Periods Of Geomagnetic Activity Research Articles

COMPARATIVE ANALYSIS OF MAGNETIC STORMS IN THE ODESSA MAGNETIC ANOMALY REGION WITH PLANETARY AND IONOSPHERIC STORMS DURING THE MONITORING PROGRAM AT RT "URAN-4" (1987 – 2010)

This work is a continuation of the study of the response of the Odesa geomagnetic anomaly to the manifestations of solar and planetary geomagnetic activity. Not far from the territory of this magnetic anomaly there is the geomagnetic observatory "Odesa" and the decameter radio telescope "URAN-4" of the RI NASU. A catalogue of magnetic storms for the period 1987-1994 and 2000-2009 was compiled for the monitoring program of high-power space radio sources at RT "URAN-4" using the database of the geomagnetic observatory "Odesa". In this paper, a comparative analysis of the features of the manifestations of geomagnetic storms in the zone of the Odesa magnetic anomaly, planetary storms and ionospheric storms in the 22nd and 23rd cycles of solar activity is carried out. The main results are as follows. The magnetic anomaly amplifies the effects of regional manifestations of planetary magnetic storms. The number of different types of magnetic storms and the dynamics of their changes in the Odesa anomaly differ significantly in the 22nd and 23rd cycles of solar activity. Comparisons have shown that the duration of magnetic storms in the Odessa anomaly is longer than the duration of planetary magnetic and ionospheric storms. According to the data of the «URAN-4» radio telescope, geomagnetic storms form various manifestations of the effects of ionospheric flickers and flux changes for space radio sources depending on the time of their observations. For the region of the Odesa geomagnetic anomaly, such comprehensive studies have not been carried out before. The conducted studies will become an important basis for understanding the influence of magnetic anomalies on the dynamics of the ionosphere during periods of solar and geomagnetic activity.

Assessing the performance of IRI-2016 and IRI-2020 models using COSMIC-2 GNSS radio occultation TEC data under different magnetic activities over Egypt

Abstract Variations in Total Electron Content (TEC) between the COSMIC-2, IRI-2016, and IRI-2020 are considered under different levels of geomagnetic storm activity: minor, moderate, and severe. TEC values are scrutinized at three levels of the Kp index, which serves as a metric for gauging the strength of a magnetic storm (Kp = 3.0, Kp = 6.0, Kp = 8.0) and across four-time intervals throughout 24 h to understand the performance of the models during both day and night-time conditions. Statistical analysis reveals that the standard deviation of TEC variations is lower during minor storms than moderate and severe. The comparison of variations between COSMIC-2 Radio Occultation TEC and both IRI-2016 and IRI-2020 models revealed more substantial discrepancies during day-time intervals; This was likely attributed to the dynamic and complex nature of the ionosphere influenced by solar radiation and other factors. Comparative analysis across the three levels of storm activity demonstrated that IRI2020 provided improved results over IRI2016, particularly during minor geomagnetic storm events. The study demonstrates that IRI2020 is more accurate than IRI-2016 at forecasting ionospheric conditions, especially at night and during moderate geomagnetic storm activity periods. Both models, however, provide valuable insights during challenging space weather conditions, and the results demonstrate their utility in understanding and forecasting the ionosphere’s behavior. The results yield valuable insights into space weather conditions and their effects on technology and communication, highlighting the potential for further improvement in TEC prediction models.

