Sporadic Es Layer Research Articles

Influence of geomagnetic disturbances on scintillations of GLONASS and GPS signals as observed on the Kola Peninsula

We have compared effects of geomagnetic disturbances during magnetic storms of various types (CME and CIR) and during an isolated substorm on scintillations of GLONASS and GPS signals, using a Septentrio PolaRx5 receiver installed in Apatity (Murmansk Region, Russia). We analyze observational data for 2021. The magnetic storms of November 3–4, 2021 and October 11–12, 2021 are examined in detail. The November 3–4, 2021 magnetic storm was one of the most powerful in recent years. The analysis shows that the scintillation phase index reaches its highest values during nighttime and evening substorms (σϕ≈1.5–1.8), accompanied by a negative bay in the magnetic field. During magnetic storms, positive bays in the magnetic field, associated with an increase in the eastward electrojet, lead, however, to quite comparable values of the phase scintillation index.
 An increase in phase scintillations during nighttime and evening disturbances correlates with an increase in the intensity of ULF waves (Pi3/Pc5 pulsations) and with the appearance of aurora arcs. This confirms the important role of ULF waves in forming the auroral arc and in developing ionospheric irregularities. The predominance of the green line in the spectrum of auroras indicates the contribution of disturbances in the ionospheric E layer to the scintillation increase. Pulsating auroras, associated with ionospheric disturbances in the D layer, do not lead to a noticeable increase in phase scintillations. Analysis of ionospheric critical frequencies according to ionosonde data from the Lovozero Hydrometeorological Station indicates the contribution of the sporadic Es layer of the ionosphere to jumps in phase scintillations.
 The difference between phase scintillation values on GLONASS and GPS satellites during individual disturbances can be as great as 1.5 times, which may be due to different orbits of the satellites. At the same time, the level of GLONASS/GPS scintillations at the L2 frequency is higher than at the L1 frequency. We did not find an increase in the amplitude index of scintillations during the events considered.

Влияние геомагнитных возмущений на сцинтилляции сигналов ГЛОНАСС и GPS спутников по данным наблюдений на Кольском полуострове

We have compared effects of geomagnetic disturbances during magnetic storms of various types (CME and CIR) and during an isolated substorm on scintillations of GLONASS and GPS signals, using a Septentrio PolaRx5 receiver installed in Apatity (Murmansk Region, Russia). We analyze observational data for 2021. The magnetic storms of November 3–4, 2021 and October 11–12, 2021 are examined in detail. The November 3–4, 2021 magnetic storm was one of the most powerful in recent years. The analysis shows that the scintillation phase index reaches its highest values during nighttime and evening substorms (σϕ≈1.5–1.8), accompanied by a negative bay in the magnetic field. During magnetic storms, positive bays in the magnetic field, associated with an increase in the eastward electrojet, lead, however, to quite comparable values of the phase scintillation index.
 An increase in phase scintillations during nighttime and evening disturbances correlates with an increase in the intensity of ULF waves (Pi3/Pc5 pulsations) and with the appearance of aurora arcs. This confirms the important role of ULF waves in forming the auroral arc and in developing ionospheric irregularities. The predominance of the green line in the spectrum of auroras indicates the contribution of disturbances in the ionospheric E layer to the scintillation increase. Pulsating auroras, associated with ionospheric disturbances in the D layer, do not lead to a noticeable increase in phase scintillations. Analysis of ionospheric critical frequencies according to ionosonde data from the Lovozero Hydrometeorological Station indicates the contribution of the sporadic Es layer of the ionosphere to jumps in phase scintillations.
 The difference between phase scintillation values on GLONASS and GPS satellites during individual disturbances can be as great as 1.5 times, which may be due to different orbits of the satellites. At the same time, the level of GLONASS/GPS scintillations at the L2 frequency is higher than at the L1 frequency. We did not find an increase in the amplitude index of scintillations during the events considered.

