New diagnostics of astrophysical magnetic field based on atomic alignment
Huirong Yan
Postdoctoral Fellow Canadian Institute for Theoretical Astrophysics

I shall present a new technique of studying magnetic fields in diffuse astrophysical media, e.g. interstellar and intergalactic gas/plasma. This technique is based on the angular momentum alignment of atoms and ions in their ground or metastable states. As their life-time in such states is long, the alignment induced by anisotropic radiation is susceptible to weak magnetic fields in diffuse medium. The alignment reveals itself in terms of the polarization of the absorbed and emitted light. A variety of atomic species with fine or hyperfine splitting of the ground or metastable states exhibit the alignment and the resulting polarization degree in some cases exceeds 20 %. A unique feature of these studies is that they can reveal the 3D orientation of magnetic field.

In addition, I shall demonstrate that the polarization of the far IR or radio radiation arising from the transitions between fine and hyperfine states of the ground level can provide yet another promising diagnostics of magnetic fields, including the magnetic fields in the Early Universe. I shall outline several cases of interplanetary, circumstellar and interstellar magnetic fields for which the studies of magnetic fields using ground state atomic alignment effect are promising.

Date:	Jeudi, 4 septembre 2008
Time:	12:30
Where:	Université de Montréal
	Pavillon Roger-Gaudry, Local D-460
Contact:	Pierre Bergeron