Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era
Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era
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DOI：
10.1029/2018ja025940
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发表时间：
2019-11-28
影响因子：
2.8
通讯作者：
Hudson, M. K.
中科院分区：
文献类型：
--
作者：
Li, W.;Hudson, M. K.
1958年，探测器1号上的仪器发现了地球的范艾伦辐射带，这是太空时代的第一个重大发现。对捕获的巨电子伏（MeV）粒子（主要是低空的质子和高空的电子）不同的内外区的观察，导致了源和损失机制的早期模型，包括内区质子的宇宙射线反照率中子衰变，外区电子的径向扩散以及由于俯仰角散射而对大气的损失。这种散射降低了粒子在与地球磁场平行的反弹运动中的镜像高度，直到它们遭受碰撞损失。1989-1991年第22太阳活动周期的观测修正了辐射带是不同来源的高能粒子的准静态内外带的观点。1990年7月发射的联合辐射释放和效应卫星测量了外区电子的动态变化。这种变化是由不同类型的日球层结构引起的，这些结构随着太阳周期的变化而变化。2012年8月发射的双范艾伦探测器在第24太阳周期的衰退期提供了更长、更全面的测量。大约一半的中等地磁风暴，由环电流的强度决定，主要由数百千电子伏特的质子携带，在外层区域产生被捕获的相对论性电子通量的增加。本文叙述了储存在磁层尾区的数百电子伏特的电子加速到捕获区的mevenies的机制：磁层波驱动的提示和扩散径向输运和局部加速。这样的波也会产生俯仰角散射损失，向外径向输运也是如此，当磁层被压缩时，这种损失会增强。虽然准线性模拟已被用于成功地再现辐射带粒子动力学的许多基本特征，但非线性波粒相互作用被发现对引起更快速的粒子加速或降水具有潜在的重要意义。范艾伦辐射带的基础物理学发现可能为理解太阳系中其他磁化行星的高能粒子动力学，整个宇宙的系外行星，以及天体物理学和实验室等离子体提供了见解。计算辐射带模型有了显著的改进，特别是在范艾伦探测器时代，辐射带状态的同化预测变得更加可行。此外，机器学习技术已经发展到指定和预测范艾伦辐射带的状态。鉴于辐射带变率对技术系统的潜在空间天气影响，预计这些新的辐射带模式将在未来的技术社会中发挥关键作用，就像今天的气象模式一样。
Discovery of the Earth's Van Allen radiation belts by instruments flown on Explorer 1 in 1958 was the first major discovery of the Space Age. The observation of distinct inner and outer zones of trapped megaelectron volt (MeV) particles, primarily protons at low altitude and electrons at high altitude, led to early models for source and loss mechanisms including Cosmic Ray Albedo Neutron Decay for inner zone protons, radial diffusion for outer zone electrons and loss to the atmosphere due to pitch angle scattering. This scattering lowers the mirror altitude for particles in their bounce motion parallel to the Earth's magnetic field until they suffer collisional loss. A view of the belts as quasi-static inner and outer zones of energetic particles with different sources was modified by observations made during the Solar Cycle 22 maximum in solar activity over 1989-1991. The dynamic variability of outer zone electrons was measured by the Combined Radiation Release and Effects Satellite launched in July 1990. This variability is caused by distinct types of heliospheric structure that vary with the solar cycle. The launch of the twin Van Allen Probes in August 2012 has provided much longer and more comprehensive measurements during the declining phase of Solar Cycle 24. Roughly half of moderate geomagnetic storms, determined by intensity of the ring current carried mostly by protons at hundreds of kiloelectron volts, produce an increase in trapped relativistic electron flux in the outer zone. Mechanisms for accelerating electrons of hundreds of electron volts stored in the tail region of the magnetosphere to MeVenergies in the trapping region are described in this review: prompt and diffusive radial transport and local acceleration driven by magnetospheric waves. Such waves also produce pitch angle scattering loss, as does outward radial transport, enhanced when the magnetosphere is compressed. While quasilinear simulations have been used to successfully reproduce many essential features of the radiation belt particle dynamics, nonlinear wave-particle interactions are found to be potentially important for causing more rapid particle acceleration or precipitation. The findings on the fundamental physics of the Van Allen radiation belts potentially provide insights into understanding energetic particle dynamics at other magnetized planets in the solar system, exoplanets throughout the universe, and in astrophysical and laboratory plasmas. Computational radiation belt models have improved dramatically, particularly in the Van Allen Probes era, and assimilative forecasting of the state of the radiation belts has become more feasible. Moreover, machine learning techniques have been developed to specify and predict the state of the Van Allen radiation belts. Given the potential Space Weather impact of radiation belt variability on technological systems, these new radiation belt models are expected to play a critical role in our technological society in the future as much as meteorological models do today.