Climatology of Nighttime Medium‐Scale Traveling Ionospheric Disturbances at Mid and Low Latitudes Observed by the DEMETER Satellite in the Topside Ionosphere During the Period 2005–2010

AbstractThermal ion measurements from the French Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions micro‐satellite have been used to study the climatology of nighttime Medium‐scale traveling ionospheric disturbances (MSTIDs) in the topside ionosphere at 650 km altitude during the 6 years of the satellite operation, from 2005 to 2010. This period encompasses the declining phase of solar cycle 23, the deep solar minimum of 2008–2009 and the early rise of solar cycle 24. MSTIDs were detected from the quasi‐periodic variations of the density of the dominant ionospheric O+ ions. Mostly present between ∼15° and ∼40° invariant latitudes with a small number of events in equatorial regions, the MSTIDs exhibit, on the average, larger occurrence rates in the Southern hemisphere with a peak in the Eastern Pacific‐South America longitude sector. The dependence of MSTID activity on solar activity appears more complex than the previously reported simple anti‐correlation. In addition to year‐to‐year variations, our study has, in particular, put in evidence a noticeable hemispheric asymmetry in the seasonal variations during the deep solar minimum of 2008–2009. These statistical observations provide a remarkable observational support to the key role of sporadic Es layers and the conjugate mapping of the associated electric fields. Yet, improved theoretical and numerical models, taking into account the actual inter‐hemispheric differences of the seasonal and solar activity variations of thermospheric and ionospheric processes, are needed for a better understanding of the highly complex MSTID phenomena.

Estimation earthquake occurrence probability in Kamchatka region based on seismological and complex of ionospheric precursors

In this paper the authors present the method of estimation of a region, waiting period and probability of strong earthquakes with KS ≥ 13.5 (M ≥ 6.0) in Kamchatka region based on the combination of mid-term and short-term predictive signs accompanying earthquake formation. The seismological predictive parameter ξP was taken as a mid-term precursor. It was calculated on the basis of the probabilistic model of seismic regime. A complex of ionospheric parameters was considered as short-term predictive signs with an earthquake waiting period of up to 5 days. It includes the K-layer, the sporadic Es layer of the r type, the critical frequency foF2, and the frequency stratification of the F2 layer. The probabilities of strong earthquakes with KS ≥ 13.5 (M ≥ 6.0) that occurred over the period 2019–2021 in an expected zone, determined by the parameter ξP, were estimated on the basis of Bayes method provided that a complex of anomalous parameters of the ionosphere was identified.

IMPACT OF METEOROLOGICAL STORMS ON THE E-REGION OF THE IONOSPHERE IN 2017–2018

The paper presents the results of observations of the sporadic Es layer during the period of meteorological disturbances in Kaliningrad in October 2017 and 2018 under quiet geomagnetic conditions. During the meteorological storms (October 29–30, 2017 and October 23–24, 2018), significant changes occurred in the dynamics of the Es-layer critical frequency. Observations of atmospheric and ionospheric disturbances in the Kaliningrad region show that the delay between the ionospheric response and the moment of maximum disturbances in atmospheric parameters is about 3 hours. These phenomena at the heights of the E-region might have been caused by propagation of acoustic-gravity waves generated by convective processes in the lower atmosphere during periods of a meteorological storm. Intensification of turbulent processes in the lower thermosphere leads to an increase in the atmospheric density and, accordingly, to higher recombination rates. This leads to a rapid decrease in the concentration of ions and, consequently, to a decrease in the critical frequency of the sporadic layer below the sensitivity threshold of ionosondes.

Влияние метеорологических штормов на область Е ионосферы в 2017–2018 гг

The paper presents the results of observations of the sporadic Es layer during the period of meteorological disturbances in Kaliningrad in October 2017 and 2018 under quiet geomagnetic conditions. During the meteorological storms (October 29–30, 2017 and October 23–24, 2018), significant changes occurred in the dynamics of the Es-layer critical frequency. Observations of atmospheric and ionospheric disturbances in the Kaliningrad region show that the delay between the ionospheric response and the moment of maximum disturbances in atmospheric parameters is about 3 hours. These phenomena at the heights of the E-region might have been caused by propagation of acoustic-gravity waves generated by convective processes in the lower atmosphere during periods of a meteorological storm. Intensification of turbulent processes in the lower thermosphere leads to an increase in the atmospheric density and, accordingly, to higher recombination rates. This leads to a rapid decrease in the concentration of ions and, consequently, to a decrease in the critical frequency of the sporadic layer below the sensitivity threshold of ionosondes.

