| The radiation belt was discovered in 1958.Since then,the radiation belt has been explored and studied extensively.Because there are many high-energy electrons which will harm the orbiting space system seriously in the radiation belt,and these highenergy electrons have the possibility of sinking into the atmosphere,which will cause atmospheric chemistry problems and destroy the ozone layer.Therefore,in recent years,the researches on the radiation belt are very enthusiastic.Only by fully understanding the dynamic evolution of the entire radiation belt,can we predict space weather,thereby reducing or even avoiding losses caused by space disasters.In 1965,Benediktov et al.in the Soviet Union first observed the auroral kilometric radiation and reported it.Auroral kilometric radiation is abbreviated as AKR.Because its phase velocity is faster than the speed of light,and its source region is located in the high-latitude aurora region,and the wavelength is on the order of kilometers,it is also called superluminous auroral kilometric radiation.The auroral kilometric radiation is one of the strongest radio radiation,its frequency is 30-800kHz,and the power range of the aurora kilometric radiation is relatively high,about 107-109W.The explosion of the auroral kilometric radiation is generally accompanied by the injection of hot electrons and the occurrence of substorms.First,this paper analyzes four auroral kilometric radiation events which based on the data of the Arase satellite in the ERG project.Through the polarization observations of the Arase satellite,the specific mode of the auroral kilometric radiation of the four events were judged,and it was found that not only the right-handed extraordinary mode of auroral kilometric radiation,but also the left-handed ordinary mode of auroral kilometric radiation existed in the radiation belt.Gaussian fitting was performed on these four auroral kilometric radiation events,and the average diffusion coefficient of electron bounce was calculated.It was found that the area where cyclotron resonance occurred between the two modes of auroral kilometer radiation and electrons are concentrated in the small pitch angle region.The results also show that the two modes of auroral kilometric radiation mainly dominant the diffusion of electron momentum,which indicates that the two modes of auroral kilometric radiation may accelerate electrons effectively.Next,this paper parametrically studies the influence of the left-handed ordinary auroral kilometric radiation in the outer radiation belt with L=4.5 on the dynamic evolution process of high-energy electrons in the outer radiation belt.The study quantitatively calculated the pitch angle,momentum and cross pitch angle-momentum bounce-averaged diffusion coefficients of the left-handed ordinary auroral kilometric radiation at different peak frequencies,different normal angle distributions and different latitude distributions.The results show that the momentum diffusion coefficient is generally about 100 times larger than the pitch angle diffusion coefficient,which shows that momentum diffusion plays a dominant role in the interactions between the lefthanded ordinary wave and electrons.In addition,as the peak frequency of the lefthanded ordinary wave increases,the effective diffusion coefficient will gradually concentrate in the small pitch angle region,which may be due to the fact that the interaction between the left-handed ordinary wave and electrons is more concentrated in the low-frequency range.And the diffusion coefficient will change drastically due to the change of the latitude distribution of the left-handed ordinary wave.This result is consistent with the effects of latitude on the subluminal wave and the right-handed extraordinary auroral kilometric radiation from the previous study.Through parametric studies,it is found that the left-handed ordinary auroral kilometric radiation may significantly affect the dynamic evolution process of high-energy electrons in the outer radiation belt under appropriate conditions. |
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