Increase In Geomagnetic Activity Research Articles

MODELING OF SPATIAL-TEMPORAL VARIATIONS OF PHYSICAL PROCESS PARAMETERS IN THE IONOSPHERIC PLASMA OVER UKRAINE DURING THE MAXIMUM PHASE OF THE 24-TH SOLAR ACTIVITY CYCLE (2012—2015)

The object of research is physical processes occurring in the ionospheric plasma. The subject of research: spatial-temporal variations of the main parameters of the ionospheric plasma, which were obtained using incoherent scatter radar. Research methods include the ground-based radiophysical method of incoherent scatter of radio waves, statistical analysis of observation results, and semi-empirical modeling of parameters of dynamic and thermal processes. Modeling and analysis of spatial-temporal variations of the dynamic and thermal processes parameters in the ionosphere during the maximum phase of the 24th solar activity cycle (2012—2015) have been performed using experimental data obtained by the Kharkiv incoherent scatter radar. For the periods of the equinoxes and solstices, diurnal dependences of process parameters in the ionospheric plasma at altitudes from 210 to 450 km were constructed. The values of plasma transfer velocity due to ambipolar diffusion, the density of the full plasma flux, and the flux of charged particles due to ambipolar diffusion were determined. The values of the energy supplied to the electron gas, the density of the heat flux transferred by electrons from the plasmasphere to the ionosphere, as well as the velocity of the equivalent neutral wind and the meridional component of the neutral wind velocity, were calculated. It was established that for the considered periods, the effects of space weather variations and geomagnetic activity were significantly manifested in variations of the plasma flux density due to ambipolar diffusion, the density of the full plasma flux, as well as the energy supplied to electrons per unit time. Quantitative and qualitative characteristics of these parameters were typical but changed significantly (by 2…3 times) in some cases, even with a slight increase in geomagnetic activity.

Responses of the wintertime auroral E-region neutral wind to varying levels of geomagnetic activity

Introduction: The auroral E-region is an important interface where forces from the magnetosphere and the lower atmosphere converge and have a significant effect on the vertical structure of the neutral winds. The resulting vertical neutral wind structure has been reported to be associated with altitude-dependent and nonlinear effects from different forces. We conduct a statistical examination of the reactions of wintertime neutral winds to four various degrees of geomagnetic activity, with a focus on the impacts of ion drag.Methods: We derive neutral winds using the PFISR measurements covering 2010–2019 and will give a statistical view of the auroral E-region neutral wind with a focus on the winter nighttime during different disturbed conditions. We investigate the effects of the geomagnetic activity on the neutral winds and the tidal components by dividing the dataset into 4 subsets. Tidal decomposition is conducted by least square fitting of the seasonal median winds to obtain the mean, diurnal amplitude, diurnal phase, semidiurnal amplitude, and semidiurnal phase.Results and discussion: We find that 1) when geomagnetic activity increases, dawn-dusk asymmetry exists in both zonal and meridional winds in the upper E-region with stronger zonal wind in the dusk sector than in the dawn sector and much stronger meridional wind in the dawn sector than in the dusk sector. 2) Tidal decomposition results reveal that geomagnetic activity has more significant effects on the meridional diurnal amplitude than zonal diurnal amplitude while the zonal and meridional semidiurnal amplitudes show similar changes when the geomagnetic activity increases. In addition, the maximum semidiurnal amplitude, particularly in the zonal direction, appears at a higher altitude with larger values as geomagnetic activity increases, indicating an ascending transition altitude for the semidiurnal oscillations. The ascending trend of maximum semidiurnal amplitude appearing at higher altitudes during more disturbed conditions has not been reported before. 3) Zonal wind over 110 km demonstrates increasing ion drag effects in the evening sector and the effects of coupled ion drag and other factors after midnight.

