A theoretical model which describes the small-scale irregularities excited by powerful high frequency （3–30 MHz） electromagnetic wave in ionosphere heating is investigated quantitatively in this paper. The model is...A theoretical model which describes the small-scale irregularities excited by powerful high frequency （3–30 MHz） electromagnetic wave in ionosphere heating is investigated quantitatively in this paper. The model is based on the transport equation in magnetic plasma and mode conversion from electromagnetic wave to electrostatic wave in ionospheric modification.Threshold electric field for exciting small-scale （meter scale） irregularities and spatial spectra of irregularities are analytically calculated by this model. The results indicate that background electron density and geomagnetic field play an important role for the threshold electric field and the spatial scale of the electron density irregularities. The results demonstrate that the electric field threshold increases with the decrease of the spatial scale of the irregularities. For exciting meter scale irregularities, the threshold electric field is about tens of mV m^（-1）. The theoretical results are consistent with those of the experiments.展开更多
Nonlinear instability in electrically charged jets is studied using the governing electro-hydrodynamic equations describing stretching and thinning of a liquid jet. A jet flow system subject to both space and time evo...Nonlinear instability in electrically charged jets is studied using the governing electro-hydrodynamic equations describing stretching and thinning of a liquid jet. A jet flow system subject to both space and time evolving disturbances is considered. At the linear stage, the Rayleigh and conducting jet flow instability modes are uncovered.Nonlinear instability in the flow is explored via triad resonant waves which uncover favorable operating modes not previously detected in the linear study of the problem. In particular, the jet radius is significantly reduced, and the electric field of the jet is properly oriented under the nonlinear study. It is found that taking into account the resonance triad modes provides a better mathematical description of a jet that stretches and thins due to tangential electric field effects. Both linear and nonlinear instability results in the jet flow system are presented and discussed.展开更多
In the frame of weak nonlinear theory,a set of equations depicting the nonlinear interactions of barotropic Rossby waves are derived,the topography and Ekman fric-tion are involved in the equations.Starting from the e...In the frame of weak nonlinear theory,a set of equations depicting the nonlinear interactions of barotropic Rossby waves are derived,the topography and Ekman fric-tion are involved in the equations.Starting from the equations,we investigate the in -teraction of three Rossby wave packets with narrow-spread in wave vectors.When an intense primary pump Rossby wave with amplitude larger than a threshold propagates through the atmosphere ,the amplitude of one Rossby wave packet with scale greaterthan the primary one and one Rossby wave packet with scale smaller than the primaryone grow exponentially through three wave interactions,the intrinsic frequencies of the secondary waves can be varied,The threshold and the variation of the intrinsic frequ-encies of the secondary waves are related to the Ekman friction frequency dismatchtopography and spatial evolution of the secondary Rossby wave packets.展开更多
基金supported by National Natural Science Foundation of China(NSFC grants 41204111,4157414641774162 and 41704155)China Postdoctoral Science Foundation(2017M622504)
文摘A theoretical model which describes the small-scale irregularities excited by powerful high frequency （3–30 MHz） electromagnetic wave in ionosphere heating is investigated quantitatively in this paper. The model is based on the transport equation in magnetic plasma and mode conversion from electromagnetic wave to electrostatic wave in ionospheric modification.Threshold electric field for exciting small-scale （meter scale） irregularities and spatial spectra of irregularities are analytically calculated by this model. The results indicate that background electron density and geomagnetic field play an important role for the threshold electric field and the spatial scale of the electron density irregularities. The results demonstrate that the electric field threshold increases with the decrease of the spatial scale of the irregularities. For exciting meter scale irregularities, the threshold electric field is about tens of mV m^（-1）. The theoretical results are consistent with those of the experiments.
基金Project supported by the National Science Foundation of U.S.A.(No.DMS-0946431)
文摘Nonlinear instability in electrically charged jets is studied using the governing electro-hydrodynamic equations describing stretching and thinning of a liquid jet. A jet flow system subject to both space and time evolving disturbances is considered. At the linear stage, the Rayleigh and conducting jet flow instability modes are uncovered.Nonlinear instability in the flow is explored via triad resonant waves which uncover favorable operating modes not previously detected in the linear study of the problem. In particular, the jet radius is significantly reduced, and the electric field of the jet is properly oriented under the nonlinear study. It is found that taking into account the resonance triad modes provides a better mathematical description of a jet that stretches and thins due to tangential electric field effects. Both linear and nonlinear instability results in the jet flow system are presented and discussed.
文摘In the frame of weak nonlinear theory,a set of equations depicting the nonlinear interactions of barotropic Rossby waves are derived,the topography and Ekman fric-tion are involved in the equations.Starting from the equations,we investigate the in -teraction of three Rossby wave packets with narrow-spread in wave vectors.When an intense primary pump Rossby wave with amplitude larger than a threshold propagates through the atmosphere ,the amplitude of one Rossby wave packet with scale greaterthan the primary one and one Rossby wave packet with scale smaller than the primaryone grow exponentially through three wave interactions,the intrinsic frequencies of the secondary waves can be varied,The threshold and the variation of the intrinsic frequ-encies of the secondary waves are related to the Ekman friction frequency dismatchtopography and spatial evolution of the secondary Rossby wave packets.
