Aliaksandr Melnichenka

arXiv2026

Recovering 3D Magnetic Turbulence from Single-Frequency Faraday Screens

Statistics of polarized synchrotron radiation carry information about the properties of the underlying turbulence. Different statistical measures constructed from observables probe turbulence properties in different ways. We consider a setup in which synchrotron radiation is emitted in a distant volume and then passes through a turbulent screen that induces Faraday rotation. Using both MHD simulations and synthetic turbulence spectra, we explore the spectrum of observed polarization directions measured at a single frequency as a diagnostic for recovering the statistics of turbulence in both the emitting region and the Faraday-rotation screen. We compare these results with our analytical expectations. We also compare the spectrum of polarization direction (SPD) with the wavelength-derivative diagnostic introduced and analytically explored by Lazarian \& Pogosyan. We demonstrate that the SPD exhibits greater sensitivity to turbulence in the Faraday screen. We provide an observer-friendly criterion to determine whether the SPD samples turbulence in the synchrotron-emitting region or in the Faraday screen. These results open a practical pathway for extracting turbulence statistics from existing and forthcoming single-band radio polarimetry.

astro-ph.GA↗

arXiv2025

Spontaneous Running Waves and Self-Oscillatory Transport in Dirac Fluids

We predict hydrodynamic Turing instability of current-carrying Dirac electron fluids that drives spontaneous self-oscillatory transport. The instability arises near charge neutrality, where carrier kinetics make current dissipation strongly density dependent. Above a critical drift velocity, a uniform electronic flow becomes unstable and undergoes a dynamical transition to a state with coupled spatial modulation and temporal oscillations--an electronic analogue of Kapitsa roll waves in viscous films. The transition exhibits two clear signatures: a nonanalytic, second-order-like onset in the time-averaged current and narrow-band electromagnetic emission at a tunable washboard frequency $f=u/λ$. Although reminiscent of sliding charge-density waves, the mechanism is intrinsic and disorder independent. Owing to the small effective mass of Dirac carriers, hydrodynamic time scales translate into emission frequencies in the tens to hundreds of gigahertz range, establishing Dirac materials as a platform for high-frequency self-oscillatory electron hydrodynamics.

cond-mat.mes-hall↗