繼日本近年的探月計畫-KAGUYA首次發現少量的太陽風粒子能夠從月球表面反射出來後，我利用單一粒子模擬計算太陽風質子與月球日側半球的交互作用。計算結果發現在距離月球表面一百公里高的球層，反射質子的分佈呈現明顯的南北與東西向不對稱性，這是因為質子從表面反射後受到電場加速，而具有相當大的迴旋半徑，並且其移動方向又受到行星際間磁場和電場的方向所影響。計算結果也指出，反射質子在接近月球表面的區域就能被行星際間電場加速到高速，我們稱之為Self-pickup過程。在特定的行星際磁場強度下，從表面反射出來的質子有機會進入月球的夜側半球，這是個以往被認為缺乏太陽風質子的空腔區域。

Following the first discovery of reflected solar wind protons from the lunar surface by KAGUYA experimental team, I study the motion of the solar wind protons which are reflected from the lunar dayside hemisphere by using single particle trajectory calculations in a Monte-Carlo simulation. The global distribution of these reflected protons at 100 km altitude above the lunar surface shows strong asymmetry in north-south and dawn-dusk directions because of their large gyroradii and the directions of the accelerating electric field and the interplanetary magnetic field. The reflected protons could be accelerated to high speed in near-surface region because of the self-pickup process. Under certain condition of the interplanetary magnetic field, a portion of them can reach the shadow region which is usually considered to be devoid of solar wind protons.

Fa, W., and Y. -Q. Jin (2007), Quantitative estimation of helium-3 spatial distribution in the lunar regolith layer, Icarus, 190, 15-23.
Freeman, J. W., and M. Ibrahim (1975), Lunar electric fields, surface potential and associated plasma sheaths, Earth Moon Planets, 14, 103–114.
Grobman, W. D. and J. L. Blank (1969), Electrostatic Potential Distribution of the Sunlit Lunar Surface, J. of Geophys. Res. Space Physics, 74, 16.
Halekas, J. S., D. L. Mitchell, R. P. Lin, L. L. Hood, M. H. Acuna, and A. B. Binder (2002), Evidence for negative charging of the lunar surface in shadow, Geophys. Res. Lett., 29, 77.
Halekas, J. S., R. P. Lin, and D. L. Mitchell (2005), Large negative lunar surface potentials in sunlight and shadow, Geophys. Res. Lett., 32, L09102.
Halekas, J. S., G. T. Delory, D. A. Brain, R. P. Lin, D. L. Mitchell (2008a), Density cavity observed over a strong lunar crustal magnetic anomaly in the solar wind: A mini-magnetosphere?, Planet. Space Sci., 56, 941-946.
Halekas, J. S., G. T. Delory, R. P. Lin, T. J. Stubbs, and W. M. Farrell (2008b), Lunar Prospector observations of the electrostatic potential of the lunar surface and its response to incident currents, J. of Geophys. Res., 113, A09102.
Harnett, E. M., and Robert Winglee (2000), Two-dimensional MHD simulation of the solar wind interaction with magnetic field anomalies on the surface of the Moon, J. of Geophys. Res., 105, 24997.
Harnett, E. M., and R. M. Winglee (2003), 2.5-D fluid simulations of the solar wind interacting with multiple dipoles on the surface of the Moon, J. of Geophys. Res., 108, 1088.
Lin, R. P., K. A. Anderson, and L. L. Hood (1988), Lunar surface magnetic field concentrations antipodal to young large impact basins, Icarus, 74, 529.
Lyon, E. F., H. S. Bridge, and J. H. Binsack (1967), Explorer 35 plasma measurements in the vicinity of the Moon, J. Geophys Res., 72, 6113– 6117.
Martin Wieser, Stas Barabash, Yoshifumi Futaana, Mats Holmstrom, Anil Bhardwaj, R Sridharan, M B Dhanya, Peter Wurz, Audrey Schaufelberger, Kazushi Asamura (2009), Extremely high reflection of solar wind protons as neutral hydrogen atoms from regolith in space, Planet. Space Sci., 57, 2132-2134.
Mendis, A., J. R. Hill, H. L. F. Houpis, and E. C. Whipple (1988), On the electrostatic charging of the cometary nucleus, Astrophys. J., 249, 787.
Mitchell, D.L., Halekas, J.S., Lin, R.P., Frey, S., Hood, L.L., Acuna, M.H., and Binder, A., (2008). Global mapping of Lunar crustal magnetic fields by Lunar Prospector. Icarus 194, 401–409.
Nishino, M. N., K. Maezawa, M. Fujimoto, Y. Saito, S. Yotoka, K. Asamura, T. Tanaka, H. Tsunakawa, M. Matsushima, F. Takahashi, T. Terasawa, H. Shibuya, and H. Shimizu (2009a), Pairwise energy gain-loss feature of solar wind protons in the near-Moon wake, Geophys. Res. Lett., 36, 12108.
Nishino, M. N., et al. (2009b), Solar‐wind proton access deep into the near‐ Moon wake, Geophys. Res. Lett., 36, 16103.
Ogilvie, K. W., J. T. Steinberg, R. J. Fitzenreiter, C. J. Owen, A. J. Lazarus, W. M. Farrell, and R. B. Torbert (1996), Observations of the lunar plasma wake from the Wind spacecraft on December 27, 1994, Geophys. Res. Lett., 23(10), 1255–1258.
Saito, Y., S. Yokota, T. Tanaka, K. Asamura, M. N. Nishino, M. Fujimoto, H. Tsunakawa, H. Shibuya, M. Matsushima, H. Shimizu, F. Takahashi, T. Mukai, and T. Terasawa (2008), Solar wind proton reflection at the lunar surface: Low energy ion measurement by MAP-PACE onboard SELENE (KAGUYA), Geophys. Res. Lett., 35, 24205.
Saito, Y. (2009), Summary of the low energy ion distribution on the dayside of the Moon, Lunar Plasma Environment Science and New Advances in Lunar Selenodesy Workshop.
Stubbs, T. J., J. S. Halekas, W. M. Farrell, and R. R. Vondrak (2005), Lunar surface charging: A global perspective using Lunar Prospector data, Workshop on Dust in Planetary System 2005.
Walbridge, E. (1975), Lunar photoelectron layer dynamics, Earth Moon Planets, 14, 115-121.
Wang, X.-D, W Bian, J.-S Wang, J.-J Liu, Y.-L Zou, H.-B Zhang, C Lu, J.-Z Liu, W Zuo, Y Su, W.-B Wen, M Wang, Z.-Y Ouyang, and C.-L Li (2010), Acceleration of scattered solar wind protons at the polar terminator of the Moon: Results from Chang’E-1/SWIDs, Geophys. Res. Lett., 37, 07203.