All-Moscow Seminar of Astrophysicists
(ASA)
The seminar is supported by the grant of Federal Programm "Integration"
annotation of talk
Bisnovaty-Kogan G.S. (IKI)
"ADVECTIVE ACCRETION DISKS WITH MAGNETIC FIELDS AROUND BLACK HOLE"
Advection-dominated, accretion
flow onto a compact object,
recently considered by a number of authors,
assume that the dissipation of turbulent energy
of the flow heats the ions and
that the dissipated energy is advected inward.
It leads to efficiency of conversion
of accretion energy to radiation
very much smaller than unity.
However, when the flows have an equipartition magnetic
field a dissipation of magnetic
energy at a rate comparable to that for the
turbulence must occur by Ohmic heating.
We argue that this heating occurs as a
result of plasma instabilities and that the
relevant instabilities are current driven
in response to the strong electric fields
parallel to the magnetic field.
These instabilities heat
predominantly the electrons.
The conclusion is that the efficiency
of conversion of accretion energy to
radiation cannot be very small.
Some observational contaradictions to
ADAF model and reasons for existence of underluminous
AGN are discussed.