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We study the properties of powerful X-ray flares from 161 pre-main sequence(PMS) stars observed with the Chandra X-ray Observatory in the Orion Nebularegion. Relationships between flare properties, protoplanetary disks andaccretion are examined in detail to test models of star-disk interactions atthe inner edge of the accretion disks. Previous studies had found nodifferences in flaring between diskfree and accreting systems other than asmall overall diminution of X-ray luminosity in accreting systems. The mostimportant finding is that X-ray coronal extents in fast-rotating diskfree starscan significantly exceed the Keplerian corotation radius, whereas X-ray loopsizes in disky and accreting systems do not exceed the corotation radius. Thisis consistent with models of star-disk magnetic interaction where the innerdisk truncates and confines the PMS stellar magnetosphere. We also find twodifferences between flares in accreting and diskfree PMS stars. First, asubclass of super-hot flares with peak plasma temperatures exceeding 100 MK arepreferentially present in accreting systems. Second, we tentatively find thataccreting stars produce flares with shorter durations. Both results may beconsequences of the distortion and destabilization of the stellar magnetosphereby the interacting disk. Finally, we find no evidence that any flare types,even slow-rise flat-top flares are produced in star-disk magnetic loops. Allare consistent with enhanced solar long-duration events with both footprintsanchored in the stellar surface.

X-Ray flares in Orion Young Stars. II. Flares, Magnetospheres, and Protoplanetary Disks