RF wave injection experiments and plasma chamber experiments to investigate space plasma turbulence

Summary form only given. Laboratory experiments have been conducted with the Versatile Toroidal Facility (VTF) that is a large toroidal plasma device constructed for simulating the ionospheric plasmas. The VTF plasmas can be generated by the injected microwaves via the electron cyclotron resonance heating (ECRH) process, or by the injected electron beams, or by a Taylor discharge device. The VTF plasmas are mainly imposed by a toroidal magnetic field that can simulate the Earth´s magnetic flux. A small vertical field is also added to the toroidal field, forming a helical configuration of magnetic field. This helical field can guide electric current to flow from the bottomside to the topside of the plasma chamber, simulating the auroral ionospheric plasma environment. The electric current is produced by a hot cathode electron beam drive system. We will report our recent experiments on plasma turbulence that is believed to occur in the auroral ionosphere. Our RF wave injection experiments have been conducted at Arecibo, Puerto Rico, aimed at investigating the plasma modes that appear in the turbulent ionospheric plasmas, such as Langmuir waves, lower hybrid waves, ion acoustic waves, and purely growing modes. The RF wave-induced Langmuir waves were diagnosed by the 430 MHz radar. These Langmuir waves have both the frequency downshifted and the frequency upshifted spectra. Further, the Langmuir wave spectra recorded in the vertical wave injection experiments are quite different from those observed in oblique wave injection experiments.