Substorm Manifestations at Radio Paths of Oblique Ionospheric Sounding in the Arctic

The impact of geomagnetic substorms on radio propagation within the high-frequency (HF) range was analyzed using oblique ionospheric sounding data. These data were obtained from the unique system of radio paths that covers the whole region of the Russian Arctic. The study focused on the effects of two substorms with a twofold difference in intensity. Variations of four radio propagation parameters were studied: the maximum and lowest observed frequencies of the F2 ionospheric layer (F2MOF and F2LOF), and the same frequencies of the sporadic Es layer (EsMOF and EsLOF). Even the weak geomagnetic substorm (AEmax ~ 500 nT) significantly changed the ionosphere state and, consequently, the character of radio propagation at paths. The absorption of signals was more pronounced during a more intense substorm which resulted in loss of information during the transmissions through HF channels. The variations of propagation parameters (ΔMOF and ΔLOF) depend more on the path reflection point location and on the intensity of a substorm. Two substorms with a twofold difference in intensity had similar effects on ΔMOF, except for (a) the more pronounced smoothing of the Main Effect and (b) the higher ΔEsMOF amplitude during the intense substorm. Both issues are explained by more intense particle precipitations during the more intense disturbance.

Effects of Geomagnetic Storms in the Low-Latitude Ionosphere

A wide range of changes in parameters of the low-latitude ionosphere has been revealed during the periods of three intense geomagnetic storms that occurred in different seasons of 2015. Ionospheric parameters, according to the data from ionosondes (ionograms), include critical frequencies fоF2, foE, and foEs; the degree of diffuseness of signals; the presence of lateral reflections; the multihop pattern of vertical-incidence ionospheric sounding (VIS); the effect of blocking signal reflections from the F2 layer by the Es layer; and the presence of М-type modes. The analysis was based on the data from ionosondes at low-latitude stations in Athens, Greece, and Nicosia, Cyprus. The following results were obtained. The spring storm was characterized by the presence of lateral reflections, greater diffuseness in the F2 layer, and an increased number of reflections during VIS during daytime hours compared to nighttime hours. The summer storm was characterized by very frequent appearance of sporadic Es layers, the occurrence of М-type reflections, and the effect of blocking. The specific analysis of the winter storm shows that the thick Es layer stretched along the Earth’s surface over a distance of no less than 800 km and had a lifetime of about 7 h.

Influence of Horizontal Ionosphere Nonuniformity on the Spatial Distribution of Ultralow-Frequency Magnetic Fields from Ground-Based Sources

A significant difference was found in the amplitude and polarization spectra of ULF magnetic noise at stations with a base of 120 km during periods of absence of regional thunderstorm activity. A simultaneous analysis of low-frequency data and ionosonde data allowed us to conclude that the difference in the main parameters of the polarization spectrum at two stations is due to the appearance of sporadic Es layers having a nonuniform horizontal intensity distribution with characteristic scales of the order of the base between stations. A difference in the depth of variations in the polarization parameter e was also found during the ionosphere recovery after magnetic storms. It could be related with Es layers, which had not only a nonuniform intensity distribution, but were also located at different altitudes. A difference was found in the frequency scales of the spectral resonance structure during recording of time variations of its fundamental frequencies. Numerical calculations of the parameter e with specifying model Es layers and electron-density profiles corrected at the altitudes of the ionospheric F layer adequately explained the observed difference in the magnetic noise spectra and allowed us to determine the altitudes at which the horizontal ionospheric irregularity existed. The studies were carried out on the basis of records of horizontal magnetic components at Radiophysical Research Institute midlatitude observatories Novaya Zhizn (56° N, 45.74° E) and Staraya Pustyn (55.66° N, 43.63° E, 120 km east of the first reception point).

