Cool Stars 14 - Submitted Abstract # 97 This version created on 05 October 2006 DROXO: X-ray Flares and Coronal Structures in Rho Ophiuchi Ettore Flaccomio, INAF - OAPA Beate Stelzer, INAF - OAPA Ignazio Pillitteri, INAF - OAPA Giusi Micela, INAF - OAPA Fabio Reale, INAF - OAPA Salvo Sciortino, INAF - OAPA We present time resolved spectroscopy of bright X-ray flares from young PMS stars observed during the Deep Rho Ophiuchi XMM-Newton Observation (DROXO). Because of its long exposure time, 450 Ks, DROXO is so far the best dataset for the study of X-ray time variability in the Rho Oph ~1 Myr stellar population and of their flares in particular. We interpret the observed time-evolution of the plasma temperatures and emission measures by assuming that X-rays are emitted by plasma confined in magnetic loops and subject to both impulsive and sustained heating. We thus estimate the length of the magnetic loops, the minimum strength of the confining magnetic fields and the densities of the flaring plasma. We finally compare our results for the very young Rho Ophiuchi YSOs with similar ones obtained, with the same method, for more evolved young stars, e.g. in the Orion Nebula Cluster (1-2 Myr) and in the Upper Scorpius association (~5 Myr). ----------------------------------