Ionospheric electron content and space weather: Some examples

Space Weather effects influence the atmosphere of the Earth, among others s tratospheric ozone. One other region of the upper atmosphere which shows ve ry strong Space Weather dependence is the ionosphere. It is a very importan t region because it affects satellite communication and navigation. On the other hand the ionization is a good tracer and indicator for various Space Weather influences. In this respect the ionosphere has no predictive capabi lities and cannot support early warning but it provides one link between th e sun, the solar wind, the magnetosphere and the neutral atmosphere. Solar EUV induced inospheric effects are coupled to solar radiation related event s in the neutral atmosphere and therefore ionospheric effects give some qua litative hints at possible effects on stratospheric ozone. Ionospheric Spac e Weather effects can be observed continously from the ground by means of p ropagation effects on radio waves. Electron content (TEC) is a very importa nt descriptive quantity for the ionosphere of the Earth. TEC is gained by m eans of "propagation effects" which are observed on received radio signals which are transmitted from artificial satellites. TEC data have been collec ted in Europe systematically and on a longterm basis since 1965. The data a re used to investigate "geophysical events", e.g., the Space Weather relate d (magnetic) storm effects. They are also used to formulate empirical model s which describe the large scale and longterm behaviour of average TEC data , usually of monthly medians. We show examples for "instantaneous" TEC data , for a monthly median TEC model and for TEC maps produced on a regular bas is for application purposes. (C) 2000 Elsevier Science Ltd. All rights rese rved.