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The injection of energy into the Earth's magnetosphere during geomagnetic storms and substorms has a direct impact on the ionosphere in the auroral and sub-auroral regions. This influence can be observed through phenomena such as the expansion of the auroral oval, and fluctuations in plasma density and the intensity of the field-aligned current (FAC) system. Changes in the geomagnetic environment significantly affect the main ionospheric trough (MIT) and field-aligned currents (FACs). In this study, we analysed two geomagnetic storms of different origins—October 2015 and September 2017 that occurred during solar cycle 24. Both storms were characterised by two minima of the Dst index and classified as two-step storms. In this work, we investigate the evolution of FACs density, the displacement of MIT and FACs during the development of geomagnetic storms, and we quest for the relationship between field-aligned currents and the main ionospheric trough. We noticed a connection between the positions of the main ionospheric trough minima and the Dst index, found cases especially during the main and recovery phase of the storms when FACs increase after leaving the ionospheric trough, and observed the predominance of downward currents in the area of the MIT which suggest their influence on the formation of this region of depleted plasma density. [ABSTRACT FROM AUTHOR]

A novel tool utilizing machine learning techniques was designed to forecast ap index values for the next three consecutive days (24 values). The tool employs time series data from the 3 h ap index of solar cycles 23 and 24 to train the Long Short-Term Memory (LSTM) model, predicting ap index values for the next 72 h at three-hour intervals. During periods of quiet geomagnetic activity, the LSTM model's performance is sufficient to yield favorable outcomes. Nevertheless, during geomagnetically disturbed conditions, such as geomagnetic storms of different levels, the model needs to be adapted in order to provide accurate ap index results. In particular, when coronal mass ejections occur, the ap Prediction tool is modulated by inserting predominant features of coronal mass ejections such as the date of the event, the estimated time of arrival and the linear speed. In the present work, this tool is described thoroughly; moreover, results for G2 and G3 geomagnetic storms are presented. [ABSTRACT FROM AUTHOR]

On 4 November 2021, during the rising phase of solar cycle 25, an intense geomagnetic storm (Kp = 8−) occurred. The effects of this storm on the outer magnetospheric region up to the ionospheric heights have already been examined in previous investigations. This work is focused on the analysis of the solar wind conditions before and during the geomagnetic storm, the high-latitude electrodynamics conditions, estimated through empirical models, and the response of the atmosphere in both hemispheres, based on parameters from the ECMWF ERA5 atmospheric reanalysis dataset. Our investigations are also supported by counter-test analysis and Monte Carlo tests. We find, for both hemispheres, a significant correspondence, within 1–2 days, between high-latitude electrodynamics variations and changes in the temperature, specific humidity, and meridional and zonal winds, in both the troposphere and stratosphere. The results indicate that, in the complex solar wind–atmosphere relationship, a significant role might be played by the intensification of the polar cap potential. We also study the reciprocal relation between the ionospheric Joule heating, calculated from a model, and two adiabatic invariants used in the analysis of solar wind turbulence. [ABSTRACT FROM AUTHOR]

