无线电波传播第三讲近地空间电离层传播模式.PPT

* * * * * * * * * * * * The Van Allen radiation belt is a torus comprising two layers of energetic charged particles (plasma) around Earth, which is held in place by Earths magnetic field. The torus extends from an altitude of about 1,000 to 60,000 kilometres above the Earths surface, in which region radiation levels vary. It is thought that most of the particles that form the belts come from solar wind, and other particles by cosmic rays.[1] It is named after its discoverer, James Van Allen, and is located in the inner region of the Earths magnetosphere. It is split into two distinct belts, with energetic electrons forming the outer belt and a combination of protons and electrons forming the inner belt. In addition, the radiation belts contain lesser amounts of other nuclei, such as alpha particles. The belts pose a hazard to satellites, which must protect their sensitive components with adequate shielding if their orbit spends significant time in the radiation belts. The Van Allen radiation belt is a torus comprising two layers of energetic charged particles (plasma) around Earth, which is held in place by Earths magnetic field. The torus extends from an altitude of about 1,000 to 60,000 kilometres above the Earths surface, in which region radiation levels vary. It is thought that most of the particles that form the belts come from solar wind, and other particles by cosmic rays.[1] It is named after its discoverer, James Van Allen, and is located in the inner region of the Earths magnetosphere. It is split into two distinct belts, with energetic electrons forming the outer belt and a combination of protons and electrons forming the inner belt. In addition, the radiation belts contain lesser amounts of other nuclei, such as alpha particles. The belts pose a hazard to satellites, which must protect their sensitive components with adequate shielding if their orbit spends significant time in the radiation belts. * * * * * * * * * * * * * * * * * * * * * * The hydroge