Unveiling the Nature of Coronae in Active Galactic Nuclei through Sub-mm
  Observations
  The heating mechanism of a corona above an accretion disk in active galactic
nuclei (AGNs) is still unknown. One possible mechanism is magnetic reconnection
heating requiring energy equipartition between magnetic energy and gas energy
in the disk. Here, we investigate the expected observed properties in radio
band from such a magnetized corona. A magnetized corona can generate
synchrotron radiation since a huge amount of electrons exists. Although most of
radiation would be absorbed by synchrotron self-absorption, high-frequency end
of synchrotron emission can escape from a corona and appears at the sub-mm
range. If only thermal electrons exist in a corona, the expected flux from
nearby Seyferts is below the Atacama Large Millimeter/ submillimeter Array
(ALMA) sensitivity. However, if non-thermal electrons coexist in a corona, ALMA
can measure the non-thermal tail of the synchrotron radiation from a corona.
Such non-thermal population is naturally expected to exist if the corona is
heated by magnetic reconnections. Future ALMA observations will directly probe
the coronal magnetic field strength and the existence of non-thermal electrons
in coronae of AGNs.