Based on two meteor radars in mid‐latitudes of China, the mid‐latitude lower thermospheric neutral wind responses to the 2015 St. Patrick's Day great storm are investigated. The AE and PCN indices presented the similar quasi‐5‐hour oscillations during the storm. Interestingly, the analogous and close‐correlated storm‐time quasi‐5‐hour oscillations were also observed in both the meridional wind differences at 90–102 km derived from meteor radars. The meridional wind disturbances in the lower thermosphere also showed the extension toward the lower latitudes. It has been found that the enhanced equatorward wind disturbances at 250 km estimated by the Horizontal Wind Model‐14 and Fabry‐Perot Interferometer (FPI) emerged accordingly with the increases of AE and PCN with a time delay. And the enhancements of equatorward (poleward) wind disturbances at 250 km were accompanied by the increments of equatorward (poleward) wind disturbances at 94 km with a time lag of a few hours. It is thus suggested that the multiple intensified Joule heating events with quasi‐5‐hour time intervals were triggered by the successive substorm expansions during the storm. Then the Joule heating events led to the vertical wind and temperature disturbances in the mid‐latitude lower thermosphere via disturbing the thermospheric meridional circulation, which consequently induced the quasi‐5‐hour meridional wind disturbances therein. Plain Language Summary: The neutral temperature and global circulation in the middle and upper atmosphere can be strongly disturbed by the solar and geomagnetic activity. However, the effects of geomagnetic activity on the neutral winds in the mesosphere and lower thermosphere region at middle latitudes have not been fully understood. Using the neutral wind measurements from two meteor radars located at latitudes of 53.5°N and 40.3°N around 120°E meridian in China, we found that the meridional winds at different latitudes showed the prominent and similar disturbance patterns during the 2015 St. Patrick's Day geomagnetic storm. There exhibited the obvious quasi‐5‐hour oscillations in the meridional wind differences at 90–102 km derived from meteor radars. And such wind oscillations appeared to be analogous and close‐correlated to the quasi‐5‐hour oscillations in the AE and PCN indices. The possible contributors and physical processes responsible for such wind disturbances in the mid‐latitude lower thermosphere are discussed. This study is helpful to understand the influences of geomagnetic activity on the neutral winds in the mid‐latitude lower thermosphere region as well as the possible dynamic processes therein. Key Points: Storm‐time quasi‐5‐hour oscillations emerged in both the AE/PCN indices and the meridional winds in the mid‐latitude lower thermosphereThe increments of equatorward/poleward winds at 94 km exhibited the close correspondence and correlation to those at 250 km with a time lagThe successive Joule heating events led to the periodic meridional wind disturbances via disturbing thermospheric meridional circulation [ABSTRACT FROM AUTHOR]

The updated database of Forbush effects and interplanetary disturbances (https://tools.izmiran.ru/feid) is used for an extensive analysis of various characteristics of events caused by the influence of interacting solar wind disturbances on the near-Earth space. In particular, the cases of different combinations of the pair interaction of high-speed streams from coronal holes and coronal mass ejections over the long period from 1995 to 2022 are considered. Variations in the flux of galactic cosmic rays (with a rigidity of 10 GV) and changes in the parameters of the interplanetary medium and geomagnetic activity are described. It is shown that the degree of mutual influence depends on the time between the detection of neighboring events; with the most pronounced changes in various parameters for events whose interaction occurred before reaching Earth's orbit. It is also established that in interacting solar wind disturbances not only the extremes of the parameters of cosmic rays, interplanetary medium, and geomagnetic activity but also their time profiles are subject to changes. [ABSTRACT FROM AUTHOR]

Space weather forecasts are of utmost importance in safeguarding navigation, communication, and electric power system operations, satellites from orbital drag, and the astronauts in the International Space Station from hazardous space radiation during extreme space weather conditions. The finest space weather prediction requires a clear understanding of solar wind‐magnetosphere coupling. The in‐situ measurements of the solar wind properties give unique information about the Sun and its activity on smaller to longer timescales. The present work investigates the influence of solar activity on the coupling of solar wind and Earth's magnetosphere during 23–24 solar cycles. The geomagnetic storms with Symmetric H‐component (SYMH) ≤ −85 nT during the 23–24 solar cycles are considered. We present the results of statistical analysis and relationships between the various solar wind parameters such as the total strength of interplanetary magnetic field (B) and its three‐axis components (Bx, By, and Bz), solar wind proton density (Nsw), solar wind speed (Vsw), SYMH indices, the amplitude, duration, and profile of the geomagnetic storms. The integrated electric field and integrated SYMH index during storms show the highest correlation of 0.92, implying that integrated SYMH is a better proxy of the injected solar wind energy in the magnetosphere in the form of the ring current. Moreover, we do see the difference in the solar wind‐magnetosphere coupling efficiency during the phases of 23–24 solar cycles which is intriguing. Key Points: First observation: The Integrated Ey of solar wind and Integrated Symmetric H‐component show a strikingly high correlationSolar Wind (SW)‐Magnetosphere (M) coupling shows higher average efficiency during the 24th solar cycle compared to the 23rdLow solar activity (or solar minimum) shows elevated efficiency of SW‐M coupling [ABSTRACT FROM AUTHOR]

