Electron Density Disturbances Research Articles

Observations and simulations of large-scale traveling ionospheric disturbances during the January 14-15, 2022 geomagnetic storm

Using the total electron content (TEC) observations from GPS, and simulations from the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM), this work investigates the large-scale traveling ionospheric disturbances (LSTIDs) and the possible involved drivers during the geomagnetic storm on January 14-15, 2022. Based on the term analysis of O+ continuity equation in TIEGCM, it is found that the traveling atmospheric disturbances in equatorward winds are responsible for the LSTIDs, with minor contributions from plasma drifts owing to the prompt penetration electric field. A strong interhemispheric asymmetry of the LSTIDs is observed, which might be attributed to both the equatorward wind disturbances and background plasma. The stronger wind (plasma) disturbances occurs in the winter hemisphere than that in the summer hemisphere. The maximum magnitude of LSTIDs in electron density disturbances occurs at ∼250 and ∼270 km in the northern and southern hemispheres, respectively, owing to both the thermospheric equatorward winds and background plasma. An interesting phenomenon that tail-like LSTIDs occur at the dip equator and low latitudes might be related to the eruption of the Tonga volcano, but it is not well reproduced in TIEGCM that deserves further exploration in a future study.

Statistical Relationship of Ionospheric Disturbances Caused by Typhoon Extinction on the Sea

AbstractBased on the data of magnetic field and electronic density of SWARM, and Total Electron Content, this paper screened six typhoons that died out on the sea. We studied how typhoons affected the ionosphere when they died out without the influence of topography and other factors. The statistical results show that during the extinction of typhoons, the magnetic disturbances all appeared, and the electron density disturbances were observed in five typhoons. The frequency of the electronic density disturbance is slightly higher than the magnetic disturbance. The range of the electronic density disturbance is mostly five or six hundred kilometers and relatively concentrated. The range of the magnetic disturbance can reach about two thousand kilometers and is relatively scattered. Our results indicate that the extinction of typhoon may affect the ionosphere through acoustic gravity waves (AGWs). The AGWs is not generated by friction, but may be from the typhoon itself or a new phenomenon when the typhoon dies out.

Simulation of Electron Density Disturbance in the Lower Ionosphere Caused by Thundercloud Electrostatic Fields

In this study, we simulated the electron density disturbance at night in the bottom of the ionosphere caused by the electrostatic field in a thundercloud. The simulation was conducted using the charge of the thundercloud as the source, by incorporating a more up-to-date conductivity profile, and using the ion chemistry model for the lower ionosphere. The results revealed that a thundercloud charge of 30–100 C can cause a disturbance in the electron density in the lower ionosphere, decreasing to 40% of the original value or increasing to 160% of the original value. The electron density disturbance occurs mainly below an altitude of 80 km, and its peak is located at an altitude of 70 km, with a regional horizontal radius of about 50–75 km. The simulation results of this study improve the theory of Salem et al and extend the original one-dimensional model to three-dimensional space.

Detection and Three‐Dimensional Reconstruction of Concentric Traveling Ionosphere Disturbances Induced by Hurricane Matthew on 7 October 2016

