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Plasma Sci. Technol. ›› 2019, Vol. 21 ›› Issue (7): 075301.doi: 10.1088/2058-6272/ab0bcd

• Astrophysics and Space Plasma • Previous Articles     Next Articles

Optimized analysis of ionospheric amplitude modulated heating parameters for excitation of very/extremely low frequency radiations

Jutao YANG (杨巨涛)1,2, Jianguo WANG (王建国)1,3, Qingliang LI (李清亮)2, Haiqin CHE (车海琴)2 and Shuji HAO (郝书吉)2   

  

  1. 1 School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China
    2 National Key Laboratory of Electromagnetic Environment, China Research Institute of Radiowave Propagation, Qingdao 266107, People’s Republic of China
    3 Northwest Institute of Nuclear Technology, Xi’an 710024, People’s Republic of China
  • Received:2018-09-18 Published:2019-03-01
  • Supported by:

    This work is supported by the Innovation Fund of China Electronics Technology Group Corporation (No. KJ1602004).

Abstract:

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 fHF may 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.

Key words: amplitude modulated heating, parameter optimization, duty cycle, heating frequency