The dynamics of the intensity of cosmic rays is known to be different on the ascending and descending branches of the 11-year solar cycle, i.e., hysteresis phenomena are observed. Recently, it has been obtained that at shorter intervals on the scale of magnetic storms there are also signs of hysteresis in dependences of cosmic ray cutoff rigidities R (geomagnetic thresholds) on heliosphere and geosphere parameters. R is the rigidity below which a particle flux is cut off due to geomagnetic shielding. In this paper, we have analyzed the dependence of the geomagnetic storm index Dst and the variation of the ΔR thresholds on interplanetary magnetic field (IMF) and solar wind (SW) parameters during the two-step magnetic storm on September 7–8, 2017. We have found hysteresis phenomena in the following paired series: (1) dependences of Dst on SW and IMF parameters, and (2) dependences of ΔR on SW and IMF parameters. We have established that the dependence curves in the storm descending phase (main phase) and ascending phase (recovery phase) do not coincide — hysteresis loops are formed. A specific feature of the storm under study is the second lowering of Dst in the recovery phase. The hysteresis pattern reflects this specific storm dynamics, forming two hysteresis loops in response to the two Dst drops.

Using annual average values, the relationships are examined of the geomagnetic indices SYM-H, ASY-H, and Dst with solar wind parameters in 1981–2015. The data used was divided into two samples according to the sign of the north-south component Bn of the interplanetary magnetic field (IMF). Variations in the annual average values of each of the Dst, SYM-H, and ASY-H indices for southward and northward IMF have been found to be similar and their linear correlation coefficients r to be high: 0.871, 0.863, and 0.943 respectively. The similarity between variations of the indices with different signs of Bn is probably due to their connection with the number of sunspots. It has been established that Dst, SYM-H, and ASY-H depend on the solar wind parameter β: their absolute values decrease with increasing β, regardless of Bn sign. The decrease in the indices with increasing β is likely to be caused by the transition of the magnetosphere to a quiet state due to the increasing predominance of thermal pressure over magnetic one in the solar wind and a decrease in the level of solar wind turbulence. SYM-H and ASY-H have been found to reveal the closest relationships with β, whereas SYM-H more strongly depends on β for southward IMF (r=0.744) than for northward IMF (r=0.677). On the contrary, for ASY-H r=–0.741 at northward IMF and r=–0.719 at southward IMF. Similar to SYM-H, Dst (to a lesser extent) significantly correlates with β at southward IMF (r=0.629) and weaker at northward IMF (r=0.456).

The impact of interplanetary (IP) shocks on the Earth's magnetosphere can greatly disturb the geomagnetic field and electric currents in the magnetosphere-ionosphere system. At high latitudes, the current systems most affected by the shocks are the auroral electrojet currents. These currents then generate ground geomagnetically induced currents that couple with and are highly detrimental to ground artificial conductors including power transmission lines, oil/gas pipelines, railways, and submarine cables. Recent research has shown that the shock impact angle, the angle the shock normal vector performs with the Sun-Earth line, plays a major role in controlling the subsequent geomagnetic activity. More specifically, due to more symmetric magnetospheric compressions, nearly frontal shocks are usually more geoeffective than highly inclined shocks. In this study, we utilize a subset (332 events) of a shock list with more than 600 events to investigate, for the first time, shock impact angle effects on the subsequent GICs right after shock impact (compression effects) and several minutes after shock impact (substorm-like effects). We use GIC recordings from the Finnish natural gas pipeline performed near the Mäntsälä compression station in southern Finland. We find that GIC peaks ( > 5 A) occurring after shock impacts are mostly caused by nearly frontal shocks and occur in the post-noon/dusk magnetic local time sector. These GIC peaks are presumably triggered by partial ring current intensifications in the dusk sector. On the other hand, more intense GIC peaks ( > 20 A) generally occur several minutes after shock impacts and are located around the magnetic midnight terminator. These GIC peaks are most likely caused by intense energetic particle injections from the magnetotail which frequently occur during substorms. The results of this work are relevant to studies aiming at predicting GICs following solar wind driving under different levels of asymmetric solar wind forcing. [ABSTRACT FROM AUTHOR]