Evaluation of telluric-associated corrosion on buried pipelines

Telluric currents, often known as geomagnetically induced currents (GIC), are produced by the natural variations of the Earth's magnetic field.The corrosion protection system of a buried pipeline generally comprises the coating and cathodic protection system. Cathodic protection is an electrochemical protection system that maintains the pipe-to-soil potential (PSP) sufficiently negative in order to reduce corrosion to negligible levels. Varying telluric currents alter the PSP, thus interfering with the pipeline corrosion protection system and can create conditions when corrosion might increase above acceptable levels.This paper presents an evaluation of telluric-associated corrosion derived from measured and modelled PSP variations. The corrosion rates (metal loss per year) due to varying telluric currents with continuous frequency spectra (1 Hz–10−5 Hz) are approximated with the use of published experimental results derived for the specific sets of fixed frequencies.Results are presented for PSP observed on Australian and European pipelines during two periods of strong geomagnetic activity (in 2003 and 2004) and for identical hypothetical pipelines located at different latitudes for the entire year 2004.From the analysis of recorded PSP, it was found that the corrosion rates for a near-equatorial pipeline (Australia) could be higher than for mid-latitudes (Europe). This is possible because telluric-associated corrosion rates depend not only on geomagnetic activity, but on the properties of the pipeline coating, the performance of the cathodic protection system and environmental conditions.The study demonstrated that without cathodic protection the estimated corrosion rates exceeded the benchmark values recommended by national and international standards, and in exceptional case can exceed the acceptable values even with cathodic protection.Telluric-associated corrosion estimated for the identical hypothetical pipelines located in zones with different geomagnetic activity, clearly demonstrated the latitudinal dependence. The substantial increase of corrosion rates (about 5 times) has been found with increase of latitude from subauroral to auroral locations.

Ring Current Morphology From MMS Observations

AbstractWe directly estimate the in situ current density of the Earth’s ring current (RC) using the curlometer method and investigate its morphology using the small spatial separations and high accuracy of the Magnetospheric Multiscale mission. Through statistical analysis of data from September 2015 to the end of 2016, covering the region of 2–8 RE (Earth radius, 6,371 km), we reveal an almost complete near‐equatorial (within ) RC morphology in terms of radial distance and magnetic local time (MLT) which complements and extends that found from previous studies. We found no evidence of RC enhancement on the dusk side during geomagnetic active periods, but details of MLT asymmetries in, and the boundary between, the inner (eastward) and outer (westward) currents are revealed. We propose that part of the asymmetry demonstrated here suggests that in addition to the overall persistence of the westward RC, two large banana‐like currents are directly observed, one which could arise from a peak of plasma pressure near ∼4.8 RE on the noon side and the other from a valley of plasma pressure which could arise near ∼4.8 RE on the night side.

Classification and Distribution of the Dayside Ion Upflows Associated with Auroral Particle Precipitation

Two important phenomena of the solar wind–magnetosphere–ionosphere coupling are auroral particle precipitation and the formation of ions flowing upward from the ionosphere. They have opposite transport directions of energy and substance. Based on the observations of particle precipitation and ion drift from the DMSP F13 satellite in January and July 2005, the ionospheric ion upflows in dayside auroral oval (0600–1800 MLT) can be divided into five types according to the velocity of ion upflows and the spectrum characteristics of auroral particle precipitation, and the distribution for different types of ion upflows is studied. The results show that the ion upflows mainly occur in the geomagnetic latitude (MLAT) range of 70–80°.The main magnetospheric source region of ion upflows (type A and D) caused by the accelerated electron (mainly the soft electron) corresponds to Low Latitude Boundary Layer (LLBL) and Cusp, and ion upflows of type B and C (related to the process of ambipolar diffusion caused by electron acceleration) mainly occur in LLBL and Boundary Plasma Sheet (BPS), while ion upflows of type E without electron acceleration mainly occur in the central plasma sheet (CPS).The dawn–dusk asymmetry is obvious in the winter season, with the ion upflows mainly occurring on the dawn/dusk side ionosphere. However, the ion upflows in summer mainly occur at the magnetic noon, with a symmetric distribution centered at the magnetic noon. The occurrence of ion upflow in winter is significantly higher than that in summer, and it is significantly enhanced during the period of moderate geomagnetic activity. The upward region expands to the lower latitude when the geomagnetic activity is enhanced. The effect of interplanetary magnetic field (IMF) components has also been studied in this paper. When IMF Bx is negative, the upflow occurrence increases in the region of 1500–1800 MLT and 0600–0900 MLT, with the MLAT range below 70°. The direction of IMF By may lead to the high-incidence area reverse at the prenoon or postnoon region. The occurrence of ion upflows with the MLAT range below 75° increases significantly when IMF is southward. Type A ion upflow has the highest velocity of ion upflows, followed by type E, and type D has the lowest. The average velocity of ion upflows in winter is significantly higher than that in summer.

