1. Anchoring Magnetic Fields in Turbulent Molecular Clouds Hua-bai Li

2. ~ 10 pc Price & Bate 2008 Girart et al. 2006 300 AU Flux Freezing : a feature of idea MHD Burkhart et al. ‘09 Sub- or Super- Alfvénic clouds ? Tang et al. 2009 2 kAU Hua-bai Li @ CC2YSO 2010

3. 3 100 pc The Background (BK) is IRAS 100  m optical 1 pc Hertz Li et al. 2010 (in prep.) Flux Freezing : a feature of idea MHD Multi-Scale B-Field Observation of NGC 6334 Li et al. 2006 Hua-bai Li @ CC2YSO 2010

4. ABCDABCD 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  m optical data (Heiles 2000) Li et al. 2009 Optical vs. Submm polarimetry Hua-bai Li @ CC2YSO 2010

5. Core Fields vs ICM Fields Observations vs Simulations Flux Freezing : a feature of idea MHD Inside Cores vs. Inter Clouds Hua-bai Li @ CC2YSO 2010

6. Flux Freezing : a feature of idea MHD 1. 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

7. Flux Freezing : a feature of idea MHD 0.6 pc 2. 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 2008 B simulation

8. Flux Freezing : a feature of idea MHD 0.6 pc 2. Turbulence Anisotropy Li et al. 2010 (in prep.) Av > 7 Hua-bai Li @ CC2YSO 2010 0.1 pc Price & Bate 2008 Av ~ 100 B simulation 200” 300” 400”500” HCO+

9. 0.1 pc Flux Freezing : a feature of idea MHD 0.6 pc 3. Turbulent Ambipolar Diffusion Li et al. 2010 Li & Houde 2008 Hua-bai Li @ CC2YSO 2010 ion neutral Houde et al. 2000 Tilley & Balsara 2010 simulation Ions and neutrals have different turbulent energy spectra in the AD scales which gives different linewidths measured in the inertial range. This difference is correlated with field strength ion neutral HCO+

10. Flux Freezing : a feature of idea MHD Summary 1. Clouds are sub-Alfvénic. 2. Local Galactic fields anchor in clouds down to cores ~ 0.1 pc, where B ~ 1mG, n(H 2 ) ~ 10^6 3. The following consequences from dynamically important magnetic fields are observed in various densities: a. anisotropic gravitational collapse b. turbulent ambipolar diffusion c. turbulence anisotropy Hua-bai Li @ CC2YSO 2010 random outflow direction Curran & Chrysostomou 2007 initial/boundary conditions of cc2yso

11. Li, Hua-bai; Houde, Martin; Lai, Shih-ping; Sridharan, T. K., 2010, arXiv:1003.2919 Li, Hua-bai; Dowell, C. Darren; Goodman, Alyssa; Hildebrand, Roger; Novak, Giles, 2009, ApJ, 704, 891 Curran, R. L.; Chrysostomou, A., 2007, MNRAS, 382, 699 Price, D. & Bate, M., 2008, MNRAS, 385, 1820 Dotson, J. et al., 2010, ApJS, 186, 406