its dynamics and the nature of any planetary system that forms within it.

In either a disk wind or MRI dominated regime it now appears that cosmic ray ionization and driving of accretion runs into difficulties because they can be effectively shielded from the disk by the magnetized T Tauri wind [@Cleeves.etal:13; @Drake.etal:17]. Even in the absence of significant cosmic ray shielding, Glassgold and co-workers [e.g. @Glassgold.etal:97; @Igea.Glassgold:99] realised that X-ray emission from the corona of a disk-hosting T Tauri star will likely dominate the gas ionization in the zones of planet formation, out to 50 AU or more. The penetrating power of X-rays provides ionization in deeper disk layers than can be reached by UV and EUV photons. Ionization by the central star is also pivotal for disk chemistry in intermediate and surface layers [e.g. @Aikawa.Herbst:99; @Semenov.etal:04; @Walsh.etal:12] and could additionally be responsible for alteration of the structure of dust grains [e.g. @Glauser.etal:09; @Ciaravella.etal:16].

While X-ray emission is now accepted as a major ionization source and angular momentum transport driver, @Turner.Drake:09, hereafter TD09, suggested that flare energetic particles—analogous to solar energetic particles (EPs) accelerated during large solar flares—can contribute significantly to disk ionization. The basis for the TD09 result 