Seminari
Thursday 24/10/2019 @ 14:30, INAF-OAS, sede del Battiferro, Seminar Room 4E10 (4th floor)
Alexandre Lazarian (University of Wisconsin - Madison), "Changing the Landscape: New Ways of Tracing and Probing Magnetic fields with Velocity and Synchrotron Gradients"
Modern understanding of MHD turbulence suggests that this type of turbulence is strongly anisotropic at small scales. Due to turbulent fast reconnection turbulent eddies are aligned with the magnetic field surrounding the eddies. This entails a conclusion that gradients of velocity and magnetic field are perpendicular to the local direction of the magnetic field. Guided by this fact we proposed, developed and successfully tested with observational data a set of new techniques for studying interstellar magnetic fields. I shall demonstrate how the velocity gradients can be measured using either velocity centroids of thin channel spectroscopic maps, while magnetic field gradients can be measured using synchrotron intensity or synchrotron polarization. I shall present 3D maps of galactic magnetic fields obtained with the new technique, demonstrate that gradients can provide both magnetic field tracing and identify the regions of gravitational collapse using observations of molecular clouds. I shall discuss new ways of obtaining magnetic field strength using the gradients. I shall show how to use different types of gradients to map the structure of the magnetic web within the multiphase interstellar media.