Improving Radio Transmission Through a Dense Plasma via Electron-Neutral Collisions

Abstract

Radio transmission through ionized media is a common requirement in several applications, including high-speed vehicles traveling in Earth's atmosphere and ionosphere. The plasma surrounding a vehicle prevents efficient radiation at typical radio frequencies. Investigating potential methods to improve transmission efficiency is thus an active area of research. Here, the role of electron-neutral collisions is investigated. It is first shown that for a simplified model of a homogeneous plasma slab, electron-neutral collisions can considerably improve radio transmission below the plasma frequency. Improved transmission at low frequencies due to collisions is confirmed in a realistic inhomogeneous case using an finite difference time domain simulation, thus demonstrating a potential strategy for circumventing shielding from plasma. Although electron-neutral collisions are typically associated with elevated radio wave absorption in plasmas, for frequencies below the plasma frequency, collisions enhance transmission through ionized media, yielding a ''collision frequency window.''