The preliminary result of orbital atmosphere detector on board spherical satellite

<p indent="0mm">The spherical satellite is Chinese first spherical small satellite, integrating atmospheric composition, atmospheric density detection and precision orbit determination. The payload is the Orbital Atmosphere Detector, which was launched into near circular polar orbit with the orbit altitude of <sc>520 km</sc> and inclination angle of 97.4° on 14 October, 2021. The scientific objectives, operating principle and the ground calibration results of the Orbital Atmosphere Detector are presented in this paper. The preliminary <italic>in-situ</italic> observed results are analyzed and discussed. The observed mass densities are strongly correlated with <italic>F</italic>10.7 and <italic>Kp</italic>. The peak-to-valley ratio of observed mass densities during the quiet period of solar and geomagnetic activity on 3 November 2021 was 3.02; the peak of observed mass density increased from 2.8×10⁻¹³ to 8.0×<sc>10⁻¹³ kg/m³</sc> during the strong geomagnetic storm event on 4 November, 2021, an increase of 2.857 times compared to the MSIS00 model of 1.316 times. The observed data show that the increase in atmospheric density started at the South Pole and spread to the middle and low latitudes, while the MSIS00 model only show a weak symmetrically increase between the northern and southern hemispheres during the storm. The observed results show that the observed data objectively reflect the spatial and temporal distribution of thermosphere density during the quiet period and the geomagnetic storm event, and thermosphere atmospheric model correction can be implemented based on the large amount of observed data.

Performance Evaluation of Modified IRI2016 and Its Application to the 24 hr Ahead Forecast foF2 Mapping Over China

AbstractIn this paper, we have modified the International Reference Ionosphere model 2016 (IRI2016) with the Global Navigation Satellite System total electron content data observation in China by adjusting the ionospheric index (IG12) for given location and time. The capability of the modified IRI2016 to reproduce the F2 layer critical frequency foF2 is validated for high/low solar activity conditions and disturbed geomagnetic conditions for the time period 2014–2017 over low‐latitude ionosonde station located at Sanya in China. The analysis shows that the modified IRI2016 better reproduced the variability of the observed foF2 versus time and seasons. Also, the modified IRI2016 foF2 prediction exhibits lower root mean square error and higher correlation coefficients (R) over different solar activity periods, and significantly reduces the average percentage deviations (△foF2(%)) under enhanced geomagnetic activity periods. Subsequently, the 24 hr ahead forecast foF2 map over China constructed by the combination of the modified IRI2016 and the eXtreme Gradient Boosting algorithm is presented for the first time. The promising performance of the modified IRI2016 indicates that this combination method may be an effective way to predict the ionospheric parameters, though further validations are needed in the future work.

Occurrence of Ionospheric irregularities over Brazil and Africa during the 2019 Antarctic minor sudden stratospheric warming

The influence of sudden stratospheric warming (SSW) on the ionosphere and ionospheric irregularities has been studied extensively over the years. However, majority of these investigations have been conducted using warming events originating from the northern hemisphere. Only a few studies have been done on ionospheric variations due to the Antarctic SSW events and to the best of our knowledge, there have not been any studies on southern hemisphere SSW and the occurrence of ionospheric irregularities. In this study, the occurrence of ionospheric irregularities during the 2019 minor Southern hemisphere (SH)/Antarctic SSW is investigated. The event occurs in a relatively calm solar and geomagnetic activity period which makes it possible to identify the effects of SSW on the occurrence of irregularities. Three ionosondes located in different latitudinal regions in Brazil as well as a network of ground-based GPS receiver stations located in both Brazil and Africa were used for this undertaking. Complimentary data from the same ionosonde stations using the same months from 2017 and 2018 were also used. On average more Spread-F was observed in 2019 than in 2017 or 2018 at all stations. ROT observations showed more occurrence in the Brazil sectors followed by West Africa and thenEast Africa. It was observed that the occurrence frequency decreased between 8% and 46 % from the pre-SSW phase to ascending/peak phases and from 2018 to 2019 for the peak phase.

