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Abstract—

In solar activity, in addition to the 11-year Schwabe cycle, there are also shorter-period oscillations in the range from 27 days to 11 years, which are called mid-term oscillations. In our study, we identify quasi-6-year oscillations in solar activity expressed by the sunspot number SN using wavelet analysis and investigate the characteristics of these variations during 1750–2020. The analysis shows that the ~6-year cycle in SN is a real independent oscillation. A similar quasi-6-year periodicity has been found in the monthly mean records of geomagnetic field components at the Sitka and Honolulu observatories during 1910–2020. It was found that the variations of the geomagnetic field in the range of 5–6-year periods can be caused by the effect of variations in solar activity in the same frequency range. In addition, in the SN series and geomagnetic field variations, a quasi-biennial cycle is well observed, the amplitude of which in some time intervals exceeds the amplitude of the cycle with a period of 5–6 years.

Abstract

Alfvén waves with periods of a few seconds excited in solar coronal magnetic loops during flare energy release can lead to effective heating of the plasma in the lower atmosphere of the Sun, which is responsible for continuous optical radiation. Meanwhile, the question of the propagation time of these modes from the corona to the photosphere has not yet been considered in detail. Based on solar atmospheric model by Avrett and Loeser (2008), for different values of background magnetic fields, taking into account their height dependence, the estimates of the propagation time of Alfvén waves from the corona to the photosphere were obtained. The characteristic values exceeding several minutes and impose certain restrictions on wave heating of the lower atmosphere of the Sun. The implications of the results are discussed.

Abstract—

Since January 2020, the current solar cycle 25 has begun. Its development in the first four years, according to the Gnevyshev–Ohl rule, brought it into the family of medium-sized cycles. In November 2023, it entered the maximum phase. Therefore, the maximum of the current cycle should take place no later than June 2024 with the expected value of the relative number of sunspots W* = 100+/–10 (150+/–15 in the V2 system). The minimum of the current cycle should be expected in the first half of 2031, and the course of its development on the growth branch shows that it fits into the characteristics of average solar cycles of the epoch of lowered solar activity on the growth branch with its own features. This confirms the stability of the scenario of solar cyclicity for the last ~190 years, which provides for a change in the level of sunspot activity in different epochs of solar activity, increased or lowered, with clearly distinguished transition periods, as a consequence of regular changes in the mode of generation of the total solar magnetic field, with a duration of ~5 cycles.

Abstract

The work describes the design of a measurement module (fluxgate compass) and the creation of various magnetometer devices on its basis. These devices are intended for geomagnetic and special works in various conditions and environments both for stationary observation points and for expeditions.

Abstract

Ionospheric sporadic E layers are very thin, but with a much higher electron density than normal E regions that occur at altitudes of about 90–130 km. Vertical wind shear is considered the main source of mid-latitude sporadic E layer formation, which leads to periodicity, such as 24-h, 12-h, and so on. In this paper, a time series analysis of the critical frequency of the sporadic E layer (foEs) observed by an ionosonde is performed at seven stations (spanning about 37° N–51° N and 29° S–67° S) to investigate the terdiurnal signature in it. Except for the already known 24-h and 12-h periodicities features which are related to diurnal and semidiurnal tides, new findings are also obtained. The 8-h periodicity is a regular and repeatable feature at high mid-latitude regions of both hemispheres. The 8-h periodicity is more prominent at mid-latitudes (~50° N and ~60° S) during the winter and spring months of the hemisphere, which agrees with the terdiurnal tide features. It also shows that the amplitude of the 8-h periodicity is equivalent to the 12-h periodicity component in summer and autumn and almost the same as the 24-h periodicity component in winter under certain circumstances. This indicates that the 8-h periodicity should be taken into consideration for sporadic E layer modeling.