Fast Ionospheric Dynamics during a Substorm from Vertical and Oblique Sounding Data

Synchronous studies have been conducted on the high-latitude ionosonde at Sodankyula station and the low-latitude ionosonde in Cyprus Island, as well as on two radio paths (the Sodankyula–Gor’kovskaya subauroral and Cyprus–Gor’kovskaya midlatitude paths) during the intense substorm of February 14, 2011. Fast processes (within 5–10 min) have been identified according to vertical sounding at Sodankyula station: sporadic Es layers with an inclined track, multilayer tracks in Es layers, anomalous spreadF, well-expressed layers in diffuse F formations, rapid changes in the peak observed frequencies in the Es layer, and multijump Es reflections of signals. During the substorm, the sporadic Es layers and diffusion in the ionospheric F2 layer are the most stable. The data from vertical sounding at Sodankyula station and oblique sounding on the Sodankyula–Gor’kovskaya track have been found to agree qualitatively. The distance between Sodankyula station and the reflection point of the Sodankyula–Gor’kovskaya path is 400 km in the southern direction. Thus, the ionospheric processes during the substorm are qualitatively close, within 400 km. However, there is a difference between the vertical and oblique sounding data and the data from oblique sounding on the Gor’kovskaya–Cyprus track with a reflection point near the city of Chișinău.

Features of the HF Signal Propagation on Oblique Sounding Paths During Solar and Magnetic Activity in September 2017

We present the results of studying the influence of solar and magnetic activity in September 2017 on the HF signal characteristics on subauroral and midlatitude paths. A connection between the ionospheric effects caused by the magnetic storm and the magnetic disturbance intensity is established. It is shown that the formation of a strong sporadic Es layer in the auroral ionosphere during a magnetic storm makes it possible to use the propagation mode with reflection from Es in the interests of HF communication to neutralize the effects of the negative phase of the storm and absorption growth when unfavorable conditions for the F-mode propagation with reflection from the upper ionosphere occur.

Observed and Calculated Ionograms of Oblique Ionospheric Sounding on HF Radio Paths During a Magnetic Storm of September 7–8, 2017

Ionograms of the oblique ionospheric sounding radio paths Cyprus—Lovozero and Lovozero—Gor’kovskaya (near St. Petersburg) are analyzed using magnetometers and riometers. The behavior of the maximum observed frequencies (MOF) of the F2 and Es layers during a magnetic storm of September 7–8, 2017 is considered. The storm has a specific, not classical form and can be divided into two parts, namely, the first and the second storms. The main results are as follows. 1) The manifestation of the first storm is accompanied by a significant increase in absorption and frequent absence of signals on the paths. The second storm is characterized by increased values of MOF-Es and the presence of signals. 2) The signals on the midlatitude Cyprus—Lovozero path propagate both as 1F2, 2F2, and 3F2 modes and as 2Es and 3Es modes. 3) On the subpolar Lovozero—Gor’kovskaya path, during the disturbance, the signals mainly propagate via reflection from the sporadic Es layer of very high intensity. 4) Modeling of the propagation of HF radio waves using the IRI-2016 model adapted to the vertical sounding data made it possible to match the model ionograms with the real oblique sounding ionograms, including the cases of presence of the M and N modes, as well as triplets, in both quiet and disturbed conditions, which is a new result.

Single-Station Location of Radio Emission Sources in the Decameter Wavelength Range Using a Wide-Aperture Direction Finder and a Chirp Ionosonde–Radio Direction Finder

We present the results of single-station location of radio emission sources on the mid-latitude Vasil’sursk—Rostov-on-Don path using a wide-aperture direction finder and a chirp ionosonde–radio direction finder. Methods for determining the arrival angles under conditions of multipath reception of radio signals are described. It is shown that when single- and double-hop propagation modes are separated by different direction-finding techniques, deviations of the arrival angles reach 5° in the azimuthal plane and up to 10◦ in the elevation plane, which is due to the traveling ionospheric disturbances. It is established that under conditions of a sporadic Es layer, the chirptransmitter azimuth with averaging over frequency and sounding sessions can be determined to an accuracy of 0.1°. When regular 1F and 2F propagation modes are used to estimate the chirptransmitter azimuth, the average errors are 0.5° and 1°–2°, respectively. An algorithm for solving the inverse problem, by which the coordinates of the radio emission sources can be determined from the arrival angles using both the IRI-2012 ionospheric prediction model and correction of the data from the vertical sounding station at the reception point, have been developed. It is shown that the average error in determining the range to radio emission sources is 13%.

