Ionization of the AtmosphereThe electrical nature of the atmosphere arises from space charges carried by free electrons and ions which are maintained by an aerochemical balance of ionizations, loss processes and dynamical motions of the atmospheric gas. In the regions of the troposphere and the stratosphere, ions plays an important role in atmospheric electricity. Large ions -charged nuclei-dominate in the lower atmosphere below a few kilometers in altitudes, which are mainly composed of water droplets, clusters of gas molecules and aerosols.Charges are generated by turbulent collisions of water droplets in thunderstorm clouds and ionization by the radioactivity. A small part of them is also caused by ionization due to volcanic activities and artificially produced pollutions. On the other hand, small ions of atmospheric gas molecules and of submicron aerosols are produced by cosmic ray bombardments and subsequent ion attachment processes. They are distributed in the altitude range below 50 km, with a broad maximum of ion concentration around 20 km. A temporal ionization is expected locally at an extensive air-shower due to the entry of very high energy cosmic rays (nf>103 cm-3, in the core of a large extensive air-shower).In the atmosphere above 70 km the solar radiation is the major source for ionization, and the concentration of electrons becomes appreciable, because of the increasing flux of ionizing agencies and also because of the long life of electrons due to the prevailing condition of extremely low air density. The ionization due to meteoric impacts is appreciable in the lower ionosphere. However, meteoric dust particles precipitating upon the atmosphere,