The study of wave-particle interactions in space plasmas is fundamental to understanding energy transport, particle acceleration, and plasma heating across the solar system. Despite decades of research, significant gaps remain in our knowledge of how plasma waves mediate cross-scale energy transfer, how wave-particle resonance mechanisms operate in realistic multi-component plasmas, and how to accurately diagnose plasma parameters in diverse space environments. This Research Topic aims to address these challenges by bringing together recent advances in three interconnected areas: (1) theoretical and observational studies of plasma wave modes and their interactions with charged particles in planetary magnetospheres, magnetosheaths, and the solar wind; (2) the development and application of quasi-thermal noise (QTN) spectroscopy as a precision diagnostic tool for space plasmas, including recent extensions to magnetized, weakly ionized, and collisional regimes; and (3) novel instrumentation and antenna design concepts for enhanced plasma wave measurements. By integrating perspectives from wave physics, plasma diagnostics, and instrumental development, this collection seeks to advance both fundamental understanding and practical capabilities in space plasma research.

Space plasmas throughout the solar system are inherently collisionless and multi-scale, where wave-particle interactions serve as the dominant mechanism for energy exchange between electromagnetic fields and charged particles. Recent multi-spacecraft missions including Cluster, MMS, and Parker Solar Probe have revealed a wealth of wave phenomena: from magnetosonic-whistler wave chains in the terrestrial foreshock to large-amplitude whistler waves in plasmaspheric plumes, and from magnetosheath jets observed across multiple planets to kinetic Alfvén waves driving particle precipitation. Concurrently, quasi-thermal noise spectroscopy has emerged as a powerful passive diagnostic technique that leverages thermal voltage fluctuations on electric field antennas to measure electron density and temperature with high accuracy. Recent theoretical advances have extended QTN analysis beyond the collisionless, unmagnetized regime to incorporate magnetization effects, collisional damping, and non-Maxwellian velocity distributions, significantly broadening its applicability to ionospheric and planetary plasma environments. These parallel developments create unprecedented opportunities for integrated studies that combine wave physics with advanced plasma diagnostics.

We welcome original research, review, and brief research report articles addressing, but not limited to, the following themes:

(1) Observational and theoretical studies of plasma waves including whistler-mode, kinetic Alfvén, magnetosonic, ion cyclotron, and electrostatic waves in planetary magnetospheres, magnetosheaths, and the solar wind.
(2) Wave-particle resonance mechanisms, cross-scale energy transfer chains, and particle acceleration processes;
(3) Magnetosheath dynamics, bow shock structures, and magnetospheric boundary layer physics.
(4) Quasi-thermal noise spectroscopy covering theoretical modeling, numerical simulations, and applications to magnetized, collisional, or multi-component plasmas.
(5) Antenna design and optimization for QTN and plasma wave measurements, including studies of dipole configurations and opening-angle effects on spectral response.
(6) Multi-spacecraft data analysis methods for identifying wave modes, boundary structures, and field geometries.

Interdisciplinary studies bridging observations, theory, simulations, and instrumentation are particularly encouraged. Manuscripts combining experimental data with theoretical analysis or numerical modeling are strongly preferred.

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Wave-Particle Interactions and Electrostatic Diagnostics in Space Plasmas