M87at2cmVLA Owenetal.1989,ApJ,340,698 - PowerPoint PPT Presentation

Astrophysical
Jets 
 R.V.E.
Lovelace




HEPRO
III,
July
1,
2011
 There
are
a
lot
of
 them:
 ~ 6,000 AU Mirabel & Rodríguez (1994) Mirabel & Rodríguez (2002)

M87
at
2cm
–VLA
 Owen
et
al.
1989,
ApJ,
340,
698

 Resolution
0.1".



 Field
of
View
10.00”
x
15.00”

 0.08
kpc


Theoretical 
Models
of
Jets: 
 (a
very
concise
summary)
 Require
large‐scale
 magnetic
fields.


Advection
and
 compression
of
a
 weak
field
leads
to
a
 strong
field
in
the
 inner
disk.
 Bisnovatyi‐Kogan
 &
Ruzmaikin
 1976


Lovelace(1975,1976)
 (a
Poynting‐flux
jet)
 Blandford
(1976)
 Lovelace
 Nature


� Faraday
disk
dynamo
 I B B tot E E accretion
 v � disk
 r r 2 1 /c E = - v B r z Lovelace
1975,
1976


� B v � r r 2 1 /c E = - v B r z

First

measurement
of
current
flow
in
an
extra‐galactic
jet
 Kronberg,
Lovelace,
Lapenta,
&
Colgate,
2011,
ApJL,
in
press
 arXiv:1106.1397
 7kpc
 2kpc
 E3
 E2
 E1
 3C
303,
z=0.14


Kronberg
et
al.,
2011
 I z

From
Kronberg
et
al.
(2011):
 I_z
=
3.*10^17
A
 L_j
=3.*10^36
W
 ________


From
Kronberg
et
al.
(2011):
 Benford,
1978,
 MNRAS,
183,
29
 Nakamura,
et
al.,
 2008,
ApJ,
686,
843


E3 I return I AGN disk

Advection/Diffusion
of
the
B
field:
 Bisnovatyi‐Kogan
 &
Ruzmaikin
 1976


But
problems
with
this
idea
 were
discovered
in
the
1990’s
 • Turbulence
responsible
for
accretion
 also
leads
to
enhanced
reconnection
 (field
diffusivity)
 • A
turbulent
disk
is
a
poor
conductor
 • Weak
fields
do
not
advect
inward
in
a
 thin
disk
 disk

How
might
weak
magnetic
fields
be
 able
to
advect?
inward 
 • Could
be
achieved
with
a
mathematically
favorable
vertical
 profile
of
the
diffusivity
(Ogilvie
&
Livio
2001)
 • Physical
model:
 Assuming 
the
surface
layer
of
the
disk
is
 nonturbulent
(i.e.,
highly
conducting),
it
can
support
inward
 field
advection:
 Bisnovatyi-Kogan & Lovelace (2011); Lovelace, Rothstein, & Bisnovatyi-Kogan (2009,ApJ);Rothstein &Lovelace(2008,ApJ);Bisnovatyi- Kogan & Lovelace (2007, ApJ)

The
Basic
Idea
 Advection
in
a
nonturbulent
surface
layer
 Accretion Velocity

Disk‐jet
connection
 advected magnetic field Signature of Jet Ejection Disk turbulent disk jet timescales ~ 20 min 
 Observations of GRS 1915+105 (see
also
Tagger
et
al.
2004)
 (Eikenberry et al. 1998; Rothstein et al. 2005)

Bisnovatyi‐Kogan
&
Lovelace
(2011)
 g(z)
 z
 h


 
Parameters:

three
coefficients
of
solution;
 alpha=viscosity;
epsilon=h/r;
and
beta.

  
Need
to
vary
beta
in
order
to
satisfy
all
of
 the
boundary
conditions.


average(beta)
=100


Conclusions
Regarding
Advection/ Diffusion
of
B
Field
 • There
is
a
critical
value
of
beta
for
 stationary
conditions
of
an
accretion

 disk
threaded
by
a
poloidal
magnetic
 field. 
 • It
is
approximately
beta
=240
for
a
 turbulent
Prandtl
#
=
1,
alpha
=
0.1,
and
 



h/r
=
0.05.
 • .

For
smaller
beta
the
field
advects
 inward
whereas
for
larger
beta
the
field
 diffuses
outward
(Bisnovatyi‐Kogan
and
 Lovelace
2011). 


Conclusions
Regarding
Current
 Flow
in
kpc
Jets
(Kronberg
et
al.
2011):
 • Poynting
Flux
Jet.

Beta
<<
1.
 • Axial
current
I
~
10 18 
A.
 • Jet
Power
=
I 2 
Z

with
Z
~
30
Ohms.


Ceiling
of
Gaudi’s
Sagreda
Familia
Barcelona