Correlation of Short-Period Wave Disturbances of the Peak Electron Density of the F2 Layer and the Total Electron Content in the Ionosphere

Correlation analysis of short-period (periods less than 24 h) wave disturbances of the maximum electron density in the F2 layer (NmF2) and the total electron content (TEC) was analyzed based on the data of the vertical ionosonde sounding and receiver of the Global Navigation Satellite Systems operating in Irkutsk. The measurement data in the period 2003–2020, which included almost two solar cycles, have been processed. It was found that the most likely case is a high positive correlation of short-period NmF2 and TEC disturbances. The number of cases of strong positive correlation increases (from 53 to 66%), and the number of cases of positive and negative weak correlation decreases (from 46 to 33%) as the solar and geomagnetic activity increases. During strong geomagnetic storms, the highest correlation (up to R = 0.89) is observed in the main phase of the storm and then decreases in the recovery phase to negative R values. Possible physical mechanisms of the results are considered.

Properties of the Variability of the Maximum Density of the F2-Layer
 over Almaty at Different Levels of Solar and Geomagnetic Activity

The properties of the variability of the maximum density of the F2-layer Nm at different levels ofsolar and geomagnetic activity have been analyzed based on hourly data of the Almaty station (43.2° N, 104° E)for 1958–1988. The standard deviation σ(x) of the fluctuations of Nm relative to the quiet level(x = (Nm/Nm0 – 1) × 100, %) and the average shift of these fluctuations xave are used to characterize thisvariability. In this path, an empirical model of the F2-layer maximum density Nm0 for low geomagnetic activityhas been created. It has been found that the variability of Nm depends weakly on the level of solar activity.The dependence of the variability of Nm on geomagnetic activity is one of the main ones, along with thedependences of this variability on time of day and season. In general, the variance σ2(x) is smaller for quietconditions than for periods of high geomagnetic activity. However, during periods of high geomagnetic activity,a further increase in geomagnetic activity does not lead to an increase in the variance σ2(x). The saturationin the increase in the variance σ2(x) against the background of a continuing increase in geomagnetic activityand the absence of this saturation for the average shift xave seems to be a stable property of the variability ofthe mid-latitude ionosphere during periods of geomagnetic storms. This conclusion is based on an additionalanalysis of ionospheric variability according to data from the Irkutsk and Yamagawa stations, which arelocated about 10 degrees north and south of Almaty station, respectively.

The Densities and Compositions of Background Cold Ions Based on the Van Allen Probe Observations

AbstractThe cold ions, which are generally “invisible” to most instruments, have strong impacts on plasma wave and magnetic reconnection. Under particular situations, these cold ions could be accelerated and thus become detectable. In this study, we statistically investigated the properties of background cold ions based on Van Allen Probe observations. The cold ions could often be detected near the dusk sector, and a clear dawn‐dusk asymmetry is observed for all ion species with higher density at the dusk side, showing plasmaspheric plume‐like structures. Similar to the cold electrons, cold proton ions show a clear boundary of plasmapause with its location moving toward the Earth as geomagnetic activity increases. Furthermore, the percentage of oxygen increases, and the percentage of protons decreases as geomagnetic activity increases whereas the helium composition is generally small. Our results provide important information on ion compositions for the understanding of cold‐plasma dynamics in the inner magnetosphere.

MODELING OF SPATIAL-TEMPORAL VARIATIONS OF DYNAMIC AND THERMAL PROCESS PARAMETERS IN GEOSPACE OVER UKRAINE DURING THE MINIMUM OF 24-TH CYCLE OF SOLAR ACTIVITY (2009, 2019)

