Scale-dependent analysis of Ionosphere fluctuations

Ionosphere consists of a large complex system whose analysis is of major importance, e.g., for climatology or radio-communications. Therefore, studying its variations, usually analyzed in terms of long-term trends versus short-term fluctuations, as well as the mechanisms driving them is of importance. This contribution hence performs a scale-dependent cross-analysis of the F2-region critical frequency data, locally measured at 11 mid-latitude European stations, and 5 global solar and geomagnetic indices. It shows that such Ionospheric variations are correctly described by the superimposition of well-defined long-term cycles with highly correlated fractional Gaussian noise fluctuations. Also, it is shown that mid-latitude European stations display highly correlated variations even for short-term fluctuations and that, while the solar activity mostly drives long-term cycles, short-term fluctuations are essentially controlled by the geomagnetic activity.