The energy transformation from electromagnetic wave to plasmas polaritons in overdense plasma is investigated by using the theory of hydrodynamics in the thin cylinder limit and surface wave resonator. The grating experiment certifies the excitation of the surface wave. Through studying the role of the magnetic field in excitation of the surface wave and analyzing the frequency domain spectrum of the reflected wave, the time series of reflection, transmission and plasma density are diagnosed when the electromagnetic wave transforms into the surface wave. The experimental scheme of Bliokh [Phys. Rev. Lett. 95, 165003 (2005)] is improved. A steady overdense plasma in a cylindrical cavity is obtained by dc high voltage discharging and measurement is taken in series. The diffraction grating is fixed in optimum position after the distance from it to the chamber is adjusted. The reflection ratios of plasma and a piece of tinfoil are compared to avoid the effect of the standing wave. The effect of incident polarization is discussed and a measurement result is obtained with a 70Gauss magnetic field. Further research on scanning measurement reveals that the collision rate is the only determinant element of the half absorption width. Numerical simulation is given, based on the theory of surface plasmons (SPs). The experimental data agree with the numerical simulation well near the resonance frequency f=5GHz, while on the trailing edge, the curve is obviously expanded. The mechanism of these phenomena is very complex and other conceivable factors must exist during the excitation of SPs, which should be studied in the further research.

Transversely accelerated ions and the associated heating of the high‐latitude ionosphere have been attributed to broadband extremely low frequency (BBELF) turbulence. Controlled laboratory tests of the hypotheses on the formation mechanism of BBELF waves have involved only a few examples, e.g., current‐driven and shear‐driven instabilities. In this work, electrostatic fluctuations in the ion cyclotron frequency range have been excited by inhomogeneous energy‐density‐driven instability (IEDDI). This was achieved using the interpenetrating plasma method with a much larger electric field scale size LE comparable to the ion gyroradius ρi, which was challenging earlier because of plasma conditions. The peak frequency of the IEDDI spectrum falls as low as ω≈0.3ωci, where ωci is ion cyclotron frequency. This is an interesting result because the previous attempts could not produce such low‐frequency IEDDI, although it was known theoretically to be possible. The observations made by FAST, Freja, and Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites might be explainable in terms of the reported experimental results.

In this letter, we experimentally investigated the transmission of microwaves through a single subwavelength slit surrounded by periodic grooves in metallic aluminum plates. Significant transmission enhancement (16.2-fold) and angular confinement (±18°) were observed at X-band microwave frequencies (8–12GHz). We demonstrated that the coupled surface plasmons were involved in the interesting transmission process. The little angular divergence was attributed to the periodic structures of the exit surface. The experimental results show good agreement with theory and are of relevance not only for further understanding the underlying science but also for enlarging applications based on this phenomenon.

Laboratory observations of spontaneous emission of Alfvénic branch oscillations generated by a strong inhomogeneous plasma flow are reported in this work. Electrostatic KH instabilities in the subcyclotron frequency range were excited using the interpenetrating plasma method. Experiments indicate that spontanegeous Alfvénic branch oscillations occur when the plasma inhomogeneity increases above a threshold. The electromagnetic wave amplitude spreads out radially over a much larger extent than the electrostatic mode. Theoretical calculations using the MHD method also support the experimental observation. The result has important application in understanding the cross‐scale transport of particles and energies in astrophysical, space, and laboratory plasmas.

In this work, the design and construction of the Keda Space Plasma EXperiment (KSPEX), which aims to study the boundary layer processes of ionospheric depletions, are described in detail. The device is composed of three stainless-steel sections: two source chambers at both ends and an experimental chamber in the center. KSPEX is a steady state experimental device, in which hot filament arrays are used to produce plasmas in the two sources. A Macor-mesh design is adopted to adjust the plasma density and potential difference between the two plasmas, which creates a boundary layer with a controllable electron density gradient and inhomogeneous radial electric field. In addition, attachment chemicals can be released into the plasmas through a tailor-made needle valve which leads to the generation of negative ions plasmas. Ionospheric depletions can be modeled and simulated using KSPEX, and many micro-physical processes of the formation and evolution of an ionospheric depletion can be experimentally studied.