Event DetailsEvent Dates: Wednesday, August 13, 2014 - 12:00pmSeminar Location: CASA Conference Room C324Speaker Name(s): Marek SikoraSpeaker Affiliation(s): Nicolaus Copernicus Astronomical Center Seminar Type/SubjectScientific Seminar Type: Astrophysics Lunch SeminarEvent Details & Abstract: Magnetic fluxes required to power jets in radio-loud quasars are significantly greater than those that can develop in standard accretion disks. The required levels of those fields are achievable only by the accumulation process, which proceeds via advection of magnetic fields by the accreting matter. Eventually, this leads to the formation of a magnetosphere over the black hole and the innermost portions of the accretion flow. Since the advection of magnetic fields is expected not to work efficiently in geometrically thin disks, we suggest that such an accumulation of magnetic flux occurs via hot, quasi-spherical accretion. Without this pre-phase, the cold accretion events are expected to result in radio quiet (or at most, moderately radio-loud) quasars.