中文摘要：

从20世纪60年代到本世纪初，人类发射了一系列绕月飞船，对月球大气和月球电离层进行研究。科学家发现，月球电离层主要出现在向日面。在表面几百米高度范围内，由太阳辐射导致的光致电离使得月球向日面出现密度不超过10^10／m2的电离层等离子体。进一步研究表明，由于月球没有内禀磁场，月球电离层与太阳风中的行星际电场耦合在一起，时刻处在“飘动”中。电离层密度的变化与月相、当地的月表剩磁、太阳风条件、当地的月壤特性等相联系。

英文摘要：

Since late 1960s, a series of spacecrafls have been launched to detect the space environment around the Moon. The obsrvation revealed the existence of a thin layer of ionosphere around the Moon with its plasma concentrating on the dayside. The photoelectron layer, with the electron density less than 10^10/m3, extends several hundred meters above the Moon surface. Further analysis showed that, as there is no intrinsic magnetic field around the Moon, the lunar ionosphere is directly coupled to the interplanetary electric field. This causes the ion flux in the lunar ionosphere to vary from time to time. Moreover, the distribution of the density of the plasma in lunar ionosphere is related to factors such as the Moon phase, the residual magnetism on the local lunar surface, the variation of solar wind and the feature of local lunar soil.