The magnetosphere‐ionosphere‐thermosphere system is externally driven by the energy input from the solar wind. A part of the solar wind energy deposited in the magnetosphere during geomagnetically active periods dissipates into the thermosphere. Previous studies have reported temperature perturbations in the lower thermosphere during geomagnetic storms. The present study aims to assess the climatological spatial pattern of the lower thermospheric response to geomagnetic activity at high latitudes based on 21 years of temperature measurements by the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument onboard the TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite and their comparison with the recently developed half‐hourly geomagnetic activity index Hp30. The temperature response to geomagnetic activity, evaluated at different seasons and altitudes, is better organized in magnetic coordinates than in geographic coordinates. At 110 km, the temperature increases with Hp30 at all magnetic local times, but with a prominent dusk‐dawn asymmetry in the magnitude. That is, the temperature variation per unit Hp30 is larger in the dusk sector than in the dawn sector. At 106 km, the response in the dawn sector is further reduced or even negative. These results provide observational evidence to support earlier theoretical predictions; according to which, both storm‐induced vertical wind and Joule heating contribute to the temperature increase in the dusk sector, while in the dawn sector, the vertical wind acts to cool the air and thus counteracts Joule heating. Key Points: High‐latitude lower thermospheric temperature response to geomagnetic activity depends on magnetic local time and magnetic latitudeAbove 100 km, strong and weak (or even negative) responses occur in the dusk and dawn sectors, respectivelyThe results agree with earlier theoretical predictions, highlighting the importance of storm‐induced vertical wind and Joule heating [ABSTRACT FROM AUTHOR]

The effects of solar activity and the accompanying space weather events on human pathological conditions, physiological parameters and other psycho-physiological disturbances have been analyzed in numerous recent investigations. Moreover, many of these studies have particularly focused on the different physical reactions humans have, according to their sex, during variations in the physical environment. In the framework of the above, this work analyses heart rate data obtained from volunteers (687 men and 534 women) from three different regions (Athens, Piraeus and Heraklion) of Greece in relation to the geophysical activity and variations of environmental factors. Dst index and Ap index data, along with cosmic ray intensity data derived from the Athens Neutron Monitor Station (A.Ne.Mo.S.), were used. The study expands from April 2011 to January 2018, covering solar cycle 24. The ANalysis Of Variance (ANOVA) and the superimposed epochs methods were used in order to examine heart rate variations depending on sex. Results revealed that women tend to be more sensitive to physical environmental changes. Statistically significant results are related to the geomagnetic activity but were not obtained for cosmic ray variations. [ABSTRACT FROM AUTHOR]

The cyclic properties of solar-geomagnetic activity and global surface temperature have been investigated using trend, frequency and time-frequency analyses. Results reveal that on decadal-to-centennial timescales, low-frequency cycles in the half-century (~49 to 56 years per cycle) and Gleisberg (~99 to 114 years per cycle) range run in the background of the Schwabe (~9 to 11 years per cycle) as the dominant cycle of solargeomagnetic activity. The only dominant cycle in the global surface temperature series is the half-century cycle and suggests a possible causal link between it and solar-geomagnetic activity phenomena. Evolution of the amplitudes of the cycles is such that the Schwabe and Gleisberg periods have increased in power from the beginning of the series until the mid-20th century after which they declined. The half-century cycle decreased in amplitude after 1800 to the present. For geomagnetic activity, the amplitude of Gleisberg cycle increased from the beginning of the series around 2000 while the amplitudes of Schwabe and half-century cycles declined within the same interval, except the Schwabe cycle which amplitude increased rapidly after 1980 to the present. For the global surface temperature, the amplitudes of Gleisberg and half-century cycles have continuously increased from the beginning of the series while Schwabe cycle oscillates with very low amplitudes until 1980 after which it increased slightly. Evolution of the amplitudes of cycles of solar-gemagnetic activity suggests a recovery from Maunder Minimum and decline into a grand epsode most likely to be a minimum. [ABSTRACT FROM AUTHOR]