We have performed the modelling of spatiotemporal variations of parameters of dynamic and thermal processes in ionospheric plasma at the phases of the minimum of the 24-th cycle of solar activity according to the Kharkiv radar of incoherent scattering. The diurnal dependences of parameters of the processes in the ionospheric plasma at altitudes from 210 to 450 km are constructed for typical geophysical periods (vernal and autumn equinoxes, summer and winter solstices). In the paper, the analysis of spatial and temporal variations of parameters of dynamic and thermal processes in the ionosphere is presented. We determined the value of the plasma transfer velocity due to ambipolar diffusion, the density of the full plasma flux, and the flux of charged particles due to ambipolar diffusion, the value of the energy supplied to the electron gas, the density of the heat flux transferred by electrons from the plasmasphere to the ionosphere, as well as the velocity of the equivalent neutral wind, and the meridional component of the neutral wind velocity. We found that weak variations in space weather do not lead to significant changes in spatiotemporal variations of the parameters of dynamic and thermal processes in the ionosphere for most of the studied periods. Quantitative and qualitative characteristics of most of these parameters and their diurnal variations were typical for the considered seasons. On the contrary, the velocity of the equivalent neutral wind changed significantly (up to 2—2.5 times) even with a weak increase in geomagnetic activity. The reasons for such changes may be the strengthening of horizontal thermospheric winds and the penetration of zonal magnetospheric electric fields into midlatitudes during the equinoxes. The obtained results of calculations can be used in basic studies of solar-terrestrial relations and geospace, for the solution of applied problems related to the ability to predict the state of space weather, as well as for further development of the regional ionosphere model CERIM IION. The object of research: physical processes in the ionospheric plasma. The subject of research: spatiotemporal dependences of the main parameters of ionospheric plasma, which were obtained using incoherent scattering radar. Research methods — terrestrial radiophysical method of incoherent scatter of radio waves, statistical analysis of observation results, semi-empirical modelling of parameters of dynamic and thermal processes.

Global Occurrence of Higher‐Bands ECH Waves in Radiation Belts Based on a Novel Noise Reduction Algorithm (NORA)

AbstractElectrostatic electron cyclotron harmonic (ECH) waves which can efficiently produce scattering loss of electrons, are frequently observed in the first band. Here we present new results on the global occurrence of higher‐band ECH waves in the radiation belts from Van Allen Probes data. We develop a novel noise reduction algorithm which can be widely applied to various plasma waves to better identify naturally occurring waves during periods of instrument interference. The occurrence rate of ECH waves in higher harmonic bands is comparable to that in the first harmonic band, except in the noon‐to‐dusk sector. As the level of geomagnetic activity increases, ECH waves in all bands can be observed at lower L‐shells. The occurrence rates of weak (moderate, strong) waves in all four bands increase 3–4 (4–6, 5–10) times during disturbed periods compared to those during quiet periods. The current results may provide better understanding of ECH‐driven magnetosphere‐ionosphere coupling.

A Statistical Study of Ion Upflow during Periods of Dawnside Auroral Polarization Streams and Subauroral Polarization Streams

We have investigated the effect of the dawnside subauroral polarization stream (SAPS) and dawnside auroral polarization stream (DAPS) on the ionospheric ion upflow in the Northern Hemisphere by using four years of Defense Meteorological Satellite Program (DMSP) observations. The occurrence rate of DAPS is higher than that of dawnside SAPS. Obvious ion upflow occurs in the topside ionosphere around the DAPS region. The effect of the dawnside SAPS on the vertical flow is weakened when geomagnetic activity increases. There are prominent upflow fluxes around the DAPS, while there are insignificant upflow fluxes around the SAPS region. The plasma density trough during SAPS periods becomes shallower with increasing magnetic activity. These variations with magnetic activity might be due to the weakened ion-neutral collision heating efficiency during highly disturbed periods. There is no obvious plasma density trough or ion temperature drop around the DAPS region at the altitude of ~800 km. The ion temperature around the SAPS area decreases, while the electron temperature increases around the DAPS and SAPS regions.

Average characteristics of high-energy magnetospheric electron flux enhancements and the parameters of near-Earth and interplanetary medium in 1987–2021

ABSTRACT Based on the data of 35-yr (1987–2021) measurements of magnetospheric electron fluxes with energy >2 MeV in geostationary orbits, solar wind speed, and geomagnetic activity, a catalogue of electron flux enhancements was compiled in which the electron fluence exceeds 108 cm–2 sr–1 d–1. The epoch superposition method performed using the GOES-13 spacecraft data shows that large electron flux enhancements are preceded by a significant increase in the solar wind velocity and the Ap index of geomagnetic activity, and immediately before the increase the relativistic electron flux decreases. For the events of the catalogue, the average characteristics of electron flux enhancements and parameters of the interplanetary and near-Earth medium were calculated: the mean values of the diurnal and total fluences during an event and the average duration of electron enhancements. The average duration of the electron flux enhancement is 5 d, and the maximum duration is 24 d. Based on the calculated mean values of the electron fluences, solar wind velocity, and Ap-index of geomagnetic activity on the day of electron enhancement and on previous days, a typical behaviour of these parameters during and before an electron flux enhancement was obtained. The average characteristics of electron flux enhancements and the parameters of interplanetary and near-Earth medium are calculated before large electron flux enhancements, when the fluence exceeds 3 × 108, 5 × 108, and 109 particles cm–2 sr–1 d–1, respectively. It is shown that the greater the increase in solar wind velocity and geomagnetic activity the larger the subsequent electron flux enhancement.