Abstract

The impact of the Weddell Sea Anomaly on the structure of the nightside ionosphere in the summer Southern Hemisphere is considered in detail. For this, data from the CHAMP satellite were used in January 2003 under high solar activity and in January 2008 under low solar activity. The data relate to the local time interval 02−04 LT, when the increase in electron density due to the formation of the anomaly is the strongest. At longitudes of 60°−180° E under high solar activity and 0°–210° E under low solar activity, where there is no anomaly, the main ionospheric trough is observed. The plasma peak in the nightside ionosphere associated with formation of the anomaly reaches 6 MHz under low solar activity and 10 MHz under high solar activity. The strongly developed plasma peak decreases sharply to high latitudes at the equatorward boundary of auroral diffuse precipitation, which corresponds to the plasmapause. When the anomaly is weakly developed, the contribution of diffuse precipitation becomes noticeable, so that the plasma peak expands poleward due to this precipitation. Poleward of the anomaly, the high-latitude trough is usually observed at latitudes of the auroral oval. A well-defined electron density minimum is often formed equatorward of the Weddell Sea Anomaly, which can be defined as a subtrough. Sometimes the subtrough is created by the escape of ionospheric plasma from the summer to the winter hemisphere. Then a density maximum forms in the winter hemisphere at adjacent latitudes. A subtrough is much more common under low solar activity than under high.

Abstract

Geomagnetic storms are disorders in Earth’s magnetic field triggered by solar activity. This research attempts to foretell the total electron content (TEC) using the Kriging and AI model in both low and mid-latitude stations during strong geomagnetic storms that happened on March 17, 2015 and February 3, 2022. This research paper focuses on predicting and analysing TEC anomalies in the ionosphere during the solar storm by using three models: ordinary kriging (OK), cokriging (CoK) and recurrent neural network (RNN). The predicted TEC values by the models are justified with the TIEGCM and KMPCA models. Parameters like RMSE, CC, MAE, and MAPE were applied to assess the execution of predictive models and to quantify the accuracy of predictions. The average RMSE for TEC predicted in the low-latitude region ranges from 4.90 to 5.41, 5.85 to 6.26 and 8.50 to 9.90 for the OK, CoK, and RNN models, respectively. Likewise, the average RMSE for TEC predicted in the mid-latitude region ranges from 1.81 to 4.04, 1.91 to 4.24 and 2.77 to 5.38 for the OK, CoK, and RNN models, respectively. The performance evaluation parameters show that the OK performs better than the CoK and RNN models.

Abstract

Here we studied the planetary features of the spatiotemporal distribution of ionospheric electrojets recorded in the onset of a substorm and in time on the activity maximum of three very intense substorms (with an AL-index from –1200 to –1700 nT) observed during the main phase of the strong magnetic storm on March 23−24, 2023. We have analyzed the substorms by applying the global maps of the planetary distribution of high-latitude ionospheric currents, compiled from simultaneous magnetic measurements on 66 low-orbit satellites of the AMPERE project, as well as ground-based magnetograms from the Scandinavian IMAGE profile and mid-latitude IZMIRAN stations located in the same longitudinal region. It was established that the onset of all the studied substorms on the IMAGE meridian was accompanied by the development of a nighttime current vortex with clockwise rotation, which is an indicator of an increase in downward field-aligned currents. The ground-based mid-latitude observations at the IZMIRAN station network confirmed that the center of the current wedge of the substorm was located in the nighttime sector significantly east of the IMAGE meridian. In the time of the substorm intensity maximum, a similar but more extensive current vortex was observed in the morning sector, which is probably typical of intense substorms.

Abstract

The discussion about the origin of the zebra pattern has been going on for more than 50 years. In many papers it is usually postulated that the double plasma resonance mechanism always works in the presence of fast particles in the magnetic trap. Due to a number of difficulties encountered by this mechanism, works on its improvement began to appear, mainly in a dozen papers by Karlický and Yasnov, where the whole discussion is based on variability of the ratio of the magnetic field and density height scales and the assumption of some plasma turbulence in the source. Here we show possibilities of an alternative model of the interaction between plasma waves and whistlers. Several phenomena were selected in which it is clear that the ratio of height scales does not change in the magnetic loop as the source of the zebra pattern. It is shown that all the main details of the sporadic zebra pattern in the phenomenon of August 1, 2010 (and in many other phenomena), can be explained within the framework of a unified model of zebra patterns and radio fibers (fiber bursts) in the interaction of plasma waves with whistlers. The main changes in the zebra pattern stripes are caused by scattering of fast particles by whistlers leading to switching of the whistler instability from the normal Doppler effect to the anomalous one. In the end, possibilities of laboratory experiments are considered and the solar zebra pattern is compared with similar stripes in the decameter radio emission of Jupiter.

