基于平均二次电子发射系数的航天器表面起电特征分析

Analysis of spacecraft charging onset using secondary electron yield

为了进一步贴近航天器表面起电环境以得到更加可信的分析结果,针对航天器在恶劣充电环境下的表面起电问题,考虑空间等离子体双麦克斯韦分布情况,建立了基于平均二次电子发射系数的航天器表面起电阈值方程,可在入射电子能量连续分布情况下定量分析航天器表面起电特征,其中双麦分布可更好地描述磁层亚爆期间的恶劣充电环境。经过理论分析,归纳出双麦分布下的两种典型等离子体状态。通过仿真计算,得到了在两种典型等离子体状态下航天器表面电位随等离子体浓度和温度变化的特征。结果表明:电子温度越高,表面负带电电位越高,充电越严重,与此同时,双麦分布下等离子体两种电子组分的浓度比值对带电结果有重要影响。

The interaction between space plasma and spacecraft results into the onset of spacecraft surface charging and the resultant electrostatic discharging events.The computation of spacecraft surface charging is commonly accomplished using the secondary electron yield of spacecraft surface irradiated by mono-energetic electrons.To depict the charging environment more precisely and obtain more reliable computation results,focusing the spacecraft charging problem under the worst charging condition and taking into accounts the double-Maxwellian plasma distribution,the threshold equation controlling the onset charging is derived based on the averaged secondary electron yield.This equation is useful to analyze spacecraft charging under the condition of election irradiation with a continuous energy spectrum.Besides,the adoption of double-Maxwellian plasma distribution could better model the space plasma condition in the case of magnetospheric substorm.By theoretical analysis,the ambient plasma is divided into two typical situations according to the charging characteristics of spacecraft surface charging.Through simulation computation,the trend of spacecraft surface charging versus plasma parameters fluctuations is obtained for these two typical situations.Results show that higher electron temperature corresponds to more severe charging with higher negative potential;meanwhile,the density ratio of the two electron components in double-Maxwellian plasma distribution plays an important role in spacecraft surface charging.The obtained conclusions could provide useful reference for quantitative analysis of spacecraft surface severe charging events.