AbstractThis paper reports the first high‐resolution 4‐dimensional ionospheric disturbance caused by hurricane Matthew on 7 October 2016. The temporal as well as vertical and horizontal variations of the concentric traveling ionospheric disturbances (CTIDs) were reconstructed using 3‐dimensional computerized ionospheric tomography (3DCIT) technology, based upon the Global Navigation Satellite System data from the dense receiver network over North America. The frequency range of disturbances was determined by spectrum analysis, and a Butterworth band‐pass filter was used to de‐trend the total electron content (TEC) sequences to determine TIDs. A remarkable CTID segment was detected at a distance of 1,000–1,500 km from the hurricane eye at ∼5:40–6:10 UT on 7 October 2016, moving westward with the horizontal phase velocity of ∼153.4 m/s, the period of ∼30 min and the horizontal wavelength of ∼276.1 km. The positive and negative wavefronts dominated the CITD at different times during the event. From 4:00 to 8:00 UT, the altitudinal variation of the CTIDs in electron density exhibited clear downward phase progression predominately in the range of 150–400 km altitudes; however, the percentage of electron density disturbances was larger below 250 km. The inverted cone‐like geometry of CTID wavefronts was presented. The vertical phase velocities of the CTIDs ∼1,100 km away from the hurricane eye in the northwest direction near 88°W, 34°N were ∼203.7–277.8 m/s, and at the same location, the horizontal phase velocities at 300 km altitude were ∼149.1–181.5 m/s, slightly larger than those at 200 km altitude (∼145.1–178.5 m/s).

Ionospheric effects of the 5–6 January 2019 eclipse over the People's Republic of China: results from oblique sounding

Abstract. This paper deals with the variations in the Doppler spectra and in the relative amplitudes of the signals observed at oblique incidence over the People's Republic of China (PRC) during the partial solar eclipse of 5–6 January 2019 and on reference days. The observations were made using the multifrequency multipath radio system for sounding the ionosphere at oblique incidence. The receiver system is located at the Harbin Engineering University, PRC, and 14 HF broadcasting station transmitters are used for taking measurements along the following radio-wave propagation paths: Lintong/Pucheng to Harbin, Hwaseong to Harbin, Chiba/Nagara to Harbin, Hailar/Nanmen to Harbin, Beijing to Harbin (three paths), Goyang to Harbin, Ulaanbaatar/Khonkhor to Harbin, Yakutsk to Harbin (two paths), Shijiazhuang to Harbin, Hohhot to Harbin, and Yamata to Harbin. The specific feature of this partial solar eclipse was that it occurred during the local morning with a geomagnetic disturbance (Kp ≈ 3−) in the background. The response of the ionosphere to the solar eclipse has been inferred from temporal variations in the Doppler spectra, the Doppler shift, and the signal relative amplitude. The partial solar eclipse was found to be associated with broadening of the Doppler spectrum, up to ± 1.5 Hz, alternating sign Doppler-shift variations, up to ± 0.5 Hz, in the main ray, and quasi-periodic Doppler-shift changes. The relative amplitude of electron density disturbances in the 15 min period of atmospheric gravity wave field and in the 4–5 min period of infrasound wave field is estimated to be 1.6 %–2.4 % and 0.2 %–0.3 %, respectively. The estimates of a maximum decrease in the electron density are in agreement with the observations.

Dynamic processes in the magnetic field and in the ionosphere during the 30 August–2 September 2019 geospace storm: influence on high frequency radio wave characteristics