Responses of intermediate layers to geomagnetic activity during the 2009 deep solar minimum over the Brazilian low-latitude sector

Abstract. This work presents the daytime behavior of the intermediate layer (ILs) parameters (the virtual height – h'IL, and the top frequency – ftIL) over the low-latitude region of Cachoeria Paulista (CP, 22.42∘ S; 45∘ W, I: −34.59∘) during the 2009 deep solar minimum. Under such a unique condition, this research reveals the ILs' quiet state seasonal behavior as well as its responses to moderate changes in the geomagnetic activity. The main results show that even small variations of geomagnetic activity (quantified by the planetary Kp index) are able to modify the dynamics of the ILs parameters. For the first time, it was observed that during the summer, the h'IL decreases rapidly with the increase of geomagnetic activity, mainly in the early morning hours, while in the following hours, a smoothed rise of the IL was found in all seasons analyzed. Regarding the IL frequency, it was observed that after 12:00 LT, there is a tendency to decrease with the increase of magnetic disturbances, this characteristic being more intense after 16:00 LT for summer and winter. For the equinox, such variation was detected, however with half of the amplitude of the other seasons. In addition, the domain of the annual periodicity of the ftIL stands out, while the h'IL presents a semiannual component under the condition of geomagnetic quiet.

Channeling of Auroral Kilometric Radiation During Geomagnetic Disturbances

The electromagnetic fields measured on the ERG satellite are presented and their comparative analysis with measurements on the WIND satellite is carried out. The possibility of capturing auroral kilometric radiation (AKR) into plasma channels, which was first discovered on the ISEE satellite, has been confirmed. Plasma inhomogeneities, formed with an increase in geomagnetic activity, are extended along the magnetic field and form channels along which the radiation propagates. The trapped radiation spectrum is distorted because of the relative position of the source and channel at low frequencies. The distortion of the AKR spectrum at high frequencies is related to the frequency dependence of propagation conditions in the channel. Asymmetry of the processes of formation of plasma channels and AKR sources in the northern and southern auroral regions is found.

Galileo E5 AltBOC Signals: Application for Single-Frequency Total Electron Content Estimations

Global navigation satellite system signals are known to be an efficient tool to monitor the Earth ionosphere. We suggest Galileo E5 AltBOC phase and pseudorange observables—a single-frequency combination—to estimate the ionospheric total electron content (TEC). We performed a one-month campaign in September 2020 to compare the noise level for different TEC estimations based on single-frequency and dual-frequency data. Unlike GPS, GLONASS, or Galileo E5a and E5b single-frequency TEC estimations (involving signals with binary and quadrature phase-shift keying, such as BPSK and QPSK, or binary offset carrier (BOC) modulation), an extra wideband Galileo E5 AltBOC signal provided the smallest noise level, comparable to that of dual-frequency GPS. For elevation higher than 60 degrees, the 100 s root-mean-square (RMS) of TEC, an estimated TEC noise proxy, was as follows for different signals: ~0.05 TECU for Galileo E5 AltBOC, 0.09 TECU for GPS L5, ~0.1TECU for Galileo E5a/E5b BPSK, and 0.85 TECU for Galileo E1 CBOC. Dual-frequency phase combinations provided RMS values of 0.03 TECU for Galileo E1/E5, 0.03 and 0.07 TECU for GPS L1/L2 and L1/L5. At low elevations, E5 AltBOC provided at least twice less single-frequency TEC noise as compared with data obtained from E5a or E5b. The short dataset of our study could limit the obtained estimates; however, we expect that the AltBOC single-frequency TEC will still surpass the BPSK analogue in noise parameters when the solar cycle evolves and geomagnetic activity increases. Therefore, AltBOC signals could advance geoscience.