The results of the analysis of time series for 5 years of observations of geophysical (ecological) rhythms, atmospheric pressure, and geomagnetic activity, were considered and their effect on human blood pressure and heart rate for time periods of fluctuations more than daily was assessed. It was found that during periods of about 15 days, when atmospheric pressure changed smoothly and slightly, a calmer heart rate and fluctuations in blood pressure were observed. Such "calm" periods of time were observed mainly in the summer months from July to August, usually only once per season. A comparison of the graphs of fluctuations in systolic pressure and the geomagnetic activity index showed a correlation between them three times higher than the correlation between systolic pressure and atmospheric pressure. This means that a geomagnetic field with an activity index of more than 2 had a greater effect on increasing systolic pressure in humans. The analysis also showed that the periods of peaks in the atmospheric pressure spectra were in good agreement with the periods of heart rate rhythms. The result indicates that these rhythms in humans might be affected by synoptic processes passing through the region in the atmosphere such as cyclones and anticyclones; ultimately, the well-being of elderly and sick people might depend on them. This study, as well as taking the variability of geophysical parameters published by hydrometeorological services into account, makes it possible to predict the state of human health. [ABSTRACT FROM AUTHOR]

The impact of interplanetary (IP) shocks on the Earth’s magnetosphere can greatly disturb the geomagnetic field and electric currents in the magnetosphere-ionosphere system. At high latitudes, the current systems most affected by the shocks are the auroral electrojet currents. These currents then generate ground geomagnetically induced currents that couple with and are highly detrimental to ground artificial conductors including power transmission lines, oil/gas pipelines, railways, and submarine cables. Recent research has shown that the shock impact angle, the angle the shock normal vector performs with the Sun-Earth line, plays a major role in controlling the subsequent geomagnetic activity. More specifically, due to more symmetric magnetospheric compressions, nearly frontal shocks are usually more geoeffective than highly inclined shocks. In this study, we utilize a subset (332 events) of a shock list with more than 600 events to investigate, for the first time, shock impact angle effects on the subsequent GICs right after shock impact (compression effects) and several minutes after shock impact (substorm-like effects). We use GIC recordings from the Finnish natural gas pipeline performed near the Mäntsälä compression station in southern Finland. We find that GIC peaks (> 5 A) occurring after shock impacts are mostly caused by nearly frontal shocks and occur in the post-noon/dusk magnetic local time sector. These GIC peaks are presumably triggered by partial ring current intensifications in the dusk sector. On the other hand, more intense GIC peaks (> 20 A) generally occur several minutes after shock impacts and are located around the magnetic midnight terminator. These GIC peaks are most likely caused by intense energetic particle injections from the magnetotail which frequently occur during substorms. The results of this work are relevant to studies aiming at predicting GICs following solar wind driving under different levels of asymmetric solar wind forcing.

Aim. To study the seasonal dynamics of cardiovascular events (CVE) in the Russian Federation (RF) using medical and statistical data for the period 2016-2019, and also to establish an association of CVE risk with meteorological conditions.Material and methods. We used data on hospitalizations for 2016-2019 for hemorrhagic stroke (HS), ischemic stroke (IS), myocardial infarction (MI), and acute coronary syndrome (ACS).Results. Data analysis showed that the maximum number of HSs occurred in winter and spring, and the minimum in summer. The maximum number of ISs was recorded in spring and summer, while the minimum in winter and autumn. ACS occurred more often in winter and spring, MI — more often in spring. ACS was accompanied by MI in 44% of cases. In winter, the probability of HS increased with decreasing latitude.In summer, the risk of HS and IS was greater at lower air temperatures. In summer, the probability of IS and MI was associated with lower values of atmospheric pressure and partial density of oxygen (ρO2). In winter, the risk of IS increased at highr atmospheric pressure values. No convincing evidence was obtained of the influence of geomagnetic activity on the seasonal dynamics of the CVEs either throughout the Russian Federation or in the circumpolar regions.Conclusion. As a result, meteorological conditions influence the seasonal risk of CVEs. A decrease in ρO2 in summer significantly increases the CVE risk associated with ischemia, which should be taken into account when preventing CVEs.

