Some Consequences of Magnetic Fields in High Energy Sources

Magnetic fields likely play a fundamental intermediary role between gravity and radiation in many astrophysical rotators. They can, among other things, 1) induce and be amplified by turbulence, 2) energize coronae, 3) launch and collimate outflows in spring'' or fling’’ mechanisms. The first is widely recognized to be important for angular momentum transport, but can also produce intrinsic variability and possibly vorticity growth. The second leads to the production of high energy flares, and also facilitates a test of general relativity from AGN observations. The third can operate from rotators with a large scale fields, though the origin of the requisite large scale fields is somewhat unresolved. I discuss these three points in more detail below, emphasizing some open questions.