FTA: A Feature Tracking Empirical Model of Auroral Precipitation

AbstractThe Feature Tracking of Aurora (FTA) model was constructed using 1.5 years of Polar Ultraviolet Imager data and is based on tracking a cumulative energy grid in 96 magnetic local time (MLT) sectors. The equatorward boundary, poleward boundary, and 19 cumulative energy bins are tracked with the energy flux and the latitudinal position. With AE increasing, the equatorward boundary moves to lower latitudes everywhere, while the poleward boundary moves poleward in the 2300–0300 MLT region and equatorward in other MLT sectors. This results in the aurora getting wider on the nightside and becoming narrower on the dayside. The peak intensity of the aurora in each MLT sector is almost linearly related to AE, with the global peak moving from pre‐midnight to post‐midnight as geomagnetic activity increases. Ratios between the Lyman‐Birge‐Hopfield‐long and ‐short models allow the average energy to be calculated. Predictions from the FTA and two other auroral models were compared to the measurements by the Defense Meteorological Satellite Program Special Sensor Ultraviolet Spectrographic Imagers (SSUSI) on March 17, 2013. Among the three models, the FTA model specified the most confined patterns with the highest energy flux, agreeing with the spatial and temporal evolution of SSUSI measurements better and predicted auroral power (AP) better during higher activity levels (SSUSI AP > 20 GW). The Fuller‐Rowell and Evans (1987) and FTA models specified very similar average energy compared with SSUSI measurements, doing slightly better by ∼1 keV than the OVATION Prime model.

Sustained Oxygen Spectral Gaps and Their Dynamic Evolution in the Inner Magnetosphere

AbstractVan Allen Probes observations of ion spectra often show a sustained gap within a very narrow energy range throughout the full orbit. To understand their formation mechanism, we statistically investigate the characteristics of the narrow gaps for oxygen ions and find that they are most frequently observed near the noon sector with a peak occurrence rate of over 30%. The magnetic moment (μ) of the oxygen ions in the gap shows a strong dependence on magnetic local time (MLT), with higher and lower μ values in the morning and afternoon sectors, respectively. Moreover, we find through superposed epoch analysis that the gap formation also depends on geomagnetic conditions. Those gaps formed at lower magnetic moments (μ < 3,000 keV/G) are associated with stable convection electric fields, which enable magnetospheric ions to follow a steady drift pattern that facilitates the gap formation by corotational drift resonance. On the other hand, gaps with higher μ values are statistically preceded by a gradual increase of geomagnetic activity. We suggest that ions within the gap were originally located inside the Alfven layer following closed drift paths, before they were transitioned into open drift paths as the convection electric field was enhanced. The sunward drift of these ions, with very low fluxes, forms a drainage void in the dayside magnetosphere manifested as the sustained gap in the oxygen spectrum. This scenario is supported by particle‐tracing simulations, which reproduce most of the observed characteristics and therefore provide new insights into inner magnetospheric dynamics.

PSIII-4 Asthenozoospermia in geomagnetic activity

Abstract Reproductive qualities depend on a complex of biotic and abiotic factors. The ejaculate of bulls is characterized by morphological heterogeneity. Pathologies in the structure of each segment or several segments simultaneously may occur under the influence of biotic and abiotic factors. The aim of the study was to study the influence of geomagnetic storm on the occurrence of asthenozoospermia in freshly collected bull sperm. Monitoring of geomagnetic activity in the region of the study was carried out according to the Institute of terrestrial magnetism, ionosphere and radio wave propagation. N. V. Pushkova of the Russian Academy of Sciences.Sperm quality assessment was carried out using the software “Argus-CASA.” A Mackler’s camera was used to assess mobility and concentration. Statistical analysis of the results of the study was carried out using IBM SPSS Statistics 23.0. The slides were visualized using a Nikon Eclipse Ni-U microscope and a Nikon DS-Qi2 camera. A geomagnetic storm with a K-index ≥ 5.0 was recorded four times in the monitoring region during the study period. During the period when the geomagnetic situation was normal (K = 1,0 1.0), the content of sperm with progressive movement (PR – progressive-mobile) was 87±2.3%, it varied from 82% to 91%. The content of sperm with flagella pathology was 5.74±0.12%. With an increase in geomagnetic activity to K-index ≥ 5.0, the content of sperm with non – progressive movement (NP-non-progressive-motile) increased to 14.2% and motionless sperm to 27.8% (IM-motionless). The content of motionless sperm at some individuals was 38%. Cells with multiple morphological anomalies accounted for 34% at some bulls. Asthenozoospermia in the period of geomagnetic activity is accompanied by an increase in the number of cells with flagella pathology, including multiple morphological anomalies. The study was supported by RFBR, project №. 18-016-00128 А

