  In this Letter we use a simple model to demonstrate the observational
signatures of the magnetic connection between a black hole and a disk: (1) With
the magnetic connection more energy is dissipated in and radiated away from
regions close to the center of the disk; (2) The magnetic connection can
produce a very steep emissivity compared to the standard accretion; (3) The
observational spectral signature of the magnetic connection can be robust.
These signatures may be identified with the observations of Chandra and
XMM-Newton. In fact, the steep emissivity index for the Seyfert 1 galaxy
MCG--6-30-15 inferred from the recent XMM-Newton observation is very difficult
to be explained with a standard accretion disk but can be easily explained with
the magnetic connection between a black hole and a disk.