Sporadic E S Layers at High Latitudes During a Magnetic Storm of March 17, 2015 According to the Vertical and Oblique Ionospheric Sounding Data

We consider the behavior of the parameters of the ionospheric E s layers according to the vertical sounding at the Sodankyla observatory and oblique sounding at the Lovozero (Murmansk region)—Gor’kovskaya station (Leningrad region) path during a superstorm of March 17, 2015. Temporal and spatial behavior of these parameters is compared. It was found that the storm significantly distorted the normal course of variations of the sporadic E s layer characteristics. Specific behavior of the layers during a storm at points separated by about 300 km was detected. With the help of ray tracing calculations using the IRI model, oblique sounding ionograms were constructed for the radio path analyzed. Primary attention is given to the maximum usable frequency of the F 2 layer—MUF-F 2. Additionally, for the disturbed conditions where there is only a high-power E s layer on the experimental ionograms, the values of MUF-E s and the ratio K =MUF-E s/f o E s for various cutoff frequencies f o E s of the E s layer and its altitudes $$ {h}_{E_s} $$ are calculated within the framework of the well-known approximations. Calculations for the case of weak disturbance and semitransparent E s layers are carried out with the IRI model adapted to the current diagnostics parameters. It was found that the calculated and experimental values of MUF-F 2 are close to each other or coincide, while this cannot be said about MUF-E s. The calculated and experimental values of MUF-E s can be matched in the model of mirror reflection from a flat layer for intense layers and the model of the E layer for thick E s layers of low intensity.

Impact of a Strong Magnetic Storm and Two X-Ray Flares on the Ionospheric HF Channel in the Summer Solstice of 2015 According to Oblique Sounding in the Eurasian Region

We present the results of observations of the impact a strong magnetic storm and two X-ray flares in the summer solstice of 2015 on the HF signal characteristics during oblique sounding of the ionosphere in the Eurasian region. It was found that the negative phase of the magnetic storm led to a strong degradation of the ionospheric channel, up to a long blackout on the paths adjacent to the subauroral latitudes. On the midlatitude paths, a decrease in the maximum observable frequency of the F layer reached 50% with respect to the average values for an undisturbed ionosphere. The propagation velocity of the negative phase of a disturbance from the subauroral to the midlatitude ionosphere is determined (it is equal to about 100 m/s). It is shown that during a magnetic storm the least observable frequency and the average signal-to-noise ratio for the propagation mode via the sporadic E s layer correlate well with the auroral AE index. Anomalous signals were detected in the main phase of the magnetic storm on the Cyprus—Rostov-on-Don path when a chirp ionosonde–radio direction finder was operated in the over-the-horizon HF radar mode. On the basis of modeling and comparison with experimental data, it is shown that the anomalous signals are due to scattering of radio waves by small-scale irregularities located in the subauroral ionospheric F region.

Sporadic potassium layers and their connection to sporadic E layers in the mesopause region at Beijing, China

A double-laser beam lidar to measure potassium (K) layer at Beijing (40.5° N, 116.2° E) was successfully developed in 2010. The parameters of sporadic Ks layers and their distributions were given. The seasonal distribution of Ks occurrence frequency was obtained, with two maxima in July and January. The seasonal distributions of sporadic Es layer occurrence frequency over Beijing differ from those of Ks. However, the good correlation between Es and Ks in the case-by-case studies supports the mechanism of neutralization of metal ions in a descending Es layer.

