et al. 2003; Flaccomio et al. 2003a; Flaccomio, Micela & Sciortino 2003b; Stassun et al. 2004; Preibisch et al. 2005). Feigelson et al. (2003) find no correlation between rotation and X-ray activity and a “saturation level” of only $L_{\rm x}/L_{\rm
bol}\simeq 10^{-3.8}$ for pre-main-sequence (PMS) stars, both with and without discs, in the Orion Nebula Cluster (ONC). They suggest that a less efficient, turbulent “distributed” dynamo may act throughout the convective zones of these stars. On the other hand Flaccomio et al. (2003a,b) and Stassun et al. (2004) suggest that ONC stars with accretion discs bias the average $L_{\rm x}/L_{\rm bol}$ downwards, perhaps as a result of intrinsic absorption or changes in the magnetic field geometry. Preibisch et al. (2005) show that active accretion, rather than the mere presence of a disc is possibly responsible for the wider spread and lower median level of X-ray activity among the very young ONC stars.

NGC 2547 is an interesting open cluster in the context of studying the transition between the early behaviour of stellar coronae in star forming regions and the development of the well tested ARAP at older ages. It has a precisely determined age of either $30\pm5$Myr determined from fitting 