Institute for Advanced Study / Princeton University Joint Astrophysics Colloquium

Abstract: In extreme astrophysical systems, such as black hole coronae and pulsar magnetospheres, the process of magnetic reconnection is significantly modified by strong radiative cooling. This cooling removes internal energy faster than it is injected by the reconnection process, triggering a radiative collapse in which runaway cooling and compression leads to a cold, thin, and dense reconnection layer. The high-energy X-ray radiation released is, in turn, often the only signature of reconnection in these remote astrophysical environments. To study this process, we have conducted a series of radiatively cooled reconnection experiments driven by the Z Machine at Sandia National Laboratories, the world's largest pulsed-power facility. I will present observations of the formation of brightly-emitting and fast-moving hotspots within the reconnection layer, which we interpret as plasmoids formed by the tearing instability. These hotspots emit the majority of the high energy X-rays, localising the radiation signature in space and time.