**title** Asp Conference Series, Vol. **volume***, **year of Publication** **names of Editors** Microquasars as Sources of High Energy Phenomena

Relativistic outflows are a common phenomenon in accreting black holes. Despite the enormous differences in scale, accreting stellar-mass black holes (X-ray binaries, collapsars) and super-massive black holes produce jets with analogous physical properties. Here I review microquasars as sources of relativistic jets, gamma-rays, cosmic rays, and high energy neutrinos. 1. The quasar-microquasar analogy Microquasars are scaled-down versions of quasars and both are believed to be powered by spinning black holes with masses of up to a few tens that of the Sun (see Figure 1). The word microquasar was chosen by Mirabel et al. (1992) to suggest that we could learn about microquasars from previous decades of studies on AGN. In fact, the analogy with quasars is more than morphological, because there is an underlying unity in the physics of accreting black holes over an enormous range of scales, from stellar-mass black holes in binary stellar systems, to super-massive black holes at the centre of distant galaxies (Rees, 1998). A major difference is that the linear and time scales of the phenomena are proportional to the black hole mass. In quasars and microquasars are found the following three basic ingredients: 1) a spinning black hole, 2) an accretion disk heated by viscous dissipation, and 3) collimated jets of relativistic particles. However, in microquasars the black hole is only a few solar masses instead of several million solar masses; the accretion disk has mean thermal temperatures of several million degrees instead of several thousand degrees; and the particles ejected at relativistic speeds can travel up to distances of a few light-years only, instead of the several million light-years as in some giant radio galaxies. In quasars matter can be drawn into the accretion disk from disrupted stars or from the interstellar medium of the host galaxy, whereas in microquasars the material is being drawn from the companion star in the binary system. In quasars the accretion disk has sizes of ∼10 9 km and radiates mostly in the ultraviolet and optical wavelengths, whereas in microquasars the accretion disk has sizes of ∼10 3 km and the bulk of the radiated energy comes out in the X-rays. It is believed that part of the spin energy of the black hole can be tapped to power the collimated ejection of magnetized plasma at relativistic speeds.