"神舟"五号的空间环境保障

空间环境安全保障是载人航天器飞行安全和航天员生命安全保障的一个重要部分．文章从高层大气、高能辐射环境、流星体空间碎片和重大空间环境扰动事件等四个方面空间环境要素对载人航天的影响，介绍了空间环境预报中心为“神舟”五号载人飞行任务所作的空间环境保障工作．     

Effects of Perpendicular Thermal Velocities on the Transverse Instability in Electron Phase Space Holes

A multi-dimensional electron phase-space hole （electron hole） is considered to be unstable to the transverse instability. We perform two-dimensional （2D） particle-in-cell （PIC） simulations to study the evolutions of electron holes in weakly magnetized plasma （Ωe〈 Wpe, where Ωe and Wpe are the electron gyrofrequency and plasma frequency, respectively）, and the effects of perpendicular thermal velocities on the transverse instability are investigated. The transverse instability can cause decay of the electron holes. We find that with the increasing perpendicular thermal velocity tending to stabilize the transverse instability, the corresponding wave numbers decrease.