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Ground State Alignment- A promising Diagnostics of Astrophysical Magnetic Field


Speaker: Prof. Huirong Yan
Affiliation: Kavli Institute of Astronomy and Astrophysics, Peking University
Date: December 19, 2013 (Thu)
Time: 4:00 p.m.
Venue: Room 105, 1/F, Chong Yuet Ming Physics Building, HKU
Notice:Cancelled

Abstract

I would like to present a new technique of studying magnetic fields in interstellar and intergalactic gas/plasma we developed over the past few years. This technique is based on the alignment (in terms of their angular momentum in the ground state) of atoms and ions with fine or hyperfine splitting of the ground state. A unique feature of this technique is that the properties of the polarized radiation (both absorption and emission) depend on the 3D geometry of the magnetic field as well as the direction and anisotropy of incident radiation. I shall outline the prospects of the technique and its possible application to studies magnetic fields within circumstellar regions, interplanetary medium, interstellar medium, intergalactic medium. Both spatial and temporal variations of turbulent magnetic field can be traced with this technique as well. In addition, I shall demonstrate that atomic alignment induced by anisotropic radiation can cause polarization of the radio/far-infrared magnetic dipole transitions within the ground state, thus providing a possible way to study magnetic fields in environments where other techniques fail, e.g. at the epoch of Universe reionization.