月基观测地球等离子体层极紫外辐射特性

Moon-based imaging of earth plasmaspheric extreme ultraviolet radiation

研究了地球等离子体层的极紫外辐射特性,结果表明从月球上探测时地球等离子体层顶位于35 081.75 km以内,等离子体层结构的典型尺度量级为637.85 km,He＋30.4 nm辐射强度为0.02~11.4 Rayleigh。讨论了月球轨道运动特性和月球表面环境特性,结果显示在一个月球公转周期内,总观测时间约为12个地球日,极紫外观测仪器对地指向的纬度最大偏移约为7°,经度最大偏移约为6°。对月面的极紫外辐射分析表明,太阳峰年月面散射的极紫外辐射强度约为2.0 Rayleigh,与地球等离子体层辐射量级相当。根据SELENE数据,描述了极紫外观测仪器所在的5个拟着陆区的地貌特征,证明了月面散射的极紫外辐射不会进入观测仪器,其中虹湾区的地形最为理想。根据Apollo-12和Apollo-15太阳风数据分析了月面质子和电子通量,结果显示在太阳峰年,一年内两者的总流量均为约5×1015cm-2。根据Apollo-12局地观测,在一个月球周期内,月面温度变化为80~390 K。得到的结果为月基极紫外观测仪器设计提供了重要依据。

The extreme ultraviolet radiation properties of the earth plasmasphere was firstly studied,which shows that the plasmapause is mainly located near 35 081.75 km,the typical scale of the plasmasphere structures is 637.85 km,and the He＋ 30.4 nm emission intensity is between 0.02 and 11.4 Rayleigh when the plasmasphere is detected from the moon.Then,the orbital characteristics and surface environmental properties of the moon were described and it is pointed out that the total imaging period of an extreme ultraviolet imager is 12 d,in which the maximum latitudinal drift of the positioning of the camera is 7° while the maximum longitudinal drift is 6°.The extreme ultraviolet radiation of the lunar surface was analyzed,and results indicate that the extreme ultraviolet radiation reflected by lunar surface is 2.0 Rayleigh at solar maximum,which has the same order in the magnitude as compared with the plasmasphere emission.Based on the SELENE observation data,topographic properties in the five planned landing sites were explored,it proves that the extreme ultraviolet radiation reflected by lunar surface in these sites can not enter the field of view of the camera.For the five sites,Sinus Iridum is the most ideal site for moon-based extreme ultraviolet imaging.The proton and electron fluxes on the lunar surface were analyzed using Apollo-12 and Apollo-15 SWC experiment data,results show that the total fluences of protons and electrons are both approximately 5×1015 cm-2 in one-year period.During a lunation,the lunar surface temperature changes from 80 K at lunar night to 390 K at lunar noon according to Apollo-12 observation.Above results provide an important basis for the design of moon-based extreme ultraviolet imagers.