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辐射带 1958年:探险者一号、探险者三号和苏联的卫星三号等科学卫星被发射后科学家出乎意料地发现了地球周围强烈的、被地磁场束缚的范艾伦辐射带（内辐射带）。 这个辐射带由能量在10至100MeV的质子组成，这些质子是由于宇宙线与地球大气上层撞击导致的中子衰变产生的，其中心在赤道离地球中心约1.5地球半径。 后来人们发现在离地球中心2.5至8个地球半径的地方还有一层被地磁场束缚的离子和电子。这些等离子中能量比较高的（约1MeV）被称为外辐射带，而其主要组成部分则能量比较低（在65keV左右），这些等离子组成环电流等离子。
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James Van Allen TIME magazine Man of the Year in 1960
(September 7, 1914 – August 9, 2006) an American space scientist at the University of Iowa. The Van Allen radiation belts were named after him, following the 1958 satellite missions (Explorer 1 and Explorer 3) in which Van Allen had argued that a Geiger counter should be used to detect charged particles. James Van Allen TIME magazine Man of the Year in 1960
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一部分进入地球磁层，或者说被地球磁层俘获的高能粒子，则被禁锢在两个被称为辐射带的范围内。这两个辐射带是物理学家范·艾伦（Van Allen）于 1959年通过人造卫星的实验发现的，故被命名为范·艾伦辐射带。它分内外两带：内辐射带高度在1—2个地球半径之间，宽约5000km，范围限于南北磁纬40°之间，所观测到的主要是高能质子；外辐射带的高度约为3—4个地球半径，其纬度范围为南北磁纬50°一60°之间，所观测到的主要是高能电子。辐射带的范围和形状，受地球磁场的制约，并且因太阳活动而变化。至于这些粒子是如何陷在这二个区域里，其详细物理过程尚未清楚。
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辐射带 被束缚在磁场中的离子可以非常稳定，尤其内辐射带的离子非常稳定，这里的粒子可以维持数年之久。比如1962年7月美国在这个层里爆炸了一枚氢弹，其导致的人工的高能电子带在四五年后依然存在。 外辐射带和环电流不稳定，原因是其粒子与地冕中的粒子的碰撞使得它们不断丧失。这说明在这里有一个不断产生新的等离子的机理。
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范艾伦辐射带，指在地球附近的近层宇宙空间中包围着地球的高能辐射层，由美国物理学家詹姆斯·范·艾伦发现并以他的名字命名。范艾伦辐射带分为内外两层，内外层之间存在范艾伦带缝，缝中辐射很少。范艾伦辐射带将地球包围在中间。 发现 1958年1月31日，美国第一颗人造卫星探险者一号升空，当升至800千米高空时，星上所载盖革计数器读数突然下降至0。到1958年3月26日探险者三号升空时，又发生了同样的情况。范艾伦认为，这是因为存在极大量的辐射导致计数器达到饱和而失灵造成的。因此，同年7月26日发射探险者四号时，他在计数器前端加入一小片薄铅以阻挡部分辐射。果然，新的卫星证实了他的猜测。 成因及影响 20世纪初，挪威空间物理学家斯托默就从理论上证明，地球周围存在一个带电粒子捕获区。它是由地球磁场俘获太阳风中的带电粒子所形成的。一般来说，内辐射带里高能质子多，外辐射带里高能电子多。辐射带会对人类身体造成巨大伤害，因此，它是人类进行星际转移的巨大障碍。 其他影响 影响哈伯望远镜的观测，因为哈伯处在相当低的轨道，离地仅559公里来运行。因此，当哈伯通过南大西洋上空时必须暂时关闭观测。因为范艾伦幅射带刚好在这里碰触到地球的上层大气，如果开启观测的话，可能会损坏哈伯的观测元件。
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Outer belt The large outer radiation belt extends from an altitude of about three to ten Earth radii (RE) or 13,000 to 60,000 kilometres above the Earth's surface. Its greatest intensity is usually around 4–5 RE. The outer electron radiation belt is mostly produced by the inward radial diffusion[5][6] and local acceleration[7] due to transfer of energy from whistler mode plasma waves to radiation belt electrons. Radiation belt electrons are also constantly removed by collisions with atmospheric neutrals,[7] losses to magnetopause, and the outward radial diffusion. The outer belt consists mainly of high energy (0.1–10 MeV) electrons trapped by the Earth's magnetosphere. The gyroradii for energetic protons would be large enough to bring them into contact with the Earth's atmosphere. The electrons here have a high flux and at the outer edge (close to the magnetopause), where geomagnetic field lines open into the geomagnetic "tail", fluxes of energetic electrons can drop to the low interplanetary levels within about 100 km (a decrease by a factor of 1,000). The trapped particle population of the outer belt is varied, containing electrons and various ions. Most of the ions are in the form of energetic protons, but a certain percentage are alpha particles and O+ oxygen ions, similar to those in the ionosphere but much more energetic. This mixture of ions suggests that ring current particles probably come from more than one source. The outer belt is larger than the inner belt and its particle population fluctuates widely. Energetic (radiation) particle fluxes can increase and decrease dramatically as a consequence of geomagnetic storms, which are themselves triggered by magnetic field and plasma disturbances produced by the Sun. The increases are due to storm-related injections and acceleration of particles from the tail of the magnetosphere.
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Inner belt The inner Van Allen Belt extends from an altitude of 100–10,000 km[8] (0.01 to 1.5 Earth radii) above the Earth's surface, and contains high concentrations of energetic protons with energies exceeding 100 MeV and electrons in the range of hundreds of keV, trapped by the strong (relative to the outer belts) magnetic fields in the region. It is believed that protons of energies exceeding 50 MeV in the lower belts at lower altitudes are the result of the beta decay of neutrons created by cosmic ray collisions with nuclei of the upper atmosphere. The source of lower energy protons is believed to be proton diffusion due to changes in the magnetic field during geomagnetic storms.[
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