Black-Hole Accretion Disks and Stellar Coronae: A Physical Analogy

X-ray and radio observations have the potential of revealing the physics of gas just before it falls into black holes. However, the details of black hole accretion remain obscured, and in particular the origin of their radio emission is contentious. Stellar coronae, like that of our Sun, are also known to be X-ray and radio sources, and are much better understood. Despite the vast disparity in size and mass, there is evidence that micro-physical processes are similar in both sources. The talk will thus explain how we can learn about black hole accretion by analogy with stellar coronae. We will also describe the many difficulties in this analogy, and how those are confronted with new observations. Especially observations in the mm band (~100 GHz) are shedding new light on the nature of black-hole accretion-disk coronae.