anchoring magnetic fields in turbulent molecular clouds hua-bai li
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Anchoring Magnetic Fields
in Turbulent
Molecular Clouds
Hua-bai Li
~ 1
0 pc~
10
pc
Price & Bate 2008Price & Bate 2008
Girart et al. 2006Girart et al. 2006
300 AU300 AU
Flux Freezing: a feature of idea MHD
Burkhart et al.‘09
Sub- or Super- Alfvénic clouds ?Sub- or Super- Alfvénic clouds ?
Tang et al. 2009Tang et al. 2009
2 kAU
Hua-bai Li @ CC2YSO 2010
3
100 pc
The Background (BK) is IRAS 100 μm
optical1 pc
HertzLi et al. 2010 (in prep.)
Flux Freezing: a feature of idea MHDMulti-Scale Multi-Scale B-Field Observation of NGC B-Field Observation of NGC
6334 6334
Li et al. 2006
Hua-bai Li @ CC2YSO 2010
A
B
C
D
NGC 2071
NGC 2068
NGC 2024
IRAS 05327
E
F
G
H
OMC-3
OMC-2
OMC-1
OMC-4
0.3 pc
background: IRAS 100 μm
optical data (Heiles 2000)
Li et al. 2009
Optical vs. Submm polarimetryOptical vs. Submm polarimetry
Hua-bai Li @ CC2YSO 2010
Core Fields vs ICM Fields
Observations vs SimulationsObservations vs Simulations
Flux Freezing: a feature of idea MHDInside Cores vs. Inter CloudsInside Cores vs. Inter Clouds
Hua-bai Li @ CC2YSO 2010
Flux Freezing: a feature of idea MHD1. Anisotropic Gravitational Collapse1. Anisotropic Gravitational Collapse
Tassis et al. 2009
15 pc
0.6 pc0.1 pc
Li et al. 2010 (in prep.)Hua-bai Li @ CC2YSO 2010
Flux Freezing: a feature of idea MHD
0.6 pc
2. Turbulence Anisotropy2. Turbulence Anisotropy
Li et al. 2010 (in prep.)
Heyer et al. 2008
TMC
Av ~ 1
Hua-bai Li @ CC2YSO 2010
0.1 pc
Price & Bate 2008Price & Bate 2008
B
sim
ula
tion
Flux Freezing: a feature of idea MHD
0.6 pc
2. Turbulence Anisotropy2. Turbulence Anisotropy
Li et al. 2010 (in prep.)
Av > 7Av > 7
Hua-bai Li @ CC2YSO 2010
0.1 pc
Price & Bate 2008Price & Bate 2008
Av ~ 100Av ~ 100
B
sim
ula
tion 20
0”
300”
400”
500”
HCO+
0.1 pc
Flux Freezing: a feature of idea MHD
0.6 pc
3. Turbulent Ambipolar Diffusion3. Turbulent Ambipolar Diffusion
Li et al. 2010
Li & Houde 2008
Hua-bai Li @ CC2YSO 2010
ion
neu
tral
Houde et al. 2000
Tilley & Balsara 2010
sim
ula
tion
Ions and neutrals have different turbulent energyspectra in the AD scales
which givesdifferent linewidths
measured in the inertial range. This difference is
correlated with field strength
ion
neu
tral
HCO+
Flux Freezing: a feature of idea MHDSummary Summary
1. Clouds are sub-Alfvénic.
2. Local Galactic fields anchor in clouds down to cores ~ 0.1 pc, where B ~ 1mG, n(H2) ~ 10^6
3. The following consequences from dynamically important magnetic fields are observed in various densities:a. anisotropic gravitational collapseb. turbulent ambipolar diffusionc. turbulence anisotropy
Hua-bai Li @ CC2YSO 2010
random outflow direction
Curran & Chrysostomou 2007
initial/boundary conditions of cc2yso
initial/boundary conditions of cc2yso
Li, Hua-bai; Houde, Martin; Lai, Shih-ping; Sridharan, T. K., 2010, arXiv:1003.2919Li, Hua-bai; Dowell, C. Darren; Goodman, Alyssa; Hildebrand, Roger; Novak, Giles, 2009, ApJ,704, 891Curran, R. L.; Chrysostomou, A., 2007, MNRAS, 382, 699Price, D. & Bate, M., 2008, MNRAS, 385, 1820Dotson, J. et al., 2010, ApJS, 186, 406