Performance evaluation of IRI-Plas 2017 model with ionosonde data measurements of ionospheric parameters.

This study presents an evaluation of the performance of the International Reference Ionosphere Model augmented with the Plasmasphere (IRI Plas 2017) from the Addis Ababa Ionosonde Station, Ethiopia, for measuring ionospheric parameters at geographic (9.00o N, 38.70o E) and geomagnetic (0.16o N, 110.44o E) location on selected days of 2014. During comparison hourly and daily variability of the ionospheric parameters of the electron density profile (Neh), maximum electron density (NmF2) and maximum height (hmF2) measurements are considered. When evaluating the IRI Plas model using ionosonde data, the percentage deviation and correlation coefficient (R) were used as measures of IRI Plas model performance. In general, the overall results of the study show that the IRI Plas 2017 model mostly overestimates at most altitudes and hours of electron density measurements. The IRI Plas model has an acceptable fit with the ionosonde electron density measurements at altitudes of 100 km-200 km, mostly during the hours between 03LT and 09 LT and 15 LT-21 LT, while the model biases in other altitudes and hours with overestimates or underestimates in the ionosonde electron density measurements. The IRI-Plas 2017 model has a good correlation after midnight and around midday hours, with about ±2% point deviation from the ionosonde electron density measurement. The model has a high percentage deviation value for electron density measurements, mostly between altitudes of 200 km and 450 km and during early nighttime and before midnight hours. IRI-Plas model measurements of NmF2 and hmF2 are mostly underestimated from the ionosonde data during the nighttime (21 LT-09 LT) and overestimated during the daytime (09 LT-21 LT). The NmF2 values measured with the model are more consistent with ionosonde values than hmF2 values.

Middle-Scale Ionospheric Disturbances Observed by the Oblique-Incidence Ionosonde Detection Network in North China after the 2011 Tohoku Tsunamigenic Earthquake.

The 2011 Tohoku earthquake and the following enormous tsunami caused great disturbances in the ionosphere that were observed in various regions along the Pacific Ocean. In this study, the oblique-incidence ionosonde detection network located in North China was applied to investigate the inland ionospheric disturbances related to the 2011 tsunamigenic earthquake. The ionosonde network consists of five transmitters and 20 receivers and can monitor regional ionosphere disturbances continuously and effectively. Based on the recorded electron density variations along the horizontal plane, the planar middle-scale ionospheric disturbances (MSTIDs) associated with the 2011 Tohoku tsunamigenic earthquake were detected more than 2000 km west of the epicenter about six hours later. The MSTIDs captured by the Digisonde, high-frequency (HF) Doppler measurement, and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellite provided more information about the far-field inland propagation characteristics of the westward propagating gravity waves. The results imply that the ionosonde network has the potential for remote sensing of ionospheric disturbances induced by tsunamigenic earthquakes and provide a perspective for investigating the propagation process of associated gravity waves.

Long-Term Observation of the Quasi-3-Hour Large-Scale Traveling Ionospheric Disturbances by the Oblique-Incidence Ionosonde Network in North China.

The oblique-incidence ionosonde network in North China is a very unique system for regional ionospheric observation. It contains 5 transmitters and 20 receivers, and it has 99 ionospheric observation points between 22.40° N and 33.19° N geomagnetic latitudes. The data of the ionosonde network were used to investigate the statistical characteristics of the quasi-3-h large-scale traveling ionospheric disturbances (LSTIDs). From September 2009 to August 2011, 157 cases of the quiet-time LSTIDs were recorded; 110 cases traveled southward, 46 cases traveled southwestward and only 1 case traveled southeastward. The LSTIDs mainly appeared between 10:00 and 19:00 LT in the months from September to the following May. We compared the data of the Beijing, Mohe and Yakutsk digisondes and found that the LSTIDs are most likely to come from the northern auroral region. These LSTIDs may be induced by the atmospheric gravity waves (AGWs) and presented obvious seasonal and diurnal varying features, indicating that the thermospheric wind field has played an important role.

Comparison of SuperDARN peak electron density estimates based on elevation angle measurements to ionosonde and incoherent scatter radar measurements.

Measurements of the electron density at the F region peak by the Canadian Advanced Digital Ionosonde (CADI) and the Resolute Incoherent Scatter Radar (RISR) are used to assess the quality of peak electron density estimates made from elevation angle measurements by the Super Dual Auroral Radar Network (SuperDARN) high-frequency radar at Rankin Inlet (RKN). All three instruments monitor the ionosphere near Resolute Bay. The CADI-RKN joint dataset comprises measurements between 2008 and 2017 while RISR-RKN dataset covers about 60 daylong events in 2016. Reasonable agreement between the RKN estimates and measurements by CADI and RISR is shown. Two minor discrepancies are discussed: RKN radar daytime peak electron density overestimation by ~ 10% and underestimation by up to 30% in other time sectors. In winter nighttime and dawn, cases were identified in which the RKN radar significantly overestimates the peak electron density. This occurs when the phase in the RKN interferometer measurements is incorrectly shifted by 2 π , and this is most significant when electron densities are low. Statistical fitting to the joint data sets, split into four time sectors of a day, has been done and parameters of the fit have been determined. These allow slight adjustment of measured real-time RKN values to better reflect real peak electron densities in the ionosphere within its field of view.

Calibrating an Ionosonde for Ionospheric Attenuation Measurements.

Vertical ionospheric soundings have been performed at almost all ionospheric observatories with little attention to measuring the attenuation of the signal between transmission and reception. When the absorption has been determined, this has been achieved by comparing the received power after the first and second reflections, but this method has some limitations due to the unknown reflection coefficient of the ground and the non-continuous presence of the second reflection. This paper deals with a different method based on precise calibration of the sounding system, allowing determination of absolute signal attenuation after a single reflection. This approach is affected by a systematic error due to imperfect calibration of the antennas, but when the focus of interest is to measure a trend over a specified period, it is very accurate. The article describes how calibration was implemented, the measurement output formats, and finally it presents some results from a meaningful set of measurements in order to demonstrate what this method can accomplish.

Implementation of an Electronic Ionosonde to Monitor the Earth's Ionosphere via a Projected Column through USRP.

This document illustrates the processes carried out for the construction of an ionospheric sensor or ionosonde, from a universal software radio peripheral (USRP), and its programming using GNU-Radio and MATLAB. The development involved the in-depth study of the characteristics of the ionosphere, to apply the corresponding mathematical models used in the radar-like pulse compression technique and matched filters, among others. The sensor operates by firing electromagnetic waves in a frequency sweep, which are reflected against the ionosphere and are received on its return by the receiver of the instrument, which calculates the reflection height through the signal offset. From this information and a series of calculations, the electron density of the terrestrial ionosphere could be obtained. Improving the SNR of received echoes reduces the transmission power to a maximum of 400 W. The resolution associated with the bandwidth of the signal used is approximately 5 km, but this can be improved, taking advantage of the fact that the daughterboards used in the USRP allow a higher sampling frequency than the one used in the design of this experiment.