Abstract

During the expansion phase of a substorm, the poleward jump of auroras (breakup) and the expansion of the auroral bulge are observed. The expansion is accompanied by a negative magnetic bay under the aurora and a positive magnetic bay at mid-latitudes. The magnitude of the negative bay is characterized by the auroral AL-index. The Mid-Latitude Positive Bay index (MPB-index) was previously proposed in order to characterize the positive bay. In this article, the statistical relationship of the MPB-index with the geomagnetic activity at different latitudes and with the parameters of the solar wind and interplanetary magnetic field is investigated. It is shown that all extremely high values of the MPB-index (above 10 000 nT2) are observed during strong geomagnetic storms (when the Dst-index falls below –100 nT), all extremely strong geomagnetic storms (when the Dst-index falls below –250 nT) are accompanied by extremely high values of the MPB-index. Statistically, the MPB-index increases with increasing geomagnetic activity at any latitude. On average, the MPB-index increases with increasing interplanetary magnetic field magnitudes and any of its components. However, for the Bz-component, large values of the MPB-index are observed at its southward orientation. For the plasma parameters of the solar wind, the MPB-index increases most strongly with the increase of its speed. The dependence on the dynamic pressure and on the value of the EY-component of the electric field of the solar wind is also strong. However, the MPB-index weakly depends on the density and temperature of the solar wind.

Abstract

Ionospheric disturbances that accompanied the moderate magnetic storm on January 14–20, 2022, are analyzed. The work is based on data obtained from vertical and oblique ionospheric sounding in the northeastern region of Russia and supplemented by observations at HF radars and magnetic observatories. It has been revealed that the amplitudes of positive and negative ionospheric disturbances accompanying this storm are comparable to those observed on other days of January during weak magnetic storms and disturbances. The specific features of the disturbances observed only during the storm in question are as follows: (1) a midnight–morning increase in the maximum observed frequency of one-hop mode of HF radio wave propagation on the paths Norilsk–Tory and Magadan–Tory on 14 January; (2) enhancement of nighttime fluctuations of the critical frequency in the F2 layer in Irkutsk and the maximum observed frequency of one-hop mode on the path Magadan–Tory on January 15; and (3) morning–midday Es layers with limiting frequencies reaching 7 MHz that were observed in mid-latitudes at the end of the first day and beginning of the second day of the storm recovery phase.

Abstract

In this work the problem of reconstructing the vector anomalous magnetic field from single-component data was solved by means of artificial neural networks. For training an artificial neural network a database of anomalous magnetic field components \({{B}_{x}}\) , \({{B}_{y}}\) , \({{B}_{z}}\) was created using a set of point magnetic dipoles lying under the field measurement plane. Using a synthetic example, the work of a trained neural network was shown in comparison with a well-known numerical algorithm for restoring a vector field from data of one component. Further, according to the data of the vertical component of the anomalous geomagnetic field the horizontal components of the anomalous geomagnetic field were restored using artificial neural networks in the territory of 58°–85° E, 52°–74° N with a grid step of 2 arc minutes.

Abstract

Events of induced proton precipitations from the inner radiation belt have been detected. They accompanied almost a half (11) of 25 anomalous electron precipitations recorded onboard the Meteor-M No. 2 satellite in 2014−2022 in Oceania at low latitudes in the morning hours of local time under quiet geomagnetic conditions. It is surmised that such events could be provoked by proton fall into cyclotron resonance with low-frequency radiation stimulated by a mobile ionospheric heater. The observed effects in anomalous electron precipitations which may be interpreted in the framework of the mobile ionospheric heater conception are also discussed.