Impact of heliogeophysical disturbances on ionospheric HF channels

The article presents the results of the observation of a strong magnetic storm and two X-ray flares during the summer solstice in 2015, and their impact on the HF signals characteristics in ionospheric oblique sounding. It was found that the negative phase of the magnetic storm led to a strong degradation of the ionospheric channel, ultimately causing a long blackout on paths adjacent to subauroral latitudes. On mid-latitude paths, the decrease in 1FMOF reached ∼50% relative to the average values for the quiet ionosphere. It is shown that the propagation conditions via the sporadic Es layer during the magnetic storm on a subauroral path are substantially better than those for F-mode propagation via the upper ionosphere. The delay of the sharp decrease in 1FMOF during the main phase of the magnetic storm allowed us to determine the propagation velocity of the negative phase disturbances (∼100m/s) from subauroral to mid-latitude ionosphere along two paths: Lovozero – Yoshkar-Ola and Cyprus – Nizhny Novgorod. It is shown that both the LOF and the signal/noise ratio averaged over the frequency band corresponding to the propagation mode via the sporadic Es layer correlate well with the auroral AE index. Using an over-the-horizon chirp radar with a bistatic configuration on the Cyprus – Rostov-on-Don path, we located small-scale scattering irregularities responsible for abnormal signals in the region of the equatorial boundary of the auroral oval.

Спорадические калиевые слои и их связь со спорадическими Е-слоями в области мезопаузы над Пекином (Китай)

A double-laser beam lidar to measure potassium (K) layer at Beijing (40.5° N, 116.2° E) was successfully developed in 2010. The parameters of sporadic Ks layers and their distributions were given. The seasonal distribution of Ks occurrence frequency was obtained, with two maxima in July and January. The seasonal distributions of sporadic Es layer occurrence frequency over Beijing differ from those of Ks. However, the good correlation between Es and Ks in the case-by-case studies supports the mechanism of neutralization of metal ions in a descending Es layer.

Effect of the Ionospheric Parameter Variations at Altitudes of 80–350 km on Diurnal Dynamics of the ULF Magnetic Field Spectra at Midlatitudes

We study the causes of sporadic and long-term variations in the polarization spectrum of the ultralow-frequency (ULF) magnetic background noise at midlatitudes. Data records of low-frequency horizontal magnetic components at the Novaya Zhizn midlatitude observatory of the Radiophysical Research Institute (56°N, 45.74°E) and the Japanese station Moshiri (44.37°N, 142.27°E) were used. Ionosonde data from the sites located in Russia (Vasilsursk station) and in Japan (Wakkanai station) were also analyzed. The effect of the sporadic Es layers on the frequency spectrum of noise polarization was detected. It is shown that the appearance of quite intense sporadic Es layers with the cutoff frequencies f0Es > 3–5 MHz can significantly alter the polarization spectrum parameters, which is due to variations in the optical depth and Q factor of the sub-ionospheric Alfven resonator (sub-IAR) formed by the valley between the E and F regions. Numerical simulation of the polarization parameters of the background noise using the IRI-2012 model corrected by the ionosonde data confirmed that the Es layer about 5 km thick, with the cutoff frequencies f0Es > 3–5 MHz, may lead to a sharp decrease in the boundary frequency fb between the frequency ranges of the left- and right-hand polarized noise, or even to a complete disappearance of the sub-IAR manifestation in the polarization parameter spectrum. Numerical calculations have also revealed the impact of the altitude position of the Es layer on the Q factor of the sub-IAR. The effect of variations in the altitude and cutoff frequency of the F-layer maximum, as well as the electron density at the altitudes of the E layer and the valley, on the features of the diurnal dynamics of the ULF noise polarization spectra is discussed.

Anomalous phenomena on HF radio paths during geomagnetic disturbances

We analyze ionospheric oblique sounding data on three high-latitude and one high-latitude–midlatitude HF radio paths for February 15 and 16, 2014, when two substorms and one magnetic storm occurred. We investigate cases of anomalous propagation of signals: their reflection from sporadic layer Es, lateral reflections, type “M” or “N” modes, the presence of traveling ionospheric disturbances, and the diffusivity of signals and triplets. The most significant results are the following. In geomagnetically undisturbed times, sporadic Es-layers with reduced maximum observed frequencies (MOFEs) on three high-latitude paths were observed in both days. The values of MOFEs during disturbances are large, which leads to the screening of other oblique sounding signals reflected from the ionosphere. On all four paths, the most frequently traveling ionospheric disturbances due to the terminator were observed in quiet hours from 03:00 to 15:00 UT on the first day and from 06:00 to 13:00 UT on the second day of the experiment. In addition, both the sunset terminator and the magnetic storm on the high-latitude–mid-latitude path were found to generate traveling ionospheric disturbances jointly. No such phenomenon was found on high-latitude paths.