This paper presents the statistical analysis of the diurnal variations of the F layer at the equatorial station of Ouagadougou (Lat: 12.4 N; Long: 358.5 E; dip: 5.9 ) from 1966 to 1998 (=> ~11 680 days). We consider three main factors of variability: (1) the season (spring, summer, autumn and winter), (2) the phase of the sunspot cycle (ascending, maximum, descending and minimum) and (3) the ge...

For a long time, the equivalent ionospheric slab thickness ? has remained in shadow of main parameters: maximum density, NmF2 (or critical frequency, foF2), and total electron content. Empirical global models have been developed for these two parameters. Recently, several appeared concurrently. This paper compares Neustrelitz model (NSTM), with ?(IRI-Plas) IRI-Plas model, ?(Appr) approximation ...

On 20 September 1999 UT (21 September in local time, LT) a large earthquake Mw=7.7 struck central Taiwan near the small town of Chi-Chi. The greatest plasma frequency in the ionosphere, foF2, observed by the ChungLi ionosonde (25.0N, 121.2E) reveals three clear precursors at 1, 3, and 4 days prior to the earthquake. This paper examines the ionospheric total electron content (TEC) observed by a ...

The relative contributions of quasi-periodic oscillations from 2 to 35 days to the variability of foF2 at middle northern latitudes between 42°N and 60°N are investigated. The foF2 hourly data for the whole solar cycle 21 (1976±1986) for four European ionospheric stations Rome (41.9°N, 12.5°E), Poitiers (46.5°N, 0.3°E), Kaliningrad (54.7°N, 20.6°E) and Uppsala (59.8°N, 17.6°E) are used for anal...

This paper presents a comparison of the International Reference Ionosphere (IRI-2007) model over the eastern Mediterranean region with peak ionospheric characteristics (foF2-hmF2) and electron density profiles measured by FORMOSAT-3/COSMIC satellites in terms of GPS radio occultation technique and the Cyprus digisonde. In the absence of systematic ionosonde measurements over this area, COSMIC m...

Moderate ionospheric disturbances combined with storm signatures are characterized by the positive index (WU), negative (WL), and range (WE = WU – WL). We assign weights to these indices as a function of magnitude W-index, observation latitude critical frequency F2 layer, foF2 (the layer peak electron density, NmF2) or total content (TEC). It is shown that moderate irregularities (W ±2) occur m...

Using a method suggested by the authors earlier, the long-term trends of the F2-layer critical frequency, foF2 are derived for a set of ionospheric stations with a wide latitudinal and longitudinal coverage. All the trends are found to be negative. A pronounced dependence on geomagnetic latitude is found, the trend magnitude increasing with the latter. No globe scale longitudinal e€ect in trend...

Prediction of ionospheric parameters, such as F2 layer critical frequency (foF2) at low latitude regions is significant interest in understanding variation effects on high-frequency communication and global navigation satellite system. Currently, deep learning algorithms have made a striking accomplishment capturing variability. In this paper, we use the state-of-the-art hybrid neural network c...