It is now well known that amplitude modulated(AM) high frequency(HF) radio wave transmissions into the ionosphere can be used to generate very/extremely low frequency(VLF/ELF) radio waves using the so-called ‘electro...It is now well known that amplitude modulated(AM) high frequency(HF) radio wave transmissions into the ionosphere can be used to generate very/extremely low frequency(VLF/ELF) radio waves using the so-called ‘electrojet antenna’. Duty cycle and heating frequency are analyzed and discussed with the lower-ionosphere modulated heating model, so as to improve the radiation efficiency of VLF/ELF waves in AM ionospheric heating experiments. Based on numerical simulation, the ranges of parametric selectivity in optimal duty cycle and heating frequency( fHF) are derived. The International Reference Ionosphere 2015(IRI-2015) model and two-parameter model are used to predict background electron density profiles, and optimized ranges of duty cycle for different density profiles are analyzed and compared. The influences of wave polarizations on optimal duty cycle are also discussed. It is shown that intensity of the VLF/ELF equivalent radiation source(M) firstly rises and then falls with the increase of duty cycle. When using the IRI model, M peaks at a duty cycle of 50%, optimally ranging from 40%-70%. For the two-parameter model case, an optimal duty cycle is 40% and the optimized ranges vary from 30%-60%. Heating with an X-mode polarization is more efficient than with the O-mode case in VLF/ELF wave generation. Nevertheless, an optimal duty cycle is almost independent of HF wave polarizations. To obtain better VLF/ELF generation, optional fHFmay be 0.8-0.9 times of foE for the O-mode heating and 0.75-0.85 times for the X-mode polarization case. Finally, the variations of these two parameters in different latitudes are discussed.展开更多
A self-consistent fluid model is developed to investigate the radial distributions of dusty plasma parameters in a DC glow discharge,in which the extended fluid approach of plasma particles and the transport equations...A self-consistent fluid model is developed to investigate the radial distributions of dusty plasma parameters in a DC glow discharge,in which the extended fluid approach of plasma particles and the transport equations of dust particles are coupled.The electrical interaction between charged dust particles is considered in the model.The time evolution of radial distributions of dust density,plasma density,the radial component of electric field and the forces acting on dust particles when dust density tends to be stable,are obtained and analyzed under different discharge currents and dust particle radii.It is shown that the dust density structure is determined mainly by the radial electrostatic force,thermophoretic force and ion drag force in the discharge tube,and both discharge current and dust particle radius have an obvious effect on the transport processes of dust particles.The dust particles gather in the central region of the discharge tube for low discharge current and small dust radius,then dust voids are formed and become wider when the discharge current and dust radius increase.The plasma parameters in the dust gathering region are obviously affected by the dust particles due to the charging processes of electrons and ions to the dust surface.展开更多
During the course of ionospheric heating experiments, researchers at the European Incoherent Scatter Scientific Association (EISCAT) observed an apparent electron density enhancement. The enhancement extended over a w...During the course of ionospheric heating experiments, researchers at the European Incoherent Scatter Scientific Association (EISCAT) observed an apparent electron density enhancement. The enhancement extended over a wide range of altitudes, above the reflection altitude of the high-frequency pump wave. However, whether this enhancement actually corresponds to a true enhancement in electron density remains an open question. When the dispersion relation of ion acoustic waves is followed, the frequency ratio of the enhanced ion line to the background ion line suggests that the profile of the effective ion mass may have remained unchanged. Furthermore, the solar radio flux and ion drift velocity indicate no significant changes in the ion species and their densities. In conclusion, the electron density enhancement observed at EISCAT should not, in fact, be considered a true enhancement.展开更多
基金supported by the Innovation Fund of China Electronics Technology Group Corporation (No. KJ1602004)
文摘It is now well known that amplitude modulated(AM) high frequency(HF) radio wave transmissions into the ionosphere can be used to generate very/extremely low frequency(VLF/ELF) radio waves using the so-called ‘electrojet antenna’. Duty cycle and heating frequency are analyzed and discussed with the lower-ionosphere modulated heating model, so as to improve the radiation efficiency of VLF/ELF waves in AM ionospheric heating experiments. Based on numerical simulation, the ranges of parametric selectivity in optimal duty cycle and heating frequency( fHF) are derived. The International Reference Ionosphere 2015(IRI-2015) model and two-parameter model are used to predict background electron density profiles, and optimized ranges of duty cycle for different density profiles are analyzed and compared. The influences of wave polarizations on optimal duty cycle are also discussed. It is shown that intensity of the VLF/ELF equivalent radiation source(M) firstly rises and then falls with the increase of duty cycle. When using the IRI model, M peaks at a duty cycle of 50%, optimally ranging from 40%-70%. For the two-parameter model case, an optimal duty cycle is 40% and the optimized ranges vary from 30%-60%. Heating with an X-mode polarization is more efficient than with the O-mode case in VLF/ELF wave generation. Nevertheless, an optimal duty cycle is almost independent of HF wave polarizations. To obtain better VLF/ELF generation, optional fHFmay be 0.8-0.9 times of foE for the O-mode heating and 0.75-0.85 times for the X-mode polarization case. Finally, the variations of these two parameters in different latitudes are discussed.
基金supported by the Stable-Support Scientific Project of China Research Institute of Radiowave Propagation(No.132101W07)National Natural Science Foundation of China(No.12105251)National Key Laboratory Foundation Electromagnetic Environment(Nos.A382101001,A382101002 and A152101731-C02).
文摘A self-consistent fluid model is developed to investigate the radial distributions of dusty plasma parameters in a DC glow discharge,in which the extended fluid approach of plasma particles and the transport equations of dust particles are coupled.The electrical interaction between charged dust particles is considered in the model.The time evolution of radial distributions of dust density,plasma density,the radial component of electric field and the forces acting on dust particles when dust density tends to be stable,are obtained and analyzed under different discharge currents and dust particle radii.It is shown that the dust density structure is determined mainly by the radial electrostatic force,thermophoretic force and ion drag force in the discharge tube,and both discharge current and dust particle radius have an obvious effect on the transport processes of dust particles.The dust particles gather in the central region of the discharge tube for low discharge current and small dust radius,then dust voids are formed and become wider when the discharge current and dust radius increase.The plasma parameters in the dust gathering region are obviously affected by the dust particles due to the charging processes of electrons and ions to the dust surface.
基金supported by research organizations in China (CRIRP), Finland (SA), Japan (NIPR and STEL), Norway (NFR), Sweden (VR), and the United Kingdom (NERC)supported by the Taishan Scholars Project of Shandong Province (Grant No. ts20190968)supported by the foundation of National Key Laboratory of Electromagnetic Environment (Grant No. 6142403230303)
文摘During the course of ionospheric heating experiments, researchers at the European Incoherent Scatter Scientific Association (EISCAT) observed an apparent electron density enhancement. The enhancement extended over a wide range of altitudes, above the reflection altitude of the high-frequency pump wave. However, whether this enhancement actually corresponds to a true enhancement in electron density remains an open question. When the dispersion relation of ion acoustic waves is followed, the frequency ratio of the enhanced ion line to the background ion line suggests that the profile of the effective ion mass may have remained unchanged. Furthermore, the solar radio flux and ion drift velocity indicate no significant changes in the ion species and their densities. In conclusion, the electron density enhancement observed at EISCAT should not, in fact, be considered a true enhancement.