Abstract. The concept that geospace storms are comprised of synergistically coupled magnetic storms, ionospheric storms, atmospheric storms, and storms in the electric field originating in the magnetosphere, the ionosphere, and the atmosphere (i.e., electrical storms) was validated a few decades ago. Geospace storm studies require the employment of multiple-method approaches to the Sun–interplanetary medium–magnetosphere–ionosphere–atmosphere–Earth system. This study provides general analysis of the 30 August–2 September 2019 geospace storm, the analysis of disturbances in the geomagnetic field and in the ionosphere, as well as the influence of the ionospheric storm on the characteristics of high frequency (HF) radio waves over the People's Republic of China. The main results of the study are as follows. The energy and power of the geospace storm have been estimated to be 1.5×1015 J and 1.5×1010 W, and thus, this storm is weak. The energy and power of the magnetic storm have been estimated to be 1.5×1015 J and 9×109 W, i.e., this storm is moderate, and a characteristic feature of this storm is the duration of the main phase of up to 2 d. The recovery phase also was lengthy and was no less than 2 d. On 31 August and 1 September 2019, the variations in the H and D components attained 60–70 nT, while the Z-component variations did not exceed 20 nT. On 31 August and 1 September 2019, the level of fluctuations in the geomagnetic field in the 100–1000 s period range increased from 0.2–0.3 to 2–4 nT, while the energy of the oscillations showed a maximum in the 300–400 to 700–900 s period range. During the geospace storm, a moderately to strongly negative ionospheric storm manifested itself by the reduction in the ionospheric F-region electron density by a factor of 1.4 to 2.4 times on 31 August and 1 September 2019, compared to the its values on the reference day. Appreciable disturbances were also observed to occur in the ionospheric E region and possibly in the Es layer. In the course of the ionospheric storm, the altitude of reflection of radio waves could sharply increase from ∼150 to ∼300–310 km. The atmospheric gravity waves generated within the geospace storm modulated the ionospheric electron density; for the ∼30 min period oscillation, the amplitude of the electron density disturbances could attain ∼40 %, while it did not exceed 6 % for the ∼15 min period. At the same time, the height of reflection of the radio waves varied quasi-periodically with a 20–30 km amplitude. The results obtained have made a contribution to the understanding of the geospace storm physics, to developing theoretical and empirical models of geospace storms, to the acquisition of detailed understanding of the adverse effects that geospace storms have on radio wave propagation, and to applying that knowledge to effective forecasting of these adverse influences.

Visualizing sporadic E using aeronautical navigation signals at VHF frequencies

To understand the dynamical properties of sporadic E layer (Es), we have developed a method to visualize the two-dimensional spatial structure of Es by monitoring the occurrence of anomalous propagation of VHF waves used for aeronautical navigation systems in combination with the electron density disturbance index ROTI, that is the Rate of total electron content (TEC) Index obtained from ground-based GPS receivers. We introduce a case of strong Es layer which occurred for ~4 h during daytime of July 4, 2019. In this interval, we succeeded in imaging the structure of Es elongating more in the east–west direction and moving northward gradually. This result indicates that the combination of network observations of aeronautical navigation signals and ROTI is capable of imaging the 2D structure of Es in a wide area including the sea surface, which enables us to discuss the dynamical characteristics and generation mechanism of Es.

The influence of the ionospheric disturbance on the ground based VLF transmitter signal recorded by LEO satellite – Insight from full wave simulation

The earthquakes could induce ionospheric electron density disturbance at D/E, F layer and even topside of ionosphere. Subsequently the ionospheric disturbance would change the electromagnetic field from the ground based VLF transmitter. Nowadays, the electromagnetic field recorded by Low earth orbit (LEO) satellite have been used to study the possible seismic anomalies frequently. It is essential to study systematically how the ionospheric disturbance influences the electromagnetic field at the altitude of LEO satellite theoretically. In this paper, we construct a full wave model to simulate the influence of the amplitude, altitude, and scale of the ionospheric disturbance on the electromagnetic field in the ionosphere from the ground based VLF transmitter. The result shows the electromagnetic field at the altitude of satellite changes obviously when the wave encounters an ionospheric disturbance in the D/E layer. The variation of the electromagnetic field increases with the amplitude and scale of the ionospheric disturbance. However, the influence of the ionospheric disturbance in the F layer just has a local effect on the electromagnetic field. The influence of ionospheric disturbance in the nighttime on the variation of electromagnetic field is smaller compared with it in the daytime. These conclusions can improve our understanding of using electromagnetic field observed by satellite to study seismic anomalies.

