Astroparticle Physics

142 7 Secondary Cosmic RaysFig. 7.3(a) Relation between atmosphericdepth (column density) andpressure(b) column density of theatmosphere as a function ofaltitude up to 28 kmradiation beltssities of protons and electrons in the Van Allen belts. Theproton belt extends over altitudes from 2 000 to 15 000 km.It contains particles with intensities up to 10 8 /(cm 2 s) andenergies up to 1 GeV. The electron belt consists of two parts.The inner electron belt with flux densities of up to 10 9particles per cm 2 and s is at an altitude of approximately3 000 km, while the outer belt extends from about 15 000 kmto 25 000 km. The inner part of the radiation belts is symmetricallydistributed around the Earth while the outer partis subject to the influence of the solar wind and consequentlydeformed by it (see also Fig. 1.9 and Fig. 1.13).7.1 Propagation in the Atmosphere“Astroparticles are messengers fromdifferent worlds.”Anonymousinteraction in the atmospherecolumn densityPrimary cosmic rays are strongly modified by interactionswith atomic nuclei in the atmospheric air. The columndensity of the atmosphere amounts to approximately 1000g/cm 2 , corresponding to the atmospheric pressure of about1000 hPa. Figure 7.3 (a) shows the relation between columndensity, altitude in the atmosphere, and pressure. Figure 7.3(b) shows this relation in somewhat more detail for altitudesbelow 28 km. The residual atmosphere for flight altitudes