Electrostatic Thermal Noise in Magnetized Weakly Ionized Collisional Plasmas

Abstract Quasi‐thermal noise (QTN) spectroscopy is a plasma diagnostic technique that enables precise measurements of moments for the local electron velocity distribution function. Previous studies on the QTN technique applied to weakly ionized collisional plasma were limited by the assumptions of unmagnetized and Maxwellian distributions. In this paper, we extend prior research by considering collisional and a secondary hot Maxwellian distribution. Further analysis indicates that as the collision frequency increases, the peak power spectral density at the decreases. In addition, we find that the influence of collisions on low‐frequency cyclotron harmonic signals in a magnetized plasma is mainly related to the plasma‐to‐electron cyclotron frequency ratio , but also has non‐trivial dependencies on the plasma Debye Length . Finally, we observed that in eight representative cases, the plasma harmonic disappearance frequency ratio is generally ∼0.25. Our research provides valuable theoretical guidance for the future application of QTN techniques in detecting plasma parameters, especially for collision frequencies typical of Earth's ionosphere.