Tsunami-Launched Acoustic Wave in the Layered Atmosphere: Explicit Formulas Including Electron Density Disturbances

The problem of the propagation of acoustic wave disturbance initiated by a boundary condition is used to simulate a disturbance of atmospheric gas caused by a rise of water masses. The boundary condition is a function of a dynamic variable that is defined on the border of the problem domain. In this work, it is chosen in such a way that its parameters and form correspond to disturbances in the gas layer produced by a tsunami wave at the air–water interface. The atmosphere is approximately described as a 1D multilayer gas media with an exponential structure of density in each layer. The boundary conditions are set at the interface between water–air and gas layers. These determine the direction of propagation and the ratio of dynamic variables characterizing an acoustic wave. The relationship between such variables (pressure, density, and velocity) is derived by means of projection operators on the subspaces of the z-evolution operator for each layer. The universal formulas for the perturbation of atmospheric variables in an arbitrary layer are obtained in frequency and time domains. As a result, explicit expressions are derived that determine the spectral composition and vertical velocity, by the stationary phase method, of the acoustic disturbance of the atmosphere at an arbitrary height, including the heights of the ionosphere. In return, this can be used to calculate the ionospheric effect. The effect is described by the explicit formula for electron density evolution, which is the solution of the diffusion equation. This forms a quick algorithm for early diagnostics of tsunami waves.

Study of ULF-VLF wave propagation in the near-Earth environment for earthquake prediction

This work presents the study on the electromagnetic wave penetration and propagation into the ionosphere in the frequency range of 100 Hz to 3 kHz and 3 kHz to 10 kHz, corresponding to the Ultra Low Frequency (ULF) and Very Low Frequency (VLF), respectively, for various types of applications including earthquake prediction. The main idea here is to investigate the efficiency of whistler/helicon wave generation in the E-region under different ionospheric conditions by solving Maxwell’s equations and incorporating ionospheric conditions through the Hall, Pedersen, and parallel conductivities. Specifically, the effect of pulse and continuous probing of the lower ionosphere with ULF-VLF signals and the generation of secondary waves and currents due to high conductivities in the E-region is studied. The characteristics and applications of the excited Helicon ULF-VLF waves are discussed. The effect of background ionospheric parameters such as the electron density and ionospheric disturbances due to pre-earthquake conditions and other natural sources including lightning discharges on the excitation and penetration of ULF-VLF waves into the E-region is investigated. The efficiency of this technique in developing a monitoring system to detect and locate seismic activities is discussed.

Ionospheric processes observed with the passive oblique-incidence HF Doppler radar

Urgency. The urgency is caused by the need to continuously monitor with radio instrumentation dynamic processes acting in the ionosphere, which arise due to variations in space weather, the impact of high-energy sources of natural and anthropogenic origin. To meet this challenge, V. N. Karazin National University and Harbin Engineering University specialists has developed a coherent multi-frequency multi-path radio system for obliquely probing the ionosphere. Purpose of Work. The paper illustrates the instrument capability for the study of dynamic processes arising in the ionosphere during a solar terminator, a moderate earthquake, a strong ionospheric storm, and in the cource of a partial solar eclipse. Techniques and Methodology. The system design is base on the software-defined radio (SDR) technology. The system is capable of receiving radio waves in the 10 kHz – 30 MHz band. The versatile computer software permits us to adjust the system for solving various problems. The number of the radio propagation paths and their orientation depends on the problem being solved. The premise upon which this radio system operation is based is measurements of the Doppler shift of the frequency. The autoregressive algorithm provides a 0.02 Hz root-mean-square Doppler line error and 7.5-s time resolution. Having the Doppler spectrum time dependencies for various radio paths archived, time series corresponding to various radio-wave modes undergo further processing. Results. As an example of successful instrument performance, dynamic processes operating in the course of a dusk terminator, the moderate (magnitude 5.9) earthquake on July 7, 2018, the strong ionospheric storm on August 26, 2018, and the partial (0.74 magnitude) solar eclipse over China on August 11, 2018 have been investigated. The ionospheric response to the impact of energy sources of various nature has been detected and investigated; it was accompanied by an increase in the number of rays, Doppler spectrum broadening, aperiodic and quasi-periodic variations in the Doppler shift of the frequency, generation of alternating sign variations in the electron density and wave disturbances having atmospheric gravity wave and infrasound parameters. Conclusions. The radio system located at the Harbin Engineering University campus successfully performs continuous radio monitoring of dynamic processes caused by various energy source in the ionosphere.

