Effects of wave trapping and ducting inside plasma density depletions are studied in a laboratory magnetoplasma

Research on upper hybrid trapping and ducting by striations is crucial to understand the process of electromagnetic energy transfer, plasma heating dynamics and plasma transport processes in the ionosphere. Because of the scale and height of the Earth’s ionosphere, in situ study of the striations and trapped quasi-electrostatic waves in the ionosphere are nearly impossible.

Upper hybrid wave trapping and ducting plays a significant role in magnetized plasmas, such as in tokamaks, the outer ionosphere and in the solar corona. Starodubtsev et al. studied the effects of wave trapping and ducting using laboratory model experiments. They discovered the effects of upper hybrid wave ducting by small-scale plasma depletions can determine the plasma heating dynamics, as well as electromagnetic energy balance and transport processes during ionospheric experiments.

The authors conducted their experiments in a laboratory plasma chamber, where an axially magnetized and uniform plasma column was produced in repetitive pulses for careful study. From analysis of the dispersion of waves in the magnetoplasma, the mechanism of upper hybrid wave ducting in a density depletion became clear.

“Our results for laboratory plasma have confirmed and shown a necessity of taking oblique propagation of the upper hybrid waves in ionospheric experiments,” Mikhail Starodubtsev said.

Spacecraft and rocket experimental research conducted in the ionosphere takes into account the combination of ionospheric heating experiments and upper hybrid wave trapping and ducting laboratory research.

The authors intend on expanding the ambient plasma parameters to structure them more similarly to the ones in the ionospheric active experiments, with multiple electron gyroresonances as their focus.

Source: “Ducting of upper-hybrid waves by density depletions in a magnetoplasma with weak spatial dispersion,” by Mikhail Starodubtsev, Sergey Korobkov, Mikhail Gushchin, Savely Grach, and Vladimir Nazarov, Physics of Plasmas (2019). The article can be accessed at https://doi.org/10.1063/1.5099338 .