Search

Since synchrotron polarization fluctuations are related to the fundamental properties of the magnetic field, we propose the polarization intensity variance to measure the Galactic interstellar medium (ISM) magnetization. We confirm the method's applicability by comparing it with the polarization angle dispersion and its reliability by measuring the underlying Alfvénic Mach number of magnetohydrodynamic turbulence. With the finding of the power-law relation of A ∝ M A 2 between polarization intensity variance A and Alfvénic Mach number M A, we apply the new technique to the Canadian Galactic Plane Survey data, achieving the Alfvénic Mach number of the Galactic ISM. Our results show that the low-latitude Galactic ISM is dominated by sub-Alfénic turbulence, with M A approximately between 0.5 and 1.0. [ABSTRACT FROM AUTHOR]

This paper employs an MHD-PIC method to perform numerical simulations of magnetic-reconnection-driven turbulence and turbulent reconnection acceleration of particles. Focusing on the dynamics of the magnetic reconnection, the properties of self-driven turbulence, and the behavior of particle acceleration, we find the following: (1) When reaching a statistically steady state of the self-driven turbulence, the magnetic energy is almost released by 50%, while the kinetic energy of the fluid increases by no more than 15%. (2) The properties of reconnection-driven turbulence are more complex than the traditional turbulence driven by an external force. (3) The strong magnetic field tends to enhance the turbulent reconnection efficiency to accelerate particles more efficiently, resulting in a hard spectral energy distribution. Our study provides a particular perspective on understanding turbulence properties and turbulent-reconnection-accelerated particles. [ABSTRACT FROM AUTHOR]

Synchrotron intensity and polarization gradients (SIG and SPG), proposed by Lazarian et al. and Lazarian & Yuen, present a new way to recover the mean magnetic field direction in the plane of the sky. To measure the magnetization level, Lazarian et al. suggested that the methods used in the context of the "Velocity Gradient Technique" could also be used on the SIG and SPG contexts. In this work we test the two proposed methods, named "top-base" and the circular standard deviation, "S," to obtain the level of magnetization from synchrotron emission. In order to test the methods, we generate synthetic observations from magnetohydrodynamic computer simulations, with Alfvénic Mach numbers, MA ∈ [0.2,1.7]. Using a Bayesian analysis we find that the circular standard deviations for the SIG and SPG methods are able to recover the magnetization for cases with signal-to-noise ratio ≳5. We found that for weak Faraday depolarization and different angles between the magnetic field direction and the line of sight the magnetization level can still be estimated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper studies how to employ synchrotron emission gradient techniques to reveal the properties of the magnetic field within the interstellar media. Based on data cubes of three-dimensional numerical simulations of magnetohydrodynamic turbulence, we explore spatial gradients of synchrotron emission diagnostics to trace the direction of the magnetic field. According to our simulations, multifarious diagnostics for synchrotron emission can effectively determine the potential direction of projected magnetic fields. Applying the synergies of synchrotron diagnostic gradients to the archive data from the Canadian Galactic Plane Survey, we find that multifarious diagnostic techniques make consistent predictions for the Galactic magnetic field directions. With the high-resolution data presently available from Low Frequency Array for radio astronomy and those in the future from the Square Kilometer Array, the synergies of synchrotron emission gradients are supposed to perform better in tracing the actual direction of interstellar magnetic fields, especially in the low-frequency Faraday rotation regime where the traditional synchrotron polarization measure fails. [ABSTRACT FROM AUTHOR]

In order to understand the main observational characteristics of the Galactic X-ray binary Cygnus X-3, we propose a radiation model in which high-energy electrons accelerate in the dissipation zone of a jet and produce nonthermal broadband emissions. Broadband spectral energy distributions are computed to compare the AGILE and Fermi LAT data with the multi-band data during soft X-ray spectral states. By fitting observations at different locations of the jet, we find that the emission region is rather compact and should be located at a distance of about one orbital radius. Our results can explain the current multi-frequency observations and also predict the TeV band emission. The model could be tested by a polarization measurement at IR band, and/or by a correlation study between the GeV and TeV bands once very-high-energy observations are available. [ABSTRACT FROM AUTHOR]