After-effects of geomagnetic storms: statistical analysis and theoretical explanation

Our previous studies have shown the presence of daytime positive electron density disturb-ances during several days after the start of the recovery phase. The aim of this paper is to study after-effects of geomagnetic storms (after-storm effects), i.e. ionospher-ic effects observed on the 3–5th day after the beginning of the storm recovery phase. From numerical calcula-tions with the GSM TIP model, we have found the main mechanisms for the formation of the after-storm effects. Using Irkutsk (52° N, 104° E) and Kaliningrad (54° N, 20° E) ionosonde data, we have carried out a statistical analysis of daytime ionospheric responses to geomagnetic storms. As a result of the analysis, we obtained averaged ionospheric responses at the beginning of the storm recovery phase and for five consecutive days. The statistical analysis results received near the beginning of the recovery phase are in good agreement with the well-known ionospheric effects of geomagnetic storms obtained in previous studies. For the first time, the obtained statistics of iono-spheric responses observed on the 3–5th day after the beginning of the recovery phase allowed us to reveal the dependence of after-storm ionospheric effects on season, storm intensity, and ionosonde geomagnetic latitude. In addition, we for the first time present the interpretation of after-storm ionospheric effects from numerical simulation results.

Эффекты последействий геомагнитных бурь: статистический анализ и теоретическое объяснение

Our previous studies have shown the presence of daytime positive electron density disturb-ances during several days after the start of the recovery phase. The aim of this paper is to study after-effects of geomagnetic storms (after-storm effects), i.e. ionospher-ic effects observed on the 3–5th day after the beginning of the storm recovery phase. From numerical calcula-tions with the GSM TIP model, we have found the main mechanisms for the formation of the after-storm effects. Using Irkutsk (52° N, 104° E) and Kaliningrad (54° N, 20° E) ionosonde data, we have carried out a statistical analysis of daytime ionospheric responses to geomagnetic storms. As a result of the analysis, we obtained averaged ionospheric responses at the beginning of the storm recovery phase and for five consecutive days. The statistical analysis results received near the beginning of the recovery phase are in good agreement with the well-known ionospheric effects of geomagnetic storms obtained in previous studies. For the first time, the obtained statistics of iono-spheric responses observed on the 3–5th day after the beginning of the recovery phase allowed us to reveal the dependence of after-storm ionospheric effects on season, storm intensity, and ionosonde geomagnetic latitude. In addition, we for the first time present the interpretation of after-storm ionospheric effects from numerical simulation results.

Modeling of Decameter Radio-Wave Propagation Under Conditions of a Wave-Like Electron-Density Disturbance

We present the results of numerical modeling of decameter radio-wave propagation on a weakly oblique Vasilsursk—Nizhny Novgorod path under conditions of traveling ionospheric disturbances. A comparison is made with the chirp sounding data obtained in winter with an average solar activity. The direction–velocity characteristics of the wave-like disturbances are determined. It is shown that in the daytime, in a quiet magnetic environment, medium-scale wave-like disturbances of the electron density with sizes about 100 km, a period of 15 min, and relative amplitude δ ≈ 0.1 can be responsible for the crescent traces on the ionograms. The wave-like disturbances propagate at a velocity of 110 m/s at the angle β ≈ −45° to the horizon with the wave vector oriented predominantly in the east–west direction.

