[en] Complete text of publication follows. Waves of different time and space scales emitted by various natural and artificial sources propagate into the upper atmosphere and influence its structure, dynamics, and composition. The spectrum of waves covers a wide range of periods from tens of seconds to days. Here, we summarize observations of short period waves that have been conducted in the Czech Republic using the continuous high frequency Doppler shift measuring system. We focus on waves emitted by natural sources. Pulsations of the geomagnetic field are one of the most common sources of ionospheric waves. We repeatedly observed short period oscillations in the F2 layer simultaneously with geomagnetic Pi2 pulsations. Waves of periods ∼1-3 min were observed simultaneously on all Doppler measuring paths. The observation in years 2005-2007 showed that meteorological activity in Central Europe is not a common source of infrasonic waves. Waves of periods ∼2-5 min occurred only in two cases of exceptionally intense meteorological activity in the troposphere. Finally, we analysed observations of wave activity during weak earthquakes that occurred in the western part of the Czech Republic in autumn 2008 (magnitude lower than M=4).

[en] Complete text of publication follows. Over the past decade neural networks (NNs) have been used extensively to model various ionospheric parameters. Using data from mid-latitude stations in South Africa to describe the variability of ionospheric parameters, such as foF2 (peak electron density), hmF2 (height of peak electron density) and TEC (Total Electron Content), this paper demonstrates how NNs can provide information about the ionospheric processes at play over these latitudes. The paper will cover the development of a number of NN based models for the prediction of various ionospheric parameters. The validation of these models will be discussed as well as the ability of the NN technique to prove the physics of the ionosphere at mid-latitudes.

[en] Complete text of publication follows. This paper will present results of the analysis of the ionospheric F layer peak parameters variability under quiet and stormy conditions over middle latitudes. The analysis was carried out using manually checked hourly foF2 and hmF2 values obtained from selected ionospheric stations of the Northern (NH) and Southern hemisphere (SH). The observations were compared with the IRI2007 model outputs. Quality of the STORM model storm-time corrections was also evaluated. Overall summary of the evaluation results for Northern hemisphere indicates the decreasing ability of the model to simulate storm-time foF2 behaviour with decreasing latitude. For Southern hemisphere an efficiency of the model corrections seems to be considerably lower and decreases with increasing latitude. In general, the quiet time hmF2 above NH middle latitudes is better represented by IRI during winter and summer months, while at SH middle latitudes the model simulates hmF2 variability more successfully during summer and equinoxes. Our results indicate an importance of knowledge of the local patterns of ionospheric variability for the development of global models.