功函数对月球表面附近尘埃充电和动力学的影响  

Effect of work function on dust charging and dynamics near lunar surface

作　　者：刘志贵 宋智颖 全荣辉[1] Liu Zhi-Gui;Song Zhi-Ying;Quan Rong-Hui(College of Astronautics,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China)

机构地区：[1]南京航空航天大学航天学院,南京210016

出　　处：《物理学报》2024年第23期242-251,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:42241148,51877111)资助的课题.

摘　　要：月球表面的带电尘埃对太空任务的顺利实施构成严重威胁,对尘埃的充电和动力学的进一步研究有助于月球探测任务的顺利实施.本文研究了具有不同功函数的尘埃颗粒在月球表面的充电和动力学.重新计算了与4种尘埃颗粒功函数相关的表面充电电流,并得到了它们在不同太阳天顶角下的充电和动力学结果,揭示了尘埃颗粒充电和动力学结果对功函数的依赖性.结果显示具有较小功函数的尘埃颗粒能够达到较大的平衡态,且需要更长时间才能达到这些平衡态,其中包括尘埃颗粒能够稳定悬浮的平衡高度,能够携带的表面电荷量以及流经尘埃颗粒表面的充电电流.结果表明,当太阳天顶角在0°—90°范围内变化时,平衡态与功函数之间都呈现明显的反比关系.尘埃颗粒在临界太阳天顶角下不能发生稳定悬浮,且该角度的大小与功函数也呈反比关系.Charged dust on the lunar surface poses a threat to space missions.Research into charged dust is essential for the safety of future space missions.When calculating the charging currents related to photoelectrons,a single constant work function is assumed in the conventional lunar dust charging theory.However,the components of lunar regolith exhibit considerable diversity,including plagioclase,pyroxene,and ilmenite.Because the ability of the lunar surface or lunar dust to emit photoelectrons strongly depends on its work function,it is necessary to analyze the effect of the work function on dust charging and dynamics near the lunar surface.In this work,we use a novel method that can predict the photoelectric yield of materials with different work functions to recalculate the surface charging currents of four types of dust particles and derive their subsequent charging and dynamic results at different solar zenith angles(SZAs).As SZA varies from 0°to 90°,the work function value of dust decreases into 6 eV(Apollo lunar soil),5.58 eV(plagioclase),5.14 eV(pyroxene),and 4.29 eV(ilmenite),correspondingly.With each decrement in work function,the equilibrium charging current of dust particles increases about 0.25 times,the equilibrium charge number increases about 120–170 elemental charges,and the equilibrium height increases about 0.3–2 m.It is found that dust particles cannot levitate stably at a critical SZA,and the critical SZAs for the four types of dust particles are 28°,76°,85.8°,and 89.6°,respectively(arranged in decreasing order of work functions).These results indicate that the equilibrium heights,equilibrium currents,and critical SZAs all have an inverse relationship with the work function of dust particles as the SZA varies from 0°to 90°.Furthermore,a higher photoelectron density in areas with lower work functions leads energy losses to decrease,thus causing dust particles to take longer time to reach equilibrium.This means that the equilibrium time follows the pattern similar to that of the work fu

关 键 词：月球 悬浮尘埃 功函数 

分 类 号：P184[天文地球—天文学] V476.3[航空宇航科学与技术—飞行器设计]