Analysis of Orbital Atmospheric Density from QQ-Satellite Precision Orbits Based on GNSS Observations

Atmospheric drag provides an indirect approach for evaluating atmospheric mass density, which can be derived from the Precise Orbit Determination (POD) of Low Earth Orbit (LEO) satellites. A method was developed to estimate nongravitational acceleration, which includes the drag acceleration of the thermospheric density model and empirical force acceleration in the velocity direction from the centimeter-level reduced-dynamic POD. The main research achievements include the study of atmospheric responses to geomagnetic storms, especially after the launch of the spherical Qiu Qiu (QQ)-Satellite (QQ-Satellite) with the global navigation system satellite (GNSS) receiver onboard tracking the Global Positioning System (GPS) and Beidou System (BDS) data. Using this derivation method, the high-accuracy POD atmospheric density was determined from these data, resulting in better agreement among the QQ-Satellite-derived densities and the NRLMSISE-00 model densities. In addition, the POD-derived density exhibited a more sensitive response to magnetic storms. Improved accuracy of short-term orbit predictions using derived density was one of the aims of this study. Preliminary experiments using densities derived from the QQ-Satellite showed promising and encouraging results in reducing orbit propagation errors within 24 h, especially during periods of geomagnetic activity.

A Climatology of Long-Duration High 2-MeV Electron Flux Periods in the Outer Radiation Belt.

Since the advent of the Space Age, the importance of understanding and forecasting relativistic electron fluxes in the Earth’s radiation belts has been steadily growing due to the threat that such particles pose to satellite electronics. Here, we provide a model of long‐duration periods of high time‐integrated 2‐MeV electron flux deep inside the outer radiation belt, based on the significant correlation obtained in 2001–2017 between time‐integrated electron flux measured by satellites and a measure of the preceding time‐integrated homogenized aa H geomagnetic index. We show that this correlation is likely due to a stronger cumulative chorus wave‐driven acceleration of relativistic electrons and a stronger cumulative inward radial diffusion of such electrons during periods of higher time‐integrated geomagnetic activity. Return levels of 2‐MeV electron flux are provided based on Extreme Value analysis of time‐integrated geomagnetic activity over 1868–2017, in rough agreement with estimates based on 20‐year data sets of measured flux. A high correlation is also found between our measure of time‐integrated geomagnetic activity averaged over each solar cycle and averaged sunspot numbers, potentially paving the way for forecasts of time‐integrated relativistic electron flux during future solar cycles based on predictions of solar activity.

Modeling and forecasting of ionosphere TEC using least squares SVM in central Europe

We propose a new method for spatio-temporal modeling of ionosphere total electron content (TEC) using least squares support vector machine (LS-SVM). In the SVM model, dual programming is used to solve the system of equations. Therefore, large-scale problem solving with the SVM greatly increases computation time and decreases accuracy. To overcome these limitations, a LS-SVM method is proposed. This method uses simple linear equations to solve the system of equations. As a result, the complexity of the computational algorithm is reduced. In addition, the convergence speed and accuracy of the results increase. To evaluate the new method, observations of 30 GNSS stations in the central Europe are used. The observations are for 80 days from 2014, with different solar (F10.7) and geomagnetic activity (KP and DST) indices. The results of the LS-SVM model at three control stations are compared with the vertical TEC (VTEC) of the GPS and also with the VTEC of the SVM, NeQuick and global ionosphere map (GIM) models. On all days considered, the averaged RMSE of the LS-SVM, SVM, GIM and NeQuick models at the control stations are calculated as 2.45, 3.13, 4.61 and 7.48 TECU, respectively. In precise point positioning (PPP) analysis and at the high geomagnetic activity, the maximum RMSE of LS-SVM, SVM, GIM and NeQuick models are computed 52.34, 63.22, 70.21 and 79.55 mm, respectively. During periods of low geomagnetic activity, the RMSE of the LS-SVM model is lower than the other models. Seasonal error analysis of all 4 models shows that the LS-SVM model has less error in different seasons compared to the other models. The results also show that the proposed model has a higher speed and accuracy than the SVM, GIM and NeQuick. Therefore, it can be considered a regional model of the ionosphere in the European region.