Multi-scale ionospheric irregularities occurrence over South America during the St. Patrick's day storm on March 17, 2015

During the solar cycle 24 there was a very intense geomagnetic storm due to the St. Patrick's day storm and the effects of this storm on ionosphere has become a topic of extensive space weather investigation. Up to now several aspects of the St. Patrick's ionospheric storm have been study such as the prompt penetration electric fields (PPEFs), TEC changes, electron density disturbances, plasma drift, O+ concentration modification, hemispherical asymmetry developments, equatorial ionization anomaly (EIA) modification, and ionospheric irregularities. Besides all these important studies, there are some essential aspects, which have not been addressed yet, related to the occurrence of multi-scale ionospheric irregularities. In this paper, we present and discuss the generation and suppression of multi-scale ionospheric irregularities, using the observations conducted in the Latin American Sector from 4 ionosondes, 20 dual frequency GPS stations, and JULIA radar observations during the month of March 2015, which includes the St. Patrick's day geomagnetic storm period. Suppression of large-small scales ionospheric irregularities has occurred during the main and second night of the recovery phases. However, during the first night of recovery phase there was post-midnight ionospheric irregularities.

Similarity and differences in morphology and mechanisms of the <i>fo</i>F2 and TEC disturbances during the geomagnetic storms on 26–30 September 2011

Abstract. This study presents an analysis of the ground-based observations and model simulations of ionospheric electron density disturbances at three longitudinal sectors (eastern European, Siberian and American) during geomagnetic storms that occurred on 26–30 September 2011. We use the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) to reveal the main mechanisms influencing the storm-time behavior of the total electron content (TEC) and the ionospheric F2 peak critical frequency (foF2) during different phases of geomagnetic storms. During the storm's main phase the long-lasting positive disturbances in TEC and foF2 at sunlit mid-latitudes are mainly explained by the storm-time equatorward neutral wind. The effects of eastward electric field can only explain the positive ionospheric storm in the first few hours of the initial storm phase. During the main phase the ionosphere was more changeable than the plasmasphere. The positive disturbances in the electron content at the plasmaspheric heights (800–20 000 km) at high latitudes can appear simultaneously with the negative disturbances in TEC and foF2. The daytime positive disturbances in foF2 and TEC occurred at middle and low latitudes and at the Equator due to n(O) ∕ n(N2) enhancement during later stage of the main phase and during the recovery phase of the geomagnetic storm. The plasma tube diffusional depletion and negative disturbances in electron and neutral temperature were the main formation mechanisms of the simultaneous formation of the positive disturbances in foF2 and negative disturbances in TEC at low latitudes during the storm's recovery phase.

Spatiotemporal distributions of the electron density in the ionosphere by records of the total electron content and phase of VLF radio signals

Features of the structure and dynamics of the ionospheric plasma are studied in a comparison the ionospheric total electron content measurements with the phase and amplitude measurements of VLF–LF radio signals on global and regional paths. The ionospheric structure over Europe is reconstructed. The spatiotemporal dynamics of moving ionospheric disturbances under conditions of a powerful geomagnetic storm of March 17, 2015, is examined based on the reconstruction results. Analysis of the phase variation of VLF radio signals, together with the TEC measurement data, is not only an additional tool in the study of the dynamics of ionospheric disturbances; it also makes it possible to estimate electron density disturbances in different ionospheric layers.

Ionospheric electron density perturbations during the 7–10 March 2012 geomagnetic storm period

