Observations of quiet-time moderate midlatitude L-band scintillation in association with plasma bubbles

Observations of moderate night time amplitude scintillation on the GPS L1C/A signal were recorded at the midlatitude station of Nicosia, corresponding geographic latitude and longitude of 35.18˚N and 33.38˚E respectively, on a geomagnetically quiet day. The variations of slant total electron content (STEC) and amplitude scintillation index (S4) on the night of June 12, 2014, indicate the presence of electron density depletions accompanying scintillation occurrence. The estimated apparent horizontal drift velocity and propagation direction of the plasma depletions are consistent with those observed for the equatorial plasma bubbles, thus suggesting that the moderate amplitude L-band scintillation observed over Nicosia may be associated with the extension of such plasma bubbles. The L-band scintillation occurrence was concurrent with the observations of range spread F on the ionograms recorded by the digisonde at Nicosia. The height–time–intensity plot generated using the ionogram data also showed features which can be attributed to off-angle reflections from electron density depletions, thus corroborating the STEC observations. This observation suggests that the midlatitude ionosphere is more active even during geomagnetically quiet days than previously thought and that further studies are necessary. This is particularly relevant for the GNSS user community and related applications

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

pilot ionosonde network for identification of traveling ionospheric disturbances

Travelling Ionospheric Disturbances (TIDs) are the ionospheric signatures of atmospheric gravity waves (AGWs). Their identification and tracking is important because the TIDs affect all services that rely on predictable ionospheric radio wave propagation. Although various techniques have been proposed to measure TID characteristics, their real-time implementation still has several difficulties. In this contribution, we present a new technique, based on the analysis of oblique Digisonde-to-Digisonde (D2D) "skymap" observations, to directly identify TIDs and specify the TID wave parameters based on the measurement of angle-of-arrival, Doppler frequency, and time-of-flight of ionospherically reflected high-frequency (HF) radio pulses. The technique has been implemented for the first time for the Net-TIDE project with data streaming from the network of European Digisonde DPS4D observatories. The performance is demonstrated during a period of moderate auroral activity, assessing its consistency with independent measurements such as data from auroral magnetometers and electron density perturbations from Digisondes and GNSS stations. Given that the different types of measurements used for this assessment were not made at exactly the same time and location, and that there was insufficient coverage in the area between the AGW sources and the measurement lo cations, we can only consider our interpretation as plausible and indicative for the reliability of the extracted TID characteristics. In the framework of the new TechTIDE project (European Commission H2020), a retrospective analysis of the Net-TIDE results in comparison with those extracted from GNSS TEC-based methodologies is currently being attempted, and the results will be the objective of a follow up paper

Study of the F3 and StF4 Layers at Tucumán Near the Southern Crest of the Equatorial Ionization Anomaly in Western South America

The present investigation reports for the first time seasonal and solar activity variations of F3 and StF4 layers at the low-latitude station of Tucumán (26.9°S, 65.4°W; dip latitude 13.9°S), Argentina, by considering ionograms recorded from 2007 to 2015 by an Advanced Ionospheric Sounder-Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) digital ionosonde. Occurrences of F3 and StF4 layers are found to be higher during summer months, while they are almost nil in winter. Moreover, occurrences of F3 and StF4 layers show a solar activity dependence with higher values during high solar activity. The solar activity dependence of F3 over Tucumán is similar to that reported earlier for the low-latitude station of São José dos Campos, Brazil (dip latitude 14.1°S), but different than that reported for the near-equatorial station of Palmas (dip latitude 6.6°S), Brazil. On the other hand, the solar cycle dependence of StF4 layer is consistent with the one obtained at Palmas. This highlights the complex nature of electrodynamics characterizing the ionosphere from the magnetic equatorial to low latitudes. Moreover, as shown in previous studies, the StF4 layer is always preceded and followed by the F3 layer, and it shows a shorter lifetime than that of the F3 layer. During the considered period, 1812 days were analyzed and the F3 layer was found in 370 days (20.4%), while the StF4 layer was found in 41 days (2.3%). This means that the StF4 stratification is seen during 11% of F3 layer days.Fil: Tardelli, A.. Universidade do Vale do Paraiba; BrasilFil: Pezzopane, M.. Istituto Nazionale di Geofisica e Vulcanologia; ItaliaFil: Fagundes, P. R.. Universidade do Vale do Paraiba; BrasilFil: Venkatesh, K.. Universidade do Vale do Paraiba; BrasilFil: Pillat, V. G.. Universidade do Vale do Paraiba; BrasilFil: Cabrera, Miguel Angel. Universidad Tecnológica Nacional; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Electricidad, Electrónica y Computación. Laboratorio de Telecomunicaciones; ArgentinaFil: Ezquer, Rodolfo Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionósfera; Argentin

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