Solar and geomagnetic activity reduces pulmonary function and enhances particulate pollution effects

BackgroundIncreased solar and geomagnetic activity (SGA) may alter sympathetic nervous system activity, reduce antioxidant activity, and modulate physiochemical processes that contribute to atmospheric aerosols, all which may reduce pulmonary function. ObjectivesInvestigate associations between forced expiratory volume at 1 s (FEV1) and forced vital capacity (FVC) with SGA, and assess whether SGA enhances adverse effects of particulate pollution, black carbon (BC) and particulate matter ≤2.5 μm in diameter (PM2.5). Methods: We conducted a repeated measures analysis in 726 Normative Aging Study participants (Boston, Massachusetts, USA) between 2000 and 2017, using interplanetary magnetic field (IMF), planetary K index (Kp), and sunspot number (SSN) as SGA measures. Linear mixed effects models were used to assess exposure moving averages up to 28 days for both SGA and pollution. ResultsIncreases in IMF, Kp Index and SSN from the day of the pulmonary function test averaged through day 28 of were associated with a significant decrement in FEV1 and FVC, after adjusting for potential confounders. There were greater effects for longer moving averages and enhanced effects of PM2.5 and BC on FEV1 and FVC with increased SGA. For example, for each inter-quartile increase (4.55 μg/m3) in average PM2.5 28 days before testing, low IMF (10th percentile: 3.2 nT) was associated with a −21.4 ml (95 % CI: −60.8, 18.1) and −7.1 ml (95 % CI: −37.7, 23·4) decrease in FVC and FEV1, respectively; high IMF (90th percentile: 9.0 nT) was associated with a −120.7 ml (95 % CI:-166.5, −74.9) and −78.6 ml (95 % CI: −114.3, −42·8) decrease in FVC and FEV1, respectively. DiscussionIncreased periods of solar and geomagnetic activity may directly contribute to impaired pulmonary function and also enhance effects of PM2.5 and BC. Since exposure to solar activity is ubiquitous, stricter measures in reducing air pollution exposures are warranted, particularly in elderly populations.

Influence of the solar wind high-speed streams on the thermospheric neutral density during the declining phase of solar cycle 23

Thermospheric neutral density derived from the GRACE A satellite and normalized at altitude of 490 km (ρ) are used to investigate the ρ behavior during the period of recurrent geomagnetic activity (25 January - 5 May, 2005) caused by solar wind high-speed streams (HSSs). The north and south hemispheric ρ values divided in three latitudinal bins are analyzed separately at dayside and nightside. The variations, not caused by solar/geomagnetic activity, are investigated accounting for the relationship between solar flux index, illumination, latitude and DOY for particular magnetic local times (MLTs). Analysis has shown that: ρ increases/decreases from high to low latitudes at dayside/nightside; ρ increases from high to low latitudes at dayside caused by solar EUV radiation is most prominent around MLT = 14 and decrease rapidly with departure from this MLT; the difference between north and south hemispheric ρ values are not the same prior and after the equinox; quiet time ρ differs among latitudinal bins; ρ contains a clear imprint of solar/geomagnetic activity. The cross-correlation analysis reveals a high degree of correlation between ρ and different employed ρ indicators. Time lags based on all ρ indicators suggest that ρ disturbance: occurs about 4 h earlier at high than at lower latitudes and propagates presumably without losses toward equatorial region both at dayside and nightside; propagates faster between polar and mid latitudes at dayside and between mid and low latitudes at nightside. This study provides the most probable characteristics of the ρ variations during the periods in which magnetospheric-thermospheric system is affected primarily by HSSs.

On the F3 layer occurrence and drift over the equatorial location of Thiruvananthapuram

A study has been carried out on various aspects of occurrence as well as vertical drift of F3 layer over the magnetic equatorial location of Thiruvananthapuram [8.5 0N; 77 0E; dip lat of 0.5 0N] in India for the period from 1990−2009 using ionosonde observations. Diurnally, F3 layer occurrence exhibits a double peak pattern with maximum occurrence in the pre-noon, followed by a broad peak in the post-noon hours. The F3 layer exhibits a seasonal pattern of occurrence which is prominent only during low solar activity periods. The solar cycle variability of F3 layer occurrence is brought out in the present study using data from solar cycle 22 and 23. Further it is clear from the present analysis that F3 layer occurrence is high during periods of lower geomagnetic activity with Ap less than 20. The present study brings out an important aspect that there is no significant difference in the occurrence percentage of pre-noon F3 layers during solar cycle 22 and 23, while the post-noon F3 layer occurrence increases during the deep solar minimum periods at the end of solar cycle 23. The role of Counter Electrojet and the ensuing thermosphere-ionosphere coupling processes are proposed to be the reason for the above stated features of occurrence. The seasonal as well as solar activity dependence of the vertical drift of F3 layers is also brought out. The influence of thermospheric winds in determining the drift velocity is revealed.

