SLIDE 1
Astrophysical Jets
Mirabel & Rodríguez (2002)
Mirabel & Rodríguez (1994) ~ 6,000 AU
There are a lot of them:
R.V.E. Lovelace HEPRO III, July 1, 2011
M87at2cmVLA Owenetal.1989,ApJ,340,698 - - PowerPoint PPT Presentation
M87at2cmVLA Owenetal.1989,ApJ,340,698 - - PowerPoint PPT Presentation
AstrophysicalJets R.V.E.LovelaceHEPROIII,July1,2011 Therearealotof them: ~ 6,000 AU Mirabel & Rodrguez (1994) Mirabel & Rodrguez (2002) M87at2cmVLA
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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
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Theoretical Models of Jets:
(a very concise summary)
Require large‐scale magnetic fields.
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Advection and compression of a weak field leads to a strong field in the inner disk. Bisnovatyi‐Kogan & Ruzmaikin 1976
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Lovelace(1975,1976) (a Poynting‐flux jet) Blandford (1976) Lovelace Nature
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Faraday disk dynamo
B E = - v B
r z
- /c
r r
1 2
v I E E
Btot
Lovelace 1975, 1976
accretion disk
SLIDE 8
B E = - v B
r z
- /c
r r
1 2
v
SLIDE 9
Kronberg, Lovelace, Lapenta, & Colgate, 2011, ApJL, in press
2kpc 7kpc
E3 E2 E1
First measurement of current flow in an extra‐galactic jet
arXiv:1106.1397
3C 303, z=0.14
SLIDE 10
Kronberg et al., 2011
Iz
SLIDE 11
From Kronberg et al. (2011): I_z = 3.*10^17 A
L_j =3.*10^36 W
________
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From Kronberg et al. (2011):
Benford, 1978, MNRAS, 183, 29 Nakamura, et al., 2008, ApJ, 686, 843
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I
AGN disk I return E3
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Advection/Diffusion of the B field:
Bisnovatyi‐Kogan & Ruzmaikin 1976
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- 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
But problems with this idea were discovered in the 1990’s
SLIDE 16
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)
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The Basic Idea
Advection in a nonturbulent surface layer
Accretion Velocity
SLIDE 18
Disk‐jet connection
(see also Tagger et al. 2004)
~ 20 min
Disk Signature of Jet Ejection
Observations of GRS 1915+105
(Eikenberry et al. 1998; Rothstein et al. 2005)
advected magnetic field jet turbulent disk timescales
SLIDE 19
z g(z) h
Bisnovatyi‐Kogan & Lovelace (2011)
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- 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.
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average(beta) =100
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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).
SLIDE 32
Conclusions Regarding Current Flow in kpc Jets (Kronberg et al. 2011):
- Poynting Flux Jet. Beta << 1.
- Axial current I ~ 1018 A.
- Jet Power = I2 Z with Z ~ 30 Ohms.
SLIDE 33
Ceiling of Gaudi’s Sagreda Familia Barcelona