A method for characterizing a state of a planetary atmosphere or of a part of the atmosphere, especially of the ionosphere of the earth includes determining values of an ionization state, especially of an electron density and/or of an electron content, in the atmosphere or in the part of the atmosphere as a function of a location variable and as a function of a time variable and determining at least one characteristic quantity for the atmosphere or the part of the atmosphere. The characteristic quantity is determined on the basis of the values of the ionization state found for the atmosphere or the part of the atmosphere.