GIMLi: Global Ionospheric total electron content model based on machine learning

EXtreme Gradient Boosting over Decision Trees (XGBoost or XGBDT) is a powerful tool to model a wide range of processes. We propose a new approach to create a global total electron content model, using machine-learning-based techniques, in particular, gradient boosting. The model is based on the Global Ionospheric Maps computed by Universitat Politecnica de Catalunya with a tomographic-kriging combined technique (UQRG). To reduce the problem complexity, we used empirical orthogonal functions (EOFs). The created model involves the first 16 spatial EOFs. For training and validation we used the 1998–2016 data sets, and the 2017 data as a test data set. To drive the model, we used the following features: (1) geomagnetic activity indexes (Kp, Ap, AE, AU, AL) and solar activity indexes (R, F10.7); (2) derivative values from these indexes such as the mean value and standard deviations within the last 12 h, last 11 days, and last 40 days; (3) day of the year (DOY); (4) averaged EOFs for given Kp and UT, and those for a given DOY and UT. The validation data set revealed the following hyperparameters for XGBoost learning: number of trees is 100, tree depth is 6, and learning rate is 0.1. Comparisons with the NeQuick2, Klobuchar, and GEMTEC models show that machine learning achieves higher accuracy for the 2017 test data set. The global averaged root-mean-square errors and mean absolute percentage errors were about 2.5 TECU and 19% for the nonlinear GIMLi-XGBDT model, about 4 TECU and 30–40% for NeQuick2, GEMTEC, and the linear model GIMLi-LM, and about 5.2 TECU and 73% for the Klobuchar model. A 4-fully-connected-layer artificial neural network provided a higher error (3.28 TECU and 27.7%) as compared to GIMLi-XGBDT. For all models mentioned, the error peaked in the equatorial anomaly region. The solar activity increase does not affect the error of the nonlinear GIMLi-XGBDT model. However, an increase in geomagnetic activity strongly affects that model.

Geomagnetic Effects in Spatial Distributions of Particle Precipitation in Terms of Particle Energy Channels

AbstractThis study examines the spatial distributions of precipitation during active and quiet times. Most previous studies commonly classified precipitation into different energy spectral types, but we utilized a classification according to particle energy channels. A general conclusion derived from these distributions suggests that regardless of active and quiet times, low‐energy (<1 keV) and high‐energy precipitating particles are mostly on the dayside and nightside, respectively. A comparison with past results reveals that the high‐energy electron precipitation during quiet times is mostly due to wave scattering and that during active times is mainly produced by quasi‐static potential structures (QSPS) and Alfvénic acceleration, while low‐energy electron precipitation is mostly caused by QSPS and Alfvénic acceleration regardless of quiet and active times. For both high‐energy proton and electron precipitation, the nightside dawn‐dusk asymmetry of their distributions during active times is found to be opposite of that during quiet times. We infer that the distribution of high‐energy precipitation during quiet times is dominated by the curvature and gradient drifts, while during active times it is mainly due to the physical processes or phenomena related to substorms in the magnetotail. Empirical orthogonal function analysis has been applied in this study to derive where the flux has the maximum enhancement as the geomagnetic activity increases. The results further demonstrate that low‐energy and high‐energy protons mainly increase in the noon and postmidnight sectors, respectively. The highest enhancements of low‐energy and high‐energy electrons are in the prenoon and premidnight sectors, respectively.

