  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, so that the plasma is: collisionless; force-free; and optically thin.
Thus, for example, the requirement that reconnection is fast implies that
Petschek's reconnection mechanism must be operating, which is possible,
apparently, only in the collisionless regime. Next, I argue that the force-free
condition implies that the magnetic field be produced in, and anchored by, a
nearby dense massive object, e.g., a star or a disk, strongly stratified by
gravity. I then stress the importance of field-line opening (e.g., by
differential rotation) as a means to form a reconnecting current sheet.
Correspondingly, I suggest the Y-point helmet streamer as a generic
prototypical magnetic configuration relevant to large-scale reconnection in
astrophysics. Finally, I discuss several specific astrophysical systems where
the above criteria are met: stellar coronae, magnetically-interacting
star--disk systems, and magnetized coronae above turbulent accretion disks. In
the Appendix, I apply the ideas put forward in this talk to the solar coronal
heating problem.
