TY - THES

T1 - Effective mechanism and the source region of the stimulated ELF/VLF waves by high power HF radio waves

AU - Guo, Zhe

PY - 2021/12/31

Y1 - 2021/12/31

N2 - The ionosphere can be utilized as a natural plasma laboratory for the investigation of many nonlinear plasma processes by means of high-power, high-frequency radio waves, a process known as ionospheric heating.One of the most important effects of ionospheric heating by High Frequency (HF)waves, is the generation of ELF/VLF (extremely low frequency/very low frequency) waves by modulated heating. This area of research has been a focus of many investigations for almost fifty years since the most basic method of amplitude modulation was proposed.This dissertation introduces the main mechanisms of ionospheric heating as well as amplitude modulation and beat wave modulation in both D and F regions. Animportant limitation of amplitude modulation is its dependence on the ionospheric electrojet, which means in order to achieve better modulation effects, some strict spatio-temporal conditions must be met. In order to solve this problem, some possible methods have been proposed including beat wave modulation. However, due to the controversy of its mechanism and the source region of the stimulated ELF/VLF waves, it is not clear whether it is an electrojet-independent method or not, which has become one of the hot topics in recent years. This dissertation is focused on the identification of the mechanism and source region of beat wave modulation by means of constructing and simulation of physical models. The results are then compared to several observations reported in the literature in order to verify the validity of the proposed physical models.

AB - The ionosphere can be utilized as a natural plasma laboratory for the investigation of many nonlinear plasma processes by means of high-power, high-frequency radio waves, a process known as ionospheric heating.One of the most important effects of ionospheric heating by High Frequency (HF)waves, is the generation of ELF/VLF (extremely low frequency/very low frequency) waves by modulated heating. This area of research has been a focus of many investigations for almost fifty years since the most basic method of amplitude modulation was proposed.This dissertation introduces the main mechanisms of ionospheric heating as well as amplitude modulation and beat wave modulation in both D and F regions. Animportant limitation of amplitude modulation is its dependence on the ionospheric electrojet, which means in order to achieve better modulation effects, some strict spatio-temporal conditions must be met. In order to solve this problem, some possible methods have been proposed including beat wave modulation. However, due to the controversy of its mechanism and the source region of the stimulated ELF/VLF waves, it is not clear whether it is an electrojet-independent method or not, which has become one of the hot topics in recent years. This dissertation is focused on the identification of the mechanism and source region of beat wave modulation by means of constructing and simulation of physical models. The results are then compared to several observations reported in the literature in order to verify the validity of the proposed physical models.

U2 - 10.17635/lancaster/thesis/1160

DO - 10.17635/lancaster/thesis/1160

M3 - Master's Thesis

PB - Lancaster University

ER -