Quasithermal Noise in Magnetized Plasma: Theory and Simulations

Abstract Quasithermal noise (QTN) spectroscopy has been extensively used as an accurate tool to measure electron density and temperature in unmagnetized space plasmas. The observed spectrum depends on both antenna geometry and plasma kinetic properties. When considering the QTN signal of a magnetized plasma, the description becomes more complicated. We utilize particle-in-cell (PIC) simulations to study the QTN characteristics in magnetized plasmas based on Maxwellian and two-Maxwellian distributions. We compare these results with numerical computations, finding good agreement between the two. However, there are some minor differences. Specifically, when the angle between the wavevector ( k ) and the background magnetic field was 60°, clear harmonics appeared in the QTN signal from the numerical computations, whereas in the PIC simulations, these harmonics appeared at an angle of 80°. This discrepancy may be related to additional noise in the PIC simulation and our parameter limitations. In addition, Bernstein harmonics become more pronounced as the angle increases between <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>k</mml:mi> </mml:math> and the background magnetic field. These results demonstrate that PIC simulations can be used to more accurately characterize QTN signals in complex, magnetized systems.