会議発表論文 Lunar Surface Charging and Electrostatic Lofting of Lunar Dust Particles under Different Solar Wind Conditions and Solar Ultraviolet Radiation

Orger, Necmi Cihan  ,  Cordova-Alarcon, J. Rodrigo  ,  Toyoda, Kazuhiro  ,  Cho, Mengu  ,  Orger, Necmi Cihan  ,  Cordova-Alarcon, J. Rodrigo  ,  豊田, 和弘  ,  趙, 孟佑

内容記述
Lunar surface is electrically charged by continuous flux of ambient plasma as well as exposure to solar radiation. As the Moon orbits the Earth, its plasma environment varies according to its location with respect to the Earth and the Sun. Lunar surface charging is dependent on the electric current sources such as photoemission of electrons by solar irradiation, the collection of electrons and ions from ambient plasma and the secondary emission of electrons from the surface. These current sources can be used to determine the surface potential and electric field, and these values can be highly variable as the current sources alter with time. It has been suggested that lunar horizon glow is produced by forward scattering of the sunlight by electrically charged dust grains that are lofted above the lunar terminator; however, there are significant uncertainties about its physical mechanism. Even though previous laboratory experiments have suggested that intermediate size particles are easier to be lofted from surface by electrostatic forces, the observations of Apollo and Surveyor missions pointed out that smaller size particles in micron to submicron range were responsible for this phenomenon. In our work, various conditions are investigated to find out how surface potential, electric field and Debye length are altered with different parameters. First, it has been seen that subsolar point surface potential is significantly depending on photoemission electrons and solar wind electron current. Second, terminator region surface potential is highly depending on solar wind electron current and, in some cases, ion current. Third, a solar flare event produces strong electric field on subsolar point since most of the photoelectrons are trapped above the positively charged surface. In addition, these results showed that zero potential occurs between subsolar point and terminator region as it is expected, and its location is determined by the photoelectron emission and ambient electron current to the surface dominantly. For these reasons, fast and slow solar wind conditions as well as CME passage on 1-3 May 1998 have been investigated in order to understand nominal and extreme conditions. According to these results, laboratory experiments will be performed in order to understand the electrostatic forces on dust particles and the conditions to launch these particles from the surface. Relative to this work, a CubeSat mission is currently being developed in Kyushu Institute of Technology to observe lunar horizon glow.
Meeting Information: The 13th Spacecraft Environment Symposium (November 1-2, 2016. National Institute of Information and Communications Technology), Koganei, Tokyo, Japan
Physical characteristics: Original contains color illustrations
会議情報: 第13回宇宙環境シンポジウム (2016年11月1日-2日. 情報通信研究機構 本部 国際会議室), 小金井市, 東京
形態: カラー図版あり
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https://repository.exst.jaxa.jp/dspace/bitstream/a-is/599464/1/AA1630038015.pdf

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