Experimental Study On Regulation Of Ionosphere-like Plasma Using Ring Electrode

The ionosphere,as an important region of the Earth’s upper atmosphere,has always been the focus of attention and research.The study of plasma instabilities in the ionospheric region is of both scientific and applied value.The ionosphere-like simulations performed in ground laboratories,in which the excitation and evolution of plasma instabilities are studied,not only have the advantages of being repeatable,adjustable,and having more high-precision diagnostic equipment available,but also are less expensive than starting a space observation mission,thus complementing the results of space observations and numerical simulations.The ionosphere at the equator and polar regions is a region of high incidence of plasma instability due to the influence of equatorial electrojet,polar electrojet,and polar region energetic particle precipitation,etc.In this region,the inhomogeneous distribution of plasma parameters such as fieldaligned currents,velocity shear,and density gradients is abundant,providing excellent conditions for the excitation of spatially distributed inhomogeneous instabilities.The height of the E layer,moreover,is characterized by its partial ionization,different magnetization of electrons and ions,which makes the instability processes in this height range unique.In order to reveal more detailed images of physical processes in the ionosphere and to investigate the contribution of non-uniform electric field and fieldaligned currents to the excitation and evolution of plasma instability in partially ionized plasma,we designed and developed two different configurations of ring electrodes for different experimental requirements.The modulation of the plasma density gradient,radial electric field,and field-aligned current were successfully realized by means of external regulation of bias conditions respectively.The successful realization of the inhomogeneous distribution of these plasma parameters excites the plasma waves at the same time.Spectrum analysis and wave propagation analysis were conducted.Finally,we drew a conclusion that the waves excited by the E × B shear flow come from the KH instability,and the waves excited by non-uniform field-aligned currents and density gradients are due to the CDEIC instability.The completion of this experiment lays the foundation for subsequent experiments on plasma instabilities and provides a reference for data on the use of ring electrodes to modulate plasma parameters.