Effects of Electron Precipitation on E‐Region Instabilities: Theoretical Analysis

AbstractDuring periods of strong geomagnetic activity, intense currents and electric fields originating in the magnetosphere inundate the high‐latitude E‐region ionosphere. These strong electric fields drive plasma instabilities, including the Farley‐Buneman instability (FBI). These instabilities give rise to small‐scale plasma turbulence that modifies the large‐scale ionospheric conductance that, in turn, affects the evolution of the magnetosphere‐ionosphere‐thermosphere system. Also, during geomagnetic storms, high‐energy precipitating electrons, ≳5 keV, frequently penetrate down to the same regions where the intense currents and electric fields exist. This research examines the effects of precipitating electrons on the generation of the FBI and shows that, under many common conditions, it can easily suppress the FBI in a predictable manner. We demonstrate that the plasma pressure of superthermal electrons may significantly exceed the regular plasma pressure of the cold ionospheric plasma. This effect will increase the FBI threshold and suppress the instability in auroral regions. However, our detailed theoretical analysis shows that the effect of the superthermal precipitating electrons on the FBI threshold is much stronger than the pressure effect. The energy dependence of the electron‐N2 collision frequency can greatly enhance the effect of this additional pressure, further suppressing the FBI, even at a moderate precipitation level. Therefore, we expect that precipitation will exert an additional significant feedback on the magnetosphere by preventing the elevated conductivity caused by FBI driven turbulence. Both the turbulence‐enhanced conductivities and this suppression should be taken into account in global modeling of the magnetosphere‐ionosphere coupling.

Evaluating Auroral Forecasts Against Satellite Observations

AbstractThe aurora is a readily visible phenomenon of interest to many members of the public. However, the aurora and associated phenomena can also significantly impact communications, ground‐based infrastructure, and high‐altitude radiation exposure. Forecasting the location of the auroral oval is therefore a key component of space weather forecast operations. A version of the OVATION‐Prime 2013 auroral precipitation model (Newell et al., 2014, https://doi.org/10.1002/2014sw001056) was used by the UK Met Office Space Weather Operations Centre (MOSWOC). The operational implementation of the OVATION‐Prime 2013 model at the UK Met Office delivered a 30‐min forecast of the location of the auroral oval and the probability of observing the aurora. Using weather forecast evaluation techniques, we evaluate the ability of the OVATION‐Prime 2013 model forecasts to predict the location and probability of the aurora occurring by comparing the forecasts with auroral boundaries determined from data from the IMAGE satellite between 2000 and 2002. Our analysis shows that the operational model performs well at predicting the location of the auroral oval, with a relative operating characteristic (ROC) score of 0.82. The model performance is reduced in the dayside local time sectors (ROC score = 0.59) and during periods of higher geomagnetic activity (ROC score of 0.55 for Kp = 8). As a probabilistic forecast, OVATION‐Prime 2013 tends to underpredict the occurrence of aurora by a factor of 1.1–6, while probabilities of over 90% are overpredicted.

Realistic Dispersion of Plasmaspheric Hiss in the Inner Magnetosphere and Its Effect on Wave-induced Electron Scattering Rates

Abstract The cold plasma approximation is a common treatment to study wave–particle interactions between plasmaspheric hiss and magnetospheric electrons, which, however, can become a challenge during periods of disturbed geomagnetic activity. To assess the validity of the cold plasma dispersion relation of plasmaspheric hiss, we adopt the cold plasma theory to calculate the wave magnetic field intensities from the electric field intensities observed by Van Allen Probe A from 2012 October 1 to 2018 February 28. Comparisons between the observed and converted hiss magnetic field intensities capture pronounced differences with the enhancement of substorm activity, and exhibit the largest discrepancies on the nightside MLT sector for low-frequency hiss waves. We also use both the hiss dispersion curves derived from the observations and the cold plasma dispersion relation to evaluate hiss-induced electron diffusion coefficients under different substorm activity conditions. The results indicate that the profiles of electron diffusion rates vary considerably for the two hiss dispersion relations and that the differences between them become increasingly distinct with substorm activity intensification. Our study therefore demonstrates that the cold plasma theory can become less reliable for plasmaspheric hiss waves under disturbed geomagnetic circumstances and that the realistic wave dispersion is essential to better quantify the electron scattering effect of hiss waves, which needs to be carefully incorporated into future global simulations of the generation and propagation of plasmaspheric hiss and associated dynamic variability of radiation belt electrons.

