We have re-analyzed using a hydrodynamic model large flaring events on three different categories of pre-main sequence (PMS) stars: the young stellar object (YSO) YLW15, the classical T Tauri star (CTTS) LkHα 92, the weak-line T Tauri star (WTTS) V773 Tau, and the WTTS HD 283572 (the first three objects were observed by ASCA, the last by ROSAT; all have been previously reported in the literatur...

The main subject of my talk is the question: in what kind of astrophysical systems magnetic reconnection is interesting and/or important? To address this question, I first put forward three general criteria for selecting the relevant astrophysical environments. Namely, reconnection should be: fast; energetically important; and observable. From this, I deduce that the gas density should be low, ...

We use a high-resolution cosmological simulation to predict the distribution of H I Lyα emission from the lowredshift (z . 0.5) intergalactic medium (IGM). Our simulation can be used to reliably compute the emission from optically thin regions of the IGM but not that of self-shielded gas. We therefore consider several models that bracket the expected emission from self-shielded regions. Most ga...