Lunar surface potential and electric field
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摘要
The Moon has no significant atmosphere, thus its surface is exposed to solar ultraviolet radiation and the solar wind. Photoemission and collection of the solar wind electrons and ions may result in lunar surface charging. On the dayside, the surface potential is mainly determined by photoelectrons, modulated by the solar wind; while the nightside surface potential is a function of the plasma distribution in the lunar wake. Taking the plasma observations in the lunar environment as inputs, the global potential distribution is calculated according to the plasma sheath theory, assuming Maxwellian distributions for the surface emitted photoelectrons and the solar wind electrons. Results show that the lunar surface potential and sheath scale length change versus the solar zenith angle, which implies that the electric field has a horizontal component in addition to the vertical one. By differentiating the potential vertically and horizontally, we obtain the global electric field. It is found that the vertical electric field component is strongest at the subsolar point,which has a magnitude of 1 V m~(-1). The horizontal component is much weaker, and mainly appears near the terminator and on the nightside, with a magnitude of several mV m~(-1). The horizontal electric field component on the nightside is rotationally symmetric around the wake axis and is strongly determined by the plasma parameters in the lunar wake.
The Moon has no significant atmosphere, thus its surface is exposed to solar ultraviolet radiation and the solar wind. Photoemission and collection of the solar wind electrons and ions may result in lunar surface charging. On the dayside, the surface potential is mainly determined by photoelectrons, modulated by the solar wind; while the nightside surface potential is a function of the plasma distribution in the lunar wake. Taking the plasma observations in the lunar environment as inputs, the global potential distribution is calculated according to the plasma sheath theory, assuming Maxwellian distributions for the surface emitted photoelectrons and the solar wind electrons. Results show that the lunar surface potential and sheath scale length change versus the solar zenith angle, which implies that the electric field has a horizontal component in addition to the vertical one. By differentiating the potential vertically and horizontally, we obtain the global electric field. It is found that the vertical electric field component is strongest at the subsolar point,which has a magnitude of 1 V m~(-1). The horizontal component is much weaker, and mainly appears near the terminator and on the nightside, with a magnitude of several mV m~(-1). The horizontal electric field component on the nightside is rotationally symmetric around the wake axis and is strongly determined by the plasma parameters in the lunar wake.
The Moon has no significant atmosphere, thus its surface is exposed to solar ultraviolet radiation and the solar wind. Photoemission and collection of the solar wind electrons and ions may result in lunar surface charging. On the dayside, the surface potential is mainly determined by photoelectrons, modulated by the solar wind; while the nightside surface potential is a function of the plasma distribution in the lunar wake. Taking the plasma observations in the lunar environment as inputs, the global potential distribution is calculated according to the plasma sheath theory, assuming Maxwellian distributions for the surface emitted photoelectrons and the solar wind electrons. Results show that the lunar surface potential and sheath scale length change versus the solar zenith angle, which implies that the electric field has a horizontal component in addition to the vertical one. By differentiating the potential vertically and horizontally, we obtain the global electric field. It is found that the vertical electric field component is strongest at the subsolar point,which has a magnitude of 1 V m~(-1). The horizontal component is much weaker, and mainly appears near the terminator and on the nightside, with a magnitude of several mV m~(-1). The horizontal electric field component on the nightside is rotationally symmetric around the wake axis and is strongly determined by the plasma parameters in the lunar wake.
引文
Anuar,A.K.,Honary,F.,Hapgood,M.,&Roussel,J.-F.2013,Journal of Geophysical Research(Space Physics),118,6723
Borisov,N.,&Mall,U.2002,Journal of Plasma Physics,67,277
Freeman,J.W.,&Ibrahim,M.1975,Moon,14,103
Halekas,J.S.,Mitchell,D.L.,Lin,R.P.,et al.2002,Geophys.Res.Lett.,29,1435
Halekas,J.S.,Lin,R.P.,&Mitchell,D.L.2003,Geophys.Res.Lett.,30,2117
Halekas,J.S.,Bale,S.D.,Mitchell,D.L.,&Lin,R.P.2005,Journal of Geophysical Research(Space Physics),110,A07222
Lei,L.,Zhang,Y.T.,Zhou,B.,&Feng,Y.Y.2016,Science China Earth Sciences,59,2053
Manka,R.H.1973,in Astrophysics and Space Science Library,37,Photon and Particle Interactions with Surfaces in Space,ed.R.J.L.Grard,347
Nishino,M.N.,Fujimoto,M.,Maezawa,K.,et al.2009,Geophys.Res.Lett.,36,L16103
Nitter,T.,Havnes,O.,&Melands?,F.1998,J.Geophys.Res.,103,6605
Poppe,A.,&Hor′anyi,M.2010,Journal of Geophysical Research(Space Physics),115,A08106
Riemann,K.-U.1991,Journal of Physics D Applied Physics,24,493
Saito,Y.,Yokota,S.,Tanaka,T.,et al.2008,Geophys.Res.Lett.,35,L24205
Saito,Y.,Nishino,M.N.,Fujimoto,M.,et al.2012,Earth,Planets,and Space,64,83
Wang,X.-D.,Bian,W.,Wang,J.-S.,et al.2010,Geophys.Res.Lett.,37,L07203
Whipple,E.C.1981,Reports on Progress in Physics,44,1197
Xie,L.,Li,L.,Zhang,Y.,et al.2015,Journal of Geophysical Research(Space Physics),120,6559
Ye,Q.M.,2010,Master Thesis,Central University,Taibei
Borisov,N.,&Mall,U.2002,Journal of Plasma Physics,67,277
Freeman,J.W.,&Ibrahim,M.1975,Moon,14,103
Halekas,J.S.,Mitchell,D.L.,Lin,R.P.,et al.2002,Geophys.Res.Lett.,29,1435
Halekas,J.S.,Lin,R.P.,&Mitchell,D.L.2003,Geophys.Res.Lett.,30,2117
Halekas,J.S.,Bale,S.D.,Mitchell,D.L.,&Lin,R.P.2005,Journal of Geophysical Research(Space Physics),110,A07222
Lei,L.,Zhang,Y.T.,Zhou,B.,&Feng,Y.Y.2016,Science China Earth Sciences,59,2053
Manka,R.H.1973,in Astrophysics and Space Science Library,37,Photon and Particle Interactions with Surfaces in Space,ed.R.J.L.Grard,347
Nishino,M.N.,Fujimoto,M.,Maezawa,K.,et al.2009,Geophys.Res.Lett.,36,L16103
Nitter,T.,Havnes,O.,&Melands?,F.1998,J.Geophys.Res.,103,6605
Poppe,A.,&Hor′anyi,M.2010,Journal of Geophysical Research(Space Physics),115,A08106
Riemann,K.-U.1991,Journal of Physics D Applied Physics,24,493
Saito,Y.,Yokota,S.,Tanaka,T.,et al.2008,Geophys.Res.Lett.,35,L24205
Saito,Y.,Nishino,M.N.,Fujimoto,M.,et al.2012,Earth,Planets,and Space,64,83
Wang,X.-D.,Bian,W.,Wang,J.-S.,et al.2010,Geophys.Res.Lett.,37,L07203
Whipple,E.C.1981,Reports on Progress in Physics,44,1197
Xie,L.,Li,L.,Zhang,Y.,et al.2015,Journal of Geophysical Research(Space Physics),120,6559
Ye,Q.M.,2010,Master Thesis,Central University,Taibei