A Combined Neural Network‐ and Physics‐Based Approach for Modeling Plasmasphere Dynamics

AbstractIn recent years, feedforward neural networks (NNs) have been successfully applied to reconstruct global plasmasphere dynamics in the equatorial plane. These neural network‐based models capture the large‐scale dynamics of the plasmasphere, such as plume formation and erosion of the plasmasphere on the nightside. However, their performance depends strongly on the availability of training data. When the data coverage is limited or non‐existent, as occurs during geomagnetic storms, the performance of NNs significantly decreases, as networks inherently cannot learn from the limited number of examples. This limitation can be overcome by employing physics‐based modeling during strong geomagnetic storms. Physics‐based models show a stable performance during periods of disturbed geomagnetic activity if they are correctly initialized and configured. In this study, we illustrate how to combine the neural network‐ and physics‐based models of the plasmasphere in an optimal way by using data assimilation. The proposed approach utilizes advantages of both neural network‐ and physics‐based modeling and produces global plasma density reconstructions for both quiet and disturbed geomagnetic activity, including extreme geomagnetic storms. We validate the models quantitatively by comparing their output to the in‐situ density measurements from RBSP‐A for an 18‐month out‐of‐sample period from June 30, 2016 to January 01, 2018 and computing performance metrics. To validate the global density reconstructions qualitatively, we compare them to the IMAGE EUV images of the He+ particle distribution in the Earth's plasmasphere for a number of events in the past, including the Halloween storm in 2003.

Землетрясения и геомагнитные возмущения

The article addresses the problem of the connection of earthquakes with geomagnetic phenomena. We have carried out an experimental study using a method based, firstly, on the separation of periods of geomagnetic activity into extremely quiet and disturbed, and, secondly, on the description of seismic activity with an index called the global daily magnitude (GDM). By analyzing the NEIC earthquake catalog of the US Geological Survey over a 20-year period from 1980 to 1999, we have shown that the planetary activity of earthquakes under extremely quiet geomagnetic conditions is noticeably higher than under disturbed conditions. The detected tendency for seismic activity to increase in extremely quiet periods of geomagnetic activity has indirectly been confirmed by the analysis of 35 earthquakes with magnitude 8 and higher, which occurred on Earth from 1980 to 2019. We have found that in extremely quiet geomagnetic conditions, the probability of the occurrence of strong earthquakes is noticeably higher. The result qualitatively confirms the assumption of a change in the regime of seismic activity due to the influence of alternating magnetic fields on the ductility of rocks.

EARTHQUAKES AND GEOMAGNETIC DISTURBANCES

The article addresses the problem of the connection of earthquakes with geomagnetic phenomena. We have carried out an experimental study using a method based, firstly, on the separation of periods of geomagnetic activity into extremely quiet and disturbed, and, secondly, on the description of seismic activity with an index called the global daily magnitude (GDM). By analyzing the NEIC earthquake catalog of the US Geological Survey over a 20-year period from 1980 to 1999, we have shown that the planetary activity of earthquakes under extremely quiet geomagnetic conditions is noticeably higher than under disturbed conditions. The detected tendency for seismic activity to increase in extremely quiet periods of geomagnetic activity has indirectly been confirmed by the analysis of 35 earthquakes with magnitude 8 and higher, which occurred on Earth from 1980 to 2019. We have found that in extremely quiet geomagnetic conditions, the probability of the occurrence of strong earthquakes is noticeably higher. The result qualitatively confirms the assumption of a change in the regime of seismic activity due to the influence of alternating magnetic fields on the ductility of rocks.