Investigation of equatorial plasma bubble irregularities under different geomagnetic conditions during the equinoxes and the occurrence of plasma bubble suppression

In this study, we investigated the behavior of equatorial plasma bubble irregularities under different geomagnetic conditions during March 2015 and September 2017. It was used Total Electron Content (TEC) data obtained from SGOC (6,89 oN, 79,87 oE), IISC (12,94 oN, 77,57 oE) and HYDE (17,40 oN, 78,50 oE) receiver stations which located between the trough and the crest of the equatorial ionization anomaly (EIA). We used the Rate of TEC change (ROT) and Rate of TEC change index (ROTI) to represent plasma bubbles irregularities. These indices are a well proxy for the ionospheric fluctuations and can be used to describe features of plasma bubbles irregularities. The equatorial plasma bubble irregularities for all stations were observed between 13 UT and 20 UT (during postsunset period) during equinoxes. The intensity level of ROTI during postsunset periods was greater than 1 TECU min−1. Also, the values of mean ROTI (ROTIave) between 13 UT and 20 UT have values greater than 0,4 TECU min−1 while the values of ROTIave at the other hours have values less than 0,4 TECU min−1. The geomagnetic activity has a significant effect on the occurrence of equatorial plasma bubbles irregularities. The occurrence rate of equatorial plasma bubble irregularities observed during postsunset hours increased as geomagnetic activity increases. It also was observed that the main phases of geomagnetic storms have the triggering effect of storms on equatorial plasma bubble irregularities observed at postsunset hours while the recovery phases of geomagnetic storms have the suppression effect of storms on equatorial plasma bubble irregularities. Asymmetry between two equinoxes was observed. The occurrence rate of equatorial plasma bubble irregularities in the March equinox was much larger than that of the September equinox. The occurrence probability of equatorial plasma bubbles for March Equinox was maximum with 45,1% at 17 UT while the occurrence probability of equatorial plasma bubbles for September Equinox was maximum with 11,5% at 16 UT. The enhancements and reductions in the latitudinal gradient of VTEC show similar behaviors with the occurrence of equatorial plasma irregularities. The EIA during postsunset hours contributes significantly to the occurrence of equatorial plasma bubbles irregularities.

ДИАМАГНИТНЫЕ ПЛАЗМОИДЫ КАК СОСТАВНАЯ ЧАСТЬ ДИАМАГНИТНЫХ СТРУКТУР МЕДЛЕННОГО СОЛНЕЧНОГО ВЕТРА И ИХ ВОЗДЕЙСТВИЕ НА МАГНИТОСФЕРУ ЗЕМЛИ

We have shown that diamagnetic structures (DSs), which form the basis of the slow quasi-stationary solar wind (SW), are observed in Earth’s orbit as a sequence of DSs of various scales. The analysis of this phenomenon indicates that diamagnetic plasmoids in SW, whose concept was introduced by Karlsson in 2015, are identical to small-scale DSs. We have found that the impact of a sequence of DSs in the slow SW on Earth’s magnetosphere causes an increase in geomagnetic activity. Isolated DSs generate short-term magnetic disturbances whose duration is approximately equal to the DS duration. Hence, a sequence of DSs can cause sawtooth substorms. We emphasize that the interaction of DS in the slow SW under northward interplanetary magnetic field can be associated with penetration of DS high-density plasma into the magnetosphere.

DIAMAGNETIC PLASMOIDS AS PART OF DIAMAGNETIC STRUCTURES OF THE SLOW SOLAR WIND AND THEIR IMPACT ON EARTH’S MAGNETOSPHERE

We have shown that diamagnetic structures (DSs), which form the basis of the slow quasi-stationary solar wind (SW), are observed in Earth’s orbit as a sequence of DSs of various scales. The analysis of this phenomenon indicates that diamagnetic plasmoids in SW, whose concept was introduced by Karlsson in 2015, are identical to small-scale DSs. We have found that the impact of a sequence of DSs in the slow SW on Earth’s magnetosphere causes an increase in geomagnetic activity. Isolated DSs generate short-term magnetic disturbances whose duration is approximately equal to the DS duration. Hence, a sequence of DSs can cause sawtooth substorms. We emphasize that the interaction of DS in the slow SW under northward interplanetary magnetic field can be associated with penetration of DS high-density plasma into the magnetosphere.