A method for real-time identification and tracking of traveling ionospheric disturbances using ionosonde data: first results

Traveling Ionospheric Disturbances (TIDs) are wave-like propagating irregularities that alter the electron density environment and play an important role spreading radio signals propagating through the ionosphere. A method combining spectral analysis and cross-correlation is applied to time series of ionospheric characteristics (i.e., MUF(3000)F2 or foF2) using data of the networks of ionosondes in Europe and South Africa to estimate the period, amplitude, velocity and direction of propagation of TIDs. The method is verified using synthetic data and is validated through comparison of TID detection results made with independent observational techniques. The method provides near real time capability of detection and tracking of Large-Scale TIDs (LSTIDs), usually associated with auroral activity.Postprint (published version

Correlation between airtemperature and thunderstorm activity in Africa according to the ELF measurements in Antarctica, Arctica and Ukraine

Purpose: Search for the connection of seasonal variations in characteristics of the Earth-ionosphere global resonator with air temperature in Africa. Comparison of results obtained in Arctica, Antarctica and in the midlatitudes of the Northern Hemisphere with the surface temperature of African continent. Checking the effectiveness of the point source model for describing the seasonal change in the position of regions with the greatest thunderstorm activity. Design/methodology/approach: The method of correlation analysis of time series was used. According to the long-term monitoring of the natural noise of the extremely low frequency (ELF) range at the Ukrainian Antarctic Station (UAS), at the Low Frequency Observatory of the Institute of Radio Astronomy, National Academy of Sciences of Ukraine in Martove village (Ukraine), as well as at the SOUSY observatory (Spitsbergen), seasonal changes in the level of the first mode of Shumann resonance was restored by the activity of the African thunderstorm center. The average air temperature in the African continent over the same period was estimated according to the global network of meteorological stations. When estimating the intensity of the resonance maximum of extremely low frequency radiation, a correction has been introduced for the distance to the source of lightning discharges. Findings: The presence of a strong relationship between the surface air temperature of the equatorial and sub-equatorial regions of Africa and the intensity of the Schumann resonance generated by the African thunderstorm center is shown. It is shown that the model of an effective point source adequately describes the seasonal behavior of the African thunderstorm center. Conclusions: The developed technique can be applied at various receiving points for studying all continental thunderstorm centers. Such an approach will be useful for developing the concept of using the Schumann resonator as a “global thermometer”. Simultaneous observations in several receiving points can become promising also for estimating shorter (several days) variations in global temperature

Incoherent scatter radar observations of AGW/TID events generated by the moving solar terminator

Observations of traveling ionospheric disturbances (TIDs) associated with atmospheric gravity waves (AGWs) generated by the moving solar terminator have been made with the Millstone Hill incoherent scatter radar. Three experiments near 1995 fall equinox measured the AGW/TID velocity and direction of motion. Spectral and cross-correlation analysis of the ionospheric density observations indicates that ST-generated AGWs/TIDs were observed during each experiment, with the more-pronounced effect occurring at sunrise. The strongest oscillations in the ionospheric parameters have periods of 1.5 to 2 hours. The group and phase velocities have been determined and show that the disturbances propagate in the horizontal plane perpendicular to the terminator with the group velocity of 300-400 m s-1 that corresponds to the ST speed at ionospheric heights. The high horizontal group velocity seems to contradict the accepted theory of AGW/TID propagation and indicates a need for additional investigation.Key words. Ionosphere (wave propagation) · Meteorology and atmospheric dynamics (waves and tides)</p

Ionospheric tilt measurements: application to traveling ionospheric disturbances climatology study

Ionospheric tilt is a concept used to characterize local horizontal electron density gradients in the ionosphere using a mirror reflection model. Experimental results are presented that illustrate the validity and accuracy of such approach. Analysis of the tilt measurements collected in 2012–2014 with a digisonde at Ebro observatory (40.8°N, 0.5°E) is presented. Digisonde systems allow measuring angles of arrival of ionospherically reflected radio signals, from which the ionospheric tilts are derived. The tilts are represented in terms of North-South and East-West components. Using several years of observations, a climatological distribution of wavelike variations in the tilt records presumed to be associated with traveling ionospheric disturbances (TIDs) is established. Most of the observed TIDs have their main periods of 30 min to 1.5 hr which is rather typical for medium-scale TIDs. Summertime appears to have the most frequent occurrence of TIDs. There is a good agreement between the presence of TIDs and sporadic E layer occurrence, suggesting that some TIDs can be driven by instability in the electric field which is initiated via an interhemispheric link between the E and F regions of the ionosphere. Direction of disturbance propagation is also analyzed and compared to the modeled neutral wind. There are indications that during the daytime TIDs tend to propagate in the direction opposite to the background neutral wind. This suggests that daytime TIDs are produced by atmospheric gravity waves originating in the lower atmosphere and experiencing background wind filtering effect on their upward propagation.Postprint (published version