The Anisotropy in Interstellar Media

• Applicant: Dr. Hua-bai Li
• Subject Area: Astrophysics and Astronomy
• Term: from 2011 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 203331259

Gravitational contraction, turbulence, and magnetic fields (B-fields) are generally accepted to be the key dynamical processes involved in interstellar media (ISM). How these processes interact with each other to form clouds, cores, and stars is, however, highly controversial. Many parameters that have been defined to describe these processes are isotropic (e.g., turbulent velocity, magnetic pressure, and virial equilibrium), but very recent observations have begun to reveal that density fragmentation and turbulent velocity in ISM may be highly filamentary. At the same time, Galactic B-fields have been found to be strong enough to imprint their orientations in many molecular clouds. These kinds of observations can place crucial constraints on competing ISM scenarios, because not all of them predict the observed anisotropy. Additional observations to increase the sample size are proposed here, along with new experiments designed for the forthcoming instruments and surveys.The challenge of understanding the ISM dynamics owes much to the lack of a practical method for measuring B-field strength. The novel method we proposed recently, based on the difference between ion and neutral turbulence, will be applied to filamentary density structures in molecular clouds. The method can simultaneously measure the energies of turbulence and B-fields, which will greatly help our understanding of the causes of ubiquitous cloud filaments.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1573: Physics of the Interstellar Medium