• ISSN 2097-1893
    • CN 10-1855/P

    月球带电粒子环境综述

    Review of the lunar charged particle environment

    • 摘要: 带电粒子是月球空间环境的主要要素之一. 它们的来源、成分与能量分布较为复杂,其空间分布及动态变化又与较小尺度的电磁场结构耦合,使得月球空间环境迥异于具有宏大磁场的地球或行星. 相比地球,对月球空间环境的探测手段相对单一,探测频次也较低,特别是对月面及20 km高度以下空间的就位探测极少,这都导致对月球空间带电粒子的起源、浓度、动态及其可能的空间效应和危害的理解并不全面. 本文尽可能多地收集并系统性整理了自阿波罗时代以来人类探测月球带电粒子的研究成果,试图展示当前的探测研究的脉络. 由于对地外空间的认识强烈依赖各个国家深空探测项目的实施,因此,首先对各国的探月任务、载荷和科学目标进行罗列,以期展示人类探月兴趣点的变迁. 由于月面电磁场与带电粒子之间难以分割的耦合关系,本文随后对月球电磁场的现有认识做介绍. 对月球带电粒子环境综述的主体部分,以“月球轨道背景空间环境与月球相互作用”和“月球空间带电粒子种类”为两条主线,对探测研究成果进行系统性梳理. 可以看到有些探测和理论之间,甚至是不同的探测结果之间,都存在很大差别,甚至相互矛盾. 这些不确定性可能正是未来探测研究需要关注的方向.

       

      Abstract: Charged particles constitute one of the essential physical elements within the lunar space environment. Their origins, compositions and energy spectra are remarkably complex, and their spatial distribution and temporal dynamics are intricately coupled with localized electromagnetic field structures, rendering the lunar space environment fundamentally distinct from that of Earth or other magnetized planetary bodies. Compared to Earth, our methods for probing the lunar space environment remain relatively limited, both in terms of observational techniques and detection frequency. Notably, in situ measurements within the critical region encompassing the lunar surface and the low-altitude zone below 20 kilometers are exceptionally sparse. These observational gaps have collectively led to a fragmented and incomplete understanding of the fundamental characteristics of lunar charged particles, including their genesis, density fluctuations, dynamic behavior, as well as their potential spatial effects and associated hazards for exploration infrastructure and human activity. This review aims to synthesize and systematically organize the research findings from observations of lunar charged particles dating back to the Apollo era, endeavoring to present a coherent picture of the current state of knowledge and the trajectory of exploration. Recognizing that our comprehension of extraterrestrial space is profoundly shaped by the execution of national and international deep-space exploration programs, Section 1 begins by cataloging the key lunar missions undertaken by various nations, along with their primary scientific payloads and objectives. This historical overview is intended to illustrate the shifting priorities and evolving interests in lunar exploration over the decades. Given the inextricable coupling between charged particles and ambient electromagnetic fields, Section 2 provides a concise summary of the current understanding of lunar electromagnetic fields, encompassing both crustal magnetic anomalies and global fields, either transiently induced or permenantly intrinsic. The core of this review is structured along two parallel analytical threads. The first, covered in Sections 3 through 5, focuses on the "Background space environment along lunar orbit and its interactions with the Moon." This part examines the solar wind and geomagnetospheric plasma populations as they encounter and interact with the Moon, leading to phenomena such as absorption, reflection, and the formation of wake structures. The second thread, spanning Sections 6 to 11, is organized by "Types of charged particles in lunar space." Here, we systematically review observational results and theoretical models pertaining to specific particle populations, including photoelectrons, secondary electrons, exospheric neutrals, lunar dust, high-energy rays, and particles generated by human activities. Throughout this synthesis, it becomes evident that significant discrepancies and even outright contradictions exist, not only between theoretical predictions and observational data but also among different observational datasets themselves. These inconsistencies highlight the challenges inherent in remote and in situ space physics measurements and point to critical gaps in our current knowledge. Such uncertainties and unresolved questions likely define the most promising and necessary directions for future targeted investigations, requiring more advanced instrumentation, coordinated multi-point measurements, and sustained observation campaigns to unravel the complex electrodynamic environment of our closest celestial neighbor.

       

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