Studying the Local Magnetic Field and Anisotropy of Magnetic Turbulence by Synchrotron Polarization Derivative

• Published in: The Astrophysical journal Vol. 895; no. 1; pp. 20 - 29
• Main Authors: Zhang, Jian-Fu, Hu, Ke, Cho, Jungyeon, Lazarian, Alex
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.05.2020; IOP Publishing
• Subjects: Alfven waves; Anisotropy; Astrophysics; Computational fluid dynamics; Computer simulation; Correlation; Faraday effect; Fluid flow; Interplanetary turbulence; Interstellar plasma; Interstellar synchrotron emission; Magnetic fields; Magnetism; Magnetohydrodynamic turbulence; Magnetohydrodynamics; Numerical simulations; Polarization; Quadrupoles; Radiation; Spectral correlation; Statistical analysis; Turbulence
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab88ac

Due to the inevitable accumulation of observational information in the direction of the line of sight, it is difficult to measure the local magnetic field of magnetohydrodynamic (MHD) turbulence. However, a correct understanding of the local magnetic field is a prerequisite for reconstructing the Galactic 3D magnetic field. We study how to reveal the local magnetic field direction and the eddy anisotropy on the basis of the statistics of synchrotron polarization derivative with respect to the squared wavelength dP/dλ2. In the low-frequency and strong Faraday rotation regime, we implement numerical simulations in the combination of multiple statistic techniques, such as structure function, quadrupole ratio modulus, spectral correlation function, correlation function anisotropy, and spatial gradient techniques. We find that (1) statistic analysis of dP/dλ2 indeed reveals the anisotropy of underlying MHD turbulence, the degree of which increases with the increase of the radiation frequency; and (2) the synergy of both correlation function anisotropy and gradient calculation of dP/dλ2 enables the measurement of the local magnetic field direction.