the interplanetary (solar wind-borne) magnetic field to a large extent, though are able to traverse field lines in regions of significant MHD turbulence. Since T Tauri stars have strong surface magnetic fields and drive magnetized winds, their EPs will be expected to be trapped or deflected by the turbulent, magnetized T Tauri wind. The wind itself will also be deflected around the disk. @Feigelson.etal:02 note that the meteoritic isotopic anomalies present direct evidence that EPs do indeed impact the disk. However, it is quite uncertain what fraction of them, and under what acceleration circumstances and magnetic field characteristics, have trajectories favorable to disk penetration.

Given the potential importance of T Tauri EPs for disk ionization and chemistry, further study and assessment is warranted. Ionization and its effects on chemistry due 