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IMPLOSIVE
ACCRETION AND OUTBURSTS OF ACTIVE GALACTIC NUCLEI
Authors:
R.V.E. Lovelace, M.M. Romanova, and W.I. Newman
A model and simulation code have been developed for time-dependent
axisymmetric disk accretion onto a compact object including for the first time the
influence of an ordered magnetic field. The accretion rate and radiative luminosity of the
disk are naturally coupled to the rate of outflow of energy and angular momentum in
magnetically driven ± z winds. The magnetic field of the wind is treated in a phenomenological way suggested by
self-consistent wind solutions. The radial accretion speed u(r,t) of the disk matter is
shown to be the sum of the usual viscous contribution and a magnetic contribution
µ r2/3 Bp2 / s
where Bp (r,t) is the poloidal field threading the disk and s (r,t) is the disk's surface mass
density. An enhancement or variation in Bp
at a large radial distance leads to the formation of a soliton-like structure
in the disk density, temperature, and B-field which propagates implosively
inward. The
implosion gives a burst in the power output in winds or jets and a simultaneous burst in
the disk radiation. The model is pertinent to the formation of discrete fast moving
components in jets observed by very - long - baseline interferometry. These components
appear to originate at times of optical outbursts of the active galactic nucleus.
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