Laboratory Evidence of a Pre‐Existing Instability That Can Enhance the Ionospheric Heating Efficiency

• Published in: Geophysical research letters Vol. 48; no. 9
• Main Authors: Ling, Yiming, Liu, Yu, Lei, Jiuhou, Li, Minchi, Liu, Xiangqun
• Format: Journal Article
• Language: English
• Published: 16.05.2021
• Subjects: Ionosphere; ionospheric heating; laboratory plasma
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL092560

Ionospheric heating by high‐power electromagnetic waves is a powerful and efficient tool to study plasma physics as the ionosphere is used as a nature plasma laboratory. An important and long‐standing issue is how to improve the heating efficiency. It is difficult to uncover all the underlying physical processes that influence the heating efficiency in actual ionospheric experiments. Therefore, controlled experiments have been designed and conducted in a laboratory plasma facility to study the high‐frequency heating processes in an ionospheric‐like collisional plasma. The energy of the injected wave was transferred into the plasma through nonlinear interactions, such as the parametric decay instability (PDI). Our results suggest that the existing background wave mode could significantly decrease the excitation threshold of the parametric instability, indicating that the PDI can be much easily excited. Plain Language Summary The ionosphere, the ionized part of Earth's upper atmosphere from about 60 to 1,000 km, has a significant impact on daily activities of humankind. Since the 1970s, ionospheric heating by high‐power high‐frequency (HF) waves has been widely recognized as a powerful tool to artificially modify the ionosphere. Many important physical processes are also studied as the ionosphere is used as a plasma laboratory. On the other hand, such control of ionospheric conditions may have practical applications in radio communication. These ground‐based heating facilities are equipped with high‐power HF transmitters and a variety of diagnostic instruments for monitoring the response of the ionosphere and upper atmosphere. Laboratory modeling of the particular phenomenon in space environment began to develop, and could be applied to understand the physical mechanism of the observations. This work provides an experimental evidence that the existing background wave mode could significantly decrease the excitation threshold of the parametric instability. Therefore, it can be potentially useful to improve efficiency in the active heating experiments. Key Points Controlled experiments have been performed to study high‐frequency heating processes in an ionospheric‐like collisional plasma Parametric decay instability generated by the electromagnetic wave injection was observed in the laboratory A background instability can obviously decrease the excitation threshold of the parametric decay instability