H. Fu

Irregularities Associated With Creation of Dusty Plasmas in the Near-Earth Space Environment

Plasma irregularities associated with the creation of an artificial dust layer in the Earths ionosphere are investigated with a 2-D plasma simulation model. The scenario considered in this investigation is the production of electron irregularities due to growth of a plasma instability driven by inhomogeneities in the boundary between the background plasma and the expanding charged dust layer. The mechanism is shown to effectively generate irregularities for early times after a localized release of dust for the parameter regimes of upcoming space experiments.

Nonlinear Evolution of the Dust Acoustic Instability in Artificially Created Dusty Space Plasmas

A 2-D hybrid electrostatic model is used to investigate the dust acoustic instability driven by an ion beam. To understand the generation and the nonlinear electrostatic waves, we investigate possible parameter regimes for the dust acoustic instability. The principal application involves the Charged Aerosol Release Experiment in the ionosphere, but also potential applications are for the planetary ring system of Saturn. The plasma background ions and charged dust are treated as discrete particles, whereas electrons are dealt with as a Boltzmann fluid. A Monte Carlo collision model is adopted to deal with the ion-neutral collisions. The kinetic dispersion relation is numerically solved to investigate effects of the ion drift velocity and the dust charge and density on the wave growth rate and the wave propagation direction. The simulation results agree with linear analysis of the instability, which also shows that the most unstable dust acoustic wave may obliquely propagate to the streaming direction. This may be important for radar diagnostics. The wave saturates by trapping dust. The waves damp out as the ion-neutral collision frequency increases comparable with the wave growth rate, and more importantly, such collision may lead to unstable waves propagating even further off the streaming direction.

Model for charged dust expansion across a magnetic field

Plasma fluctuations arise in the boundary region between charged dust clouds and background plasmas. A self-consistent computational model is developed to study expansion of a charged dust cloud across a magnetic field, creation of the inhomogeneous boundary layer and associated processes. The charging of the dust particulates produces a boundary layer and associated ambipolar electric field. This ambipolar field provides a source for low frequency dust acoustic waves in unmagnetized plasmas. A background magnetic field if sufficiently strong, may impact the dust acoustic wave evolution and dust density structures due to E×B and diamagnetic current generation. The dust acoustic density fluctuation generation across a strong magnetic field (ωpe/Ωce≪1) may be suppressed as compared to an unmagnetized dusty plasma, which will be discussed. Fluctuations generated at longer timescales propagating along the dust boundary layer will also be investigated in the lower hybrid and dust lower hybrid frequency range. ...

Nonlinear evolution of the ion acoustic instability in artificially created dusty space plasmas

A 2-D hybrid electrostatic model is used to investigate the dust acoustic instability driven by an ion beam. To understand the generation and the nonlinear electrostatic waves, we investigate possible parameter regimes for the dust acoustic instability. The principal application involves the Charged Aerosol Release Experiment in the ionosphere, but also potential applications are for the planetary ring system of Saturn. The plasma background ions and charged dust are treated as discrete particles, whereas electrons are dealt with as a Boltzmann fluid. A Monte Carlo collision model is adopted to deal with the ion-neutral collisions. The kinetic dispersion relation is numerically solved to investigate effects of the ion drift velocity and the dust charge and density on the wave growth rate and the wave propagation direction. The simulation results agree with linear analysis of the instability, which also shows that the most unstable dust acoustic wave may obliquely propagate to the streaming direction. This may be important for radar diagnostics. The wave saturates by trapping dust. The waves damp out as the ion-neutral collision frequency increases comparable with the wave growth rate, and more importantly, such collision may lead to unstable waves propagating even further off the streaming direction.

New stimulated electromagnetic emission experiment at EISCAT

Observations of secondary radiation, Stimulated Electromagnetic Emission (SEE), produced during ionospheric modification experiments using ground-based high-power high frequency HF radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating Magnetized Stimulated Brillouin scatter MSBS and Stimulated Ion Bernstein scatter SIBS in the SEE spectrum. Narrowband SEE features have not been observed at EISCAT before. Narrowband MSBS spectrums are compared to such behavior previously observed at HAARP. Preliminary analyses of SEE data show observation of ion acoustic emission lines due to stimulated Brillouin scatter during the 2012 July EISCAT campaign. For varying heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics whereas electron temperature enhancement weakens measured by EISCAT/UHF radar.

Stimulated Brillouin scattering in magnetized ionospheric plasmas

We compare observations of Stimulated Brillouin scattering produced during ionospheric modification experiments using ground-based high-power high frequency HF radio waves at both the High Frequency Active Auroral Research Program (HAARP) and the European Incoherent scatter (EISCAT).

Investigation of magnetized dusty plasmas in the laboratory and near-earth space environment

The field of dusty plasmas has become a vigorous and established area of research for a number of decades now. In this work, two computational models are mainly developed to study possible plasma turbulence during the charged aerosol release experiments in space plasmas. Meanwhile, its applications for magnetized dusty plasmas for complex plasma research with upcoming experiment facilities at Auburn University is considered. Two new hybrid and full fluid two-dimensional computational models have been developed to investigate instabilities in nonuniform magnetized dusty plasmas. The magnetic fields have been applied to study the effect on plasma wave excitation.

Investigation of Stimulated Electromagnetic Emission SEE during second electron gyro-harmonic heating

Features in the Stimulated Electromagnetic Emission (SEE) spectrum during heating near the second electron gyro-harmonic frequency have recently attracted significant attention due to their possible connection to artificial airglow and artificially generated ionization layers. Experimentally, three new phenomenologically related spectral features within 1 kHz of the heater frequency have been recently discovered: (1) discrete narrowband spectral structures ordered by ion gyro-frequency, (2) broadband features with power spectral density maximum near 500 Hz and (3) the broadband features with embedded ion gyro-harmonic structures.