From 7 to 10 March 2012 a series of magnetospheric disturbances caused perturbations in the ionospheric electron density. Analyzing the interplanetary causes in each phase of this disturbed period, in comparison with the total electron content (TEC) disturbances, we have concluded that the interplanetary solar wind controls largely the ionospheric response. An interplanetary shock detected at 0328UT on 7 March caused the formation of prompt penetrating electric fields in the dayside that transported plasma from the near-equatorial region to higher in attitudes and latitudes forming a giant plasma fountain which is part of the so-called dayside ionospheric super-fountain. The super-fountain produces an increase in TEC which is the dominant effect at middle latitude, masking the effect of the negative storm. Simultaneously, inspecting the TEC maps, we found evidence for a turbulence in TEC propagating southward probably caused by large scale travelling ionospheric disturbances (LSTIDs) linked to auroral electrojet intensification. On 8 March, a magnetospheric sudden impulse at 1130UT accompanied with strong pulsations in all interplanetary magnetic field (IMF) components and with northward Bz component during the growth phase of the storm. These conditions triggered a pronounced directly driven substorm phase during which we observe LSTID. However, the analysis of DMSP satellite observations, provided with strong evidence for Sub-Auroral Polarization Streams (SAPS) formation that erode travelling ionospheric disturbances (TID) signatures. The overall result of these mechanisms can be detected in maps of de-trended TEC, but it is difficult to identify separately each of the sources of the observed perturbations, i.e. auroral electrojet activity and LSTIDs, super-fountain and SAPS.In order to assess the capability of the ionospheric profiler called Topside Sounder Model - assisted Digisonde (TaD model) to detect such perturbations in the electron density, electron density disturbances at heights from 200 to 1000km have been calculated with the TaD model and compared with slant TEC parameters obtained from GPS receivers co-located with the Digisondes whose data were used to generate the TaD model predictions. The model matches in qualitative terms the GPS TEC observed perturbations independently from the source. The physical mechanisms that govern the ionosphere, such as ion drag by neutral winds along magnetic field lines, E×B drifts, and increased recombination due to the neutral composition changes, offer various combinations of foF2, hmF2 and TEC variations, which TaD resolves. Counterwise, TaD can help the interpretation of various physical scenarios which cannot be achieved if solely TEC or F layer variations are considered.

Long-term changes in space weather effects on the Earth’s ionosphere

Certain limitations that have been identified in existing ionospheric prediction capabilities indicate that the deeper understanding and the accurate formulation of the ionospheric response to external forcing remain always high priority tasks for the research community. In this respect, this paper attempts an investigation of the long-term behavior of the ionospheric disturbances from the solar minimum between the solar cycles 23 and 24 up to the solar maximum of solar cycle 24. The analysis is based on observations of the foF2 critical frequency and the hmF2 peak electron density height obtained in the European region, records of the Dst and AE indices, as well as measurements of energetic particle fluxes from NOAA/POES satellites fleet. The discussion of the ionospheric behavior in a wide range of geophysical conditions within the same solar cycle facilitates the determination of general trends in the ionospheric response to different faces of space weather driving. According to the evidence, the disturbances in the peak electron density reflect mainly the impact of geoeffective solar wind structures on the Earth’s ionosphere. The intensity of the disturbances may be significant (greater than 20% with respect to normal conditions) in all cases, but the ionospheric response tends to have different characteristics between solar minimum and solar maximum conditions. In particular, in contrast to the situation in solar maximum, in solar minimum years the solar wind impact on the Earth’s ionosphere is mainly built on the occurrence of ionization increases, which appear more frequent and intense than ionization depletions. The ionization enhancements are apparent in all local time sectors, but they peak in the afternoon hours, while a significant part of them seems not related with an F2 layer uplifting. Taking into account the main interplanetary drivers of the disturbances in each case, i.e. high speed streams (HSSs) and corotating interaction regions (CIRs) in solar minimum and coronal mass ejections (CME) in solar maximum, we argue that the identified tendency may be considered as evidence of the ionospheric response to different solar wind drivers.

Wave processes in the ionosphere over Europe that accompanied the solar eclipse of March 20, 2015

Ionospheric disturbances at an altitude of 300 km that accompanied the solar eclipse of March 20, 2015, have been analyzed based on the ionosondes located in Europe. It has been confirmed that the eclipse was accompanied by the generation of gravity waves in the neutral atmosphere and traveling ionospheric disturbances. The period of the latter was 30–100 min, and the amplitude of relative electron density disturbances was 4–19%. The disturbances continued for not less than 2 h. During the eclipse, the disturbance amplitude more frequently increased. It decreased in one case, since the wave process observed previously was suppressed by the process generated by the eclipse.