Abstract

The article presents the results of a comparative analysis of the solar proton event on March 30, 2022, which has an unusual time profile of solar proton fluxes, and the previous and subsequent solar proton events (March 28, 2022, and April 02, 2022). Increases in energetic proton fluxes in the interplanetary and near-Earth space are associated with successive solar X-ray flares M4.0, X1.3, and M3.9 and three halo-type coronal mass ejections. The study was based on experimental data obtained from spacecraft located in the interplanetary space (ACE, WIND, STEREO A, and DSCOVR), in a circular polar orbit at an altitude of 850 km (Meteor-M2) and in geostationary orbit (GOES-16, Electro-L2). An explanation has been proposed for the specific features of the energetic proton flux profile in the solar proton event on March 30, 2022: protons accelerated in the flare on March 30, 2022 were partially screened by an interplanetary coronal mass ejection, the source of which was the explosive processes on the Sun on March 28, 2022; late detection of maximum proton fluxes, simultaneous for particles of different energies, is due to the arrival of particle fluxes inside an interplanetary coronal mass ejection. The spatial distribution of solar protons in near-Earth orbit was similar to the distribution at the Lagrange point L1 but with a delay of ~50 min.

Abstract—

Attempts have been made repeatedly to investigate the effect of the geomagnetic activity on the equatorial plasma bubble (EPB) generation. At the moment, it is generally accepted that the geomagnetic activity tends to suppress the EPB generation and evolution in the pre-midnight sector. As for the post-midnight sector, it is believed that the EPB occurrence probability will increase after midnight as the geomagnetic activity increases. Moreover, the growth rates of the EPB occurrence probability will strongly depend on the solar activity: at the solar activity minimum, they will be the most significant. A sufficient amount of the observations is required to confirm these ideas. For this purpose, the EPB observations obtained on board the ISS-b satellite (~972–1220 km, 1978–1979) in the pre- and post-midnight sectors are best suited. The data were considered in two latitudinal regions: the equatorial/low-latitude (±20°) and mid-latitude ±(20°–52°) regions. The LT- and Kp-variations of the EPB occurrence probability were calculated for both groups. (1) It was revealed that the occurrence probability maximum of the EPBs recorded at the equator and low latitudes is observed in the premidnight sector. The EPB occurrence probability decreases with increasing the Kp-index with a delay of 3 and 9 h before the EPB detection. (2) However, the occurrence probability maximum of the EPBs recorded at the mid-latitudes occurs in the post-midnight sector. Their occurrence probability increases slightly with the increase of the Kp-index taken 9 h before the EPB detection. Thus, the idea of the ionospheric disturbance dynamo (IDD) influence on the post-midnight EPB generation has been confirmed. The IDD mechanism “switched on” after some hours of the enhanced geomagnetic activity and favors the generation. However, its influence is weakened during the years of increased solar activity.

Abstract

Positioning, navigation and time are the cornerstones of satellite navigation. These aspects are frequently affected by ionospheric variations caused by solar flares (SF). In this study, we have attempted to predict the range error (RE) caused by ionospheric delay in Global Positioning System (GPS) signals during six different X-class SF that occurred in the 25th solar cycle using two different approaches, namely, a recurrent neural network (RNN) and the ordinary Kriging-based surrogate model (OKSM). The total electron content (TEC) collected from Hyderabad station along with other input parameter includes the Planetary A and K index (Ap and Kp), solar sunspot number (SSN), disturbance storm time index (Dst), and radio flux measured at 10.7 cm (F10.7) were used for prediction. The OKSM uses the previous six days of datasets to predict the RE on the seventh day, whereas the RNN model uses the previous 45 days of datasets to predict the RE on the 46th day. The performance of both models is evaluated using statistical parameters such as root mean square error (RMSE), normalized root mean square error (NRMSE), Pearson’s correlation coefficient (CC), and symmetric mean absolute percentage error (sMAPE). The results indicate that the OKSM performs well in adverse space weather conditions when compared to RNN.

