Tracing Magnetic Fields with Ground State Alignment
arXiv:1203.5571 · doi:10.1016/j.jqsrt.2012.03.027
Abstract
Observational studies of magnetic fields are vital as magnetic fields play a crucial role in various astrophysical processes, including star formation, accretion of matter, transport processes (e.g., transport of heat), and cosmic rays. We identified a process "ground state alignment" as a new way to determine the magnetic field direction in diffuse medium. The alignment is due to anisotropic radiation impinging on the atom/ion, while the magnetic field induces precession and realign the atom/ion and therefore the polarization of the emitted or absorbed radiation reflects the direction of the magnetic field. The atoms get aligned at their low levels and, as the life-time of the atoms/ions we deal with is long, the alignment induced by anisotropic radiation is susceptible to weak magnetic fields (G). Compared to the upper level Hanle effect, atomic realignment is most suitable for the studies of magnetic field in the diffuse medium, where magnetic field is relatively weak. In fact, the effects of atomic/ionic alignment, including the realignment in magnetic field, were studied in the laboratory decades ago, mostly in relation to the maser research. Recently, the atomic effect has been already detected in observations from circumstellar medium and this is a harbinger of future extensive magnetic field studies. A unique feature of the atomic realignment is that they can reveal the 3D orientation of magnetic field. In this article, we shall review the basic physical processes involved in atomic realignment and its applications to interplanetary, circumstellar and interstellar magnetic fields. In addition, our research reveals that the polarization of the radiation arising from the transitions between fine and hyperfine states of the ground level can provide a unique diagnostics of magnetic fields, including those in the Early Universe.
42 pages, 11 figures, invited review, JQSRT in press, typos corrected
References in corpus (16)
- Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
- Radiative torques: Analytical Model and Basic Properties
- Tracing Magnetic Fields with Aligned Grains
- Studies of regular and random magnetic fields in the ISM: statistics of polarization vectors and the Chandrasekhar-Fermi technique
- Radiative torque alignment: Essential Physical Processes
- Velocity centroids as tracers of the turbulent velocity statistics
- Statistical Description of Synchrotron Intensity Fluctuations: Studies of Astrophysical Magnetic Turbulence
- Radiative torques alignment in the presence of pinwheel torques
- Alignment of Dust with Magnetic Inclusions: Radiative Torques and Superparamagnetic Barnett and Nuclear Relaxation
- Velocity Anisotropy as a Diagnostic of the Magnetization of the Interstellar Medium and Molecular clouds
- Polarization of absorption lines as a diagnostics of circumstellar, interstellar and intergalactic magnetic fields: Fine structure atoms
- Atomic alignment and Diagnostics of Magnetic Fields in Diffuse Media
- Polarization from aligned atoms as a diagnostics of circumstellar, AGN and interstellar magnetic fields: II. Atoms with Hyperfine Structure
- Cosmic Magnetic Fields: Observations and Prospects
- A New Mechanism for Polarizing Light from Obscured Stars
- Ground-state alignment of atoms and ions: New Diagnostics of Astrophysical Magnetic field in diffuse medium
Cited by in corpus (18)
- Grain Alignment by Radiative Torques in Special Conditions and Implications
- Magnetic Properties of Dust Grains, Effect of Precession and Radiative Torque Alignment
- Magnetic field strength from turbulence theory (I): Using differential measure approach (DMA)
- Anisotropic Turbulence in Position-Position-Velocity Space: Probing Three-Dimensional Magnetic Fields
- The Polstar High Resolution Spectropolarimetry MIDEX Mission
- New probe of magnetic fields in the prereionization epoch. I. Formalism
- Diagnosis of 3D magnetic field and modes composition in MHD turbulence with Y-parameter
- Three-dimensional magnetic fields of molecular clouds
- A new probe of magnetic fields in the pre-reionization epoch: II. Detectability
- Discovery of polarizations from ground state absorption lines: tracer of sub-Gauss magnetic field on 89Her
- Polarisation of submillimetre lines from interstellar medium
- Ultraviolet Spectropolarimetry with Polstar: Interstellar Medium Science
- Tracing Magnetic Fields by Atomic Alignment in Extended Radiation Fields
- Magnetic field measurement from the Davis-Chandrasekhar-Fermi method employed with Atomic Alignment
- Exploring the environment, magnetic fields, and feedback effects of massive high-redshift galaxies with [CII]
- The influence of atomic alignment on absorption and emission spectroscopy
- Diagnosing Interstellar Magnetic Turbulence with TeV Pulsar Halos
- The science case for POLLUX, a high-resolution UV spectropolarimeter onboard LUVOIR