Review of ionospheric irregularities and ionospheric electrodynamic coupling in the middle latitude region

作     者：Yi Liu Chen Zhou Tong Xu Qiong Tang ZhongXin Deng GuanYi Chen ZhuangKai Wang Yi Liu;Chen Zhou;Tong Xu;Qiong Tang;ZhongXin Deng;GuanYi Chen;ZhuangKai Wang

作者机构：Department of Space PhysicsSchool of Electronic InformationWuhan UniversityWuhan 430072China National Key Laboratory of Electromagnetic EnvironmentChina Research Institute of Radiowave PropagationQingdao 266107China 

出 版 物：《Earth and Planetary Physics》 (地球与行星物理（英文版）)

年 卷 期：2021年第5卷第5期

页      面：462-482页

核心收录：

学科分类：070802[理学-空间物理学] 07[理学] 0708[理学-地球物理学] 

基　　金：supported by the National Natural Science Foundation of China (No. 41574146, 41774162, 42074187) the National Key R&D Program of China (No. 2018YFC1503506) the Excellent Youth Foundation of Hubei Provincial Natural Science Foundation (No. 2019CFA054) the Foundation of the National Key Laboratory of Electromagnetic Environment (No. 20200101) 

主　　题：ionospheric irregularity plasma instability neutral wind polarized electric field ionospheric electrodynamic coupling 

摘      要：This paper briefly reviews ionospheric irregularities that occur in the E and F regions at mid-latitudes. Sporadic E(ES) is a common ionospheric irregularity phenomenon that is first noticed in the E layer. ES mainly appears during daytime in summer hemispheres, and is formed primarily from neutral wind shear in the mesosphere and lower thermosphere(MLT) region. Field-aligned irregularity(FAI) in the E region is also observed by Very High Frequency(VHF) radar in mid-latitude regions. FAI frequently occurs after sunset in summer hemispheres, and spectrum features of E region FAI echoes suggest that type-2 irregularity is dominant in the nighttime ionosphere. A close relationship between ES and E region FAI implies that ES may be a possible source of E region FAI in the nighttime ionosphere. Strong neutral wind shear, steep ES plasma density gradient, and a polarized electric field are the significant factors affecting the formation of E region FAI. At mid-latitudes, joint observational experiments including ionosonde, VHF radar, Global Positioning System(GPS) stations, and all-sky optical images have revealed strong connections across different scales of ionospheric irregularities in the nighttime F region, such as spread F(SF), medium-scale traveling ionospheric disturbances(MSTID), and F region *** suggest that different scales of ionospheric irregularities are generally attributed to the Perkins instability and subsequently excited gradient drift instability. Nighttime MSTID can further evolve into small-scale structures through a nonlinear cascade process when a steep plasma density gradient exists at the bottom of the F region. In addition, the effect of ionospheric electrodynamic coupling processes, including ionospheric E-F coupling and inter-hemispheric coupling on the generation of ionospheric irregularities, becomes more prominent due to the significant dip angle and equipotentiality of magnetic field lines in the mid-latitude ionosphere. Polar