Longitudinal Scales-Jets in Transition
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This meeting showed that three important transition scales along
jets are accessible to observation:
- A (few-parsec) scale of collimation and acceleration
(see Section 5.1)
- A (few-kiloparsec, galactic-core) scale of deceleration and
recollimation in FR I's (see Section 5.2)
- A (many-kiloparsec) scale of jet disruption and
bending in FR II's, which (see Norman,
these Proceedings) may correspond to that of
a self-actuated dentist's drill, entering the
"box of shocklets" it has created in the lobes. This
scale of bending and fraying of FR II jets into
filaments (Clarke, these Proceedings;
Hardee, these Proceedings) may be
quantifiable in Cygnus A (Carilli et al., these Proceedings)
and in some quasars (e.g.\
3C175, Bridle et al. 1994a).
3C353 (Swain, Bridle, & Baum, these Proceedings)
may be a case where one jet is presently within its
disruption scale and forms a hot spot, while the other is beyond it and
flails over the end of its lobe. Might a
high-velocity spine stabilize part of
a fraying relativistic jet as the boundary begins to disrupt?
And, if many hot spots are transient,
formed stochastically off-axis by fraying the jet boundaries, are the most
compact hot spots better tracers
of the beam paths? (In Cygnus A, the most
compact lobe features are closer to the initial jet direction
and to the longest axis of the lobe than are the brighter ``classical'' hot spots.)
Alan Bridle
Wed Apr 10 10:19:46 EDT 1996