Although turbulence is chaotic, it can be described and understood. Turbulence is governed by well-defined statistical laws that can be studied and then successfully applied to solving astrophysical problems. In this project, Dr. Alexandre Lazarian (University of Wisconsin - Madison) seeks to advance theoretical understanding of magnetized turbulence in the interstellar medium (ISM) by both studying these laws and comparing theory with observations. These studies will build upon the existing research base and the enabling achievements obtained through Dr. Lazarian's earlier work that focused on the spectra of turbulence and its implications for cosmic rays. The present project is to address the role of small regions within the ISM turbulence in which the physical conditions are far from the average (called "intermittency"), as well as the feedback of cosmic rays to the compressible turbulence. In addition, this research will continue developing, testing, and applying new tools for extracting turbulence spectra from observations of the velocity profiles of spectral lines. As the result of this research, the observational community will have new tools to study turbulence and its anisotropy, as well as the topology of the ISM.
The appearance, evolution, and overall properties of a spiral galaxy are strongly influenced by its ISM. In turn, the nature of the ISM and many processes taking place within it (such as star-formation) are determined by the magnetic turbulence that stirs it. Examining magnetic turbulence at a fundamental level is vital to understanding many processes. Turbulence cannot be confidently understood using "brute force" numerical approaches only; the fluid motions simulated by computers differ from astrophysical ones by a huge difference in Reynolds numbers. In addition to the research that will be carried out under this project, Dr. Lazarian will mentor a graduate student as well as supervise REU and undergraduate student research projects. Dr. Lazarian will also carry out outreach activities, such as public lectures, and will make the statistical tools developed as a part of this project publicly available.
We live in turbulent world. Air in the atmosphere, water in rivers, even blood in our arteries is turbulent. Astrophysical plasmas is know to be turbulent as well. Turbulence changes properties of fluids dramatically. For instance, molecular diffusivity requires several months to spread sugar molecules in the cup of coffee. We never wait this long and employ turbulence by steering the coffee with a spoon. Similarly, calculations disregarding turbulence existing in the astrophysical systems may be meaningless. Turbulence is not just chaos, it is "ordered chaos". The order in turbulent flows can be revealed via statistical studies. Statistical descriptions filter out accidental features and focus on regular ones. Astrophysical fluids are magnetized with magnetic field playing crutial role for their dynamics. In this respect astrophysical turbulence is different from that we deal in our everyday life. Studies of such turbulence require skillful combining analytical, numerical and observational approaches. The research supported by the grant dealt with developing the theory of magnetic turbulence, numerical testing of the theory, developing techniques to study turbulence from observations, as well as studying astrophysical implications of turbulence. Substantial progress has been achieved in all the directions of research. For instance, a new theory of magnetic turbulence with spacially distributed sources and sinks of energy has been formulated and successfully tested numerically. In addition, new techniques of studying turbulence from observational data were developed and employed to get the properties of turbulence. Moreover, a new model of star formation appealing to the revealed properties of magnetic turbulence was proposed. The results were published in major astrophysical journals, including the Astrophysical Journal, Monthly Notices of Royal Astronomical Society, Nature etc.