Abstract

The induction and momentum equations are simplified to a dynamical system for the kinetic and magnetic energies in Earth’s core. Stable stationary points of this system give a geomagnetic field of ~10 mT and the cosecant of the angle between the magnetic field vector and fluid velocity vector is on average about 500 at a known speed of ~1 mm/s and a generally accepted dynamo power of ~1 TW. With a generally known typical geomagnetic time on the order of 1000 years, harmonic secular variations on the order of several decades and rapid exponential changes on the order of several months, possibly associated with jerks, were obtained. All this agrees well with dynamo theory, paleomagnetic reconstructions, numerical modeling, and observations. A geomagnetic energy of ~10 mJ/kg is four orders of magnitude greater than the kinetic energy. Under conditions of such dominant magnetic energy, an analytical solution was obtained, which over time converges to stable stationary points. Apparently unlikely catastrophes with virtually zero magnetic energy near partially stable stationary points are discussed.

Abstract

The study estimates the contribution of middle-scale solar wind structures (variations recorded by a spacecraft during ~10 min intervals) in turbulence development in the transition region behind the bow shock. The analysis is based on simultaneous measurements of plasma and/or magnetic field parameters in the solar wind, in the dayside magnetosheath, and on the flanks. The study adopts measurements by Wind, THEMIS, and Spektr-R spacecraft. The properties of the magnetic field and ion flux fluctuation spectra are analyzed in the 0.01–4 Hz frequency range, which corresponds to the transition from MHD to kinetic scales. The dynamics of turbulence properties in the magnetosheath is governed by large-scale disturbances, while structures with smaller scales have an effect in the absence of large-scale structures.

Abstract

The results of identifying trends in the annual average ionospheric indices ΔIG and ΔT are presented, obtained after excluding from IG and T the dependence of these indices on the annual average solar activity indices. The solar activity indices were F10, Ly-α, and MgII—solar radiation fluxes at 10.7 cm, in the Lyman-alpha line of hydrogen (121.567 nm), and the ratio of the central part to the flanks in the magnesium emission band 276–284 nm. Two time intervals (in years) are considered: 1980–2012 and 2013–2023. It was found that in 1980–2012, all analyzed linear trends were negative: the ΔIG and ΔT values decreased over time; they were very weak and insignificant. Fluctuations of ΔIG and ΔT with respect to trends for Ly-α were almost twice as large as for F10 and MgII. In the interval of 2013–2023, all analyzed linear trends intensified and became significant: the rate of decrease in ΔIG and ΔT over time increased. For MgII this rate was almost twice as high as for F10. For 2013–2023, the MgII index overestimated the contribution of solar radiation to ionospheric indices, especially during the growth phase of solar cycle 25, which began at the end of 2019. As a result, in the growth phase of solar cycle 25, the F10 index became a more adequate solar activity indicator for ionospheric indices than MgII. In the interval of 1980–2012, the F10 and MgII indices changed almost synchronously. The growth phase of solar cycle 25 was the first case this synchrony was disrupted for the entire period of MgII measurements.

Abstract

Accurate diagnosis of regional atmospheric and surface energy budgets is critical for understanding the spatial distribution of heat uptake associated with the Earth’s energy imbalance (EEI). This contribution discusses frameworks and methods for consistent evaluation of key quantities of those budgets using observationally constrained data sets. It thereby touches upon assumptions made in data products which have implications for these evaluations. We evaluate 2001–2020 average regional total (TE) and dry static energy (DSE) budgets using satellite-based and reanalysis data. For the first time, a consistent framework is applied to the ensemble of the 5th generation European Reanalysis (ERA5), version 2 of modern-era retrospective analysis for research and applications (MERRA-2), and the Japanese 55-year Reanalysis (JRA55). Uncertainties of the computed budgets are assessed through inter-product spread and evaluation of physical constraints. Furthermore, we use the TE budget to infer fields of net surface energy flux. Results indicate biases < 1 W/m2 on the global, < 5 W/m2 on the continental, and ~ 15 W/m2 on the regional scale. Inferred net surface energy fluxes exhibit reduced large-scale biases compared to surface flux data based on remote sensing and models. We use the DSE budget to infer atmospheric diabatic heating from condensational processes. Comparison to observation-based precipitation data indicates larger uncertainties (10–15 Wm−2 globally) in the DSE budget compared to the TE budget, which is reflected by increased spread in reanalysis-based fields. Continued validation efforts of atmospheric energy budgets are needed to document progress in new and upcoming observational products, and to understand their limitations when performing EEI research.