Background: Studies show that changes in solar and geomagnetic activity (SGA) influence melatonin secretion and the autonomic nervous system. We evaluated associations between solar and geomagnetic activity and cognitive function in the Normative Aging Study from 1992 to 2013. Methods: We used logistic and linear generalized estimating equations and regressions to evaluate the associations between moving averages of sunspot number (SSN) and Kp index (a measure of geomagnetic activity) and a binary measure for Mini-Mental State Examination (MMSE) scores (≤25 or > 25) and six other cognitive tests as continuous measures, combined into one global composite score and considered separately. Results: A one-IQR increase in same-day SSN and Kp index were associated with 17% (95% CI: 3%, 34%) and 19% (95% CI: 4%, 36%) increases in the odds of low MMSE score. We observed small increases in the global cognitive score with increasing SSN, although we observed decreases specifically in relation to the backwards digit span test. Conclusions: Periods of high SGA were associated with cognitive function. SGA may not equally impact all aspects of cognitive function, as evidenced by differences in associations observed for the MMSE, global cognitive score, and individual cognitive tests. Given that much of the pathology of cognitive decline in the elderly remains unexplained, studies specifically targeting decline and with longer follow-up periods are warranted.

A novel tool utilizing machine learning techniques was designed to forecast ap index values for the next three consecutive days (24 values). The tool employs time series data from the 3 h ap index of solar cycles 23 and 24 to train the Long Short-Term Memory (LSTM) model, predicting ap index values for the next 72 h at three-hour intervals. During periods of quiet geomagnetic activity, the LSTM model’s performance is sufficient to yield favorable outcomes. Nevertheless, during geomagnetically disturbed conditions, such as geomagnetic storms of different levels, the model needs to be adapted in order to provide accurate ap index results. In particular, when coronal mass ejections occur, the ap Prediction tool is modulated by inserting predominant features of coronal mass ejections such as the date of the event, the estimated time of arrival and the linear speed. In the present work, this tool is described thoroughly; moreover, results for G2 and G3 geomagnetic storms are presented.

On 4 November 2021, during the rising phase of solar cycle 25, an intense geomagnetic storm (Kp = 8−) occurred. The effects of this storm on the outer magnetospheric region up to the ionospheric heights have already been examined in previous investigations. This work is focused on the analysis of the solar wind conditions before and during the geomagnetic storm, the high-latitude electrodynamics conditions, estimated through empirical models, and the response of the atmosphere in both hemispheres, based on parameters from the ECMWF ERA5 atmospheric reanalysis dataset. Our investigations are also supported by counter-test analysis and Monte Carlo tests. We find, for both hemispheres, a significant correspondence, within 1–2 days, between high-latitude electrodynamics variations and changes in the temperature, specific humidity, and meridional and zonal winds, in both the troposphere and stratosphere. The results indicate that, in the complex solar wind–atmosphere relationship, a significant role might be played by the intensification of the polar cap potential. We also study the reciprocal relation between the ionospheric Joule heating, calculated from a model, and two adiabatic invariants used in the analysis of solar wind turbulence.

The effects of solar activity and the accompanying space weather events on human pathological conditions, physiological parameters and other psycho-physiological disturbances have been analyzed in numerous recent investigations. Moreover, many of these studies have particularly focused on the different physical reactions humans have, according to their sex, during variations in the physical environment. In the framework of the above, this work analyses heart rate data obtained from volunteers (687 men and 534 women) from three different regions (Athens, Piraeus and Heraklion) of Greece in relation to the geophysical activity and variations of environmental factors. Dst index and Ap index data, along with cosmic ray intensity data derived from the Athens Neutron Monitor Station (A.Ne.Mo.S.), were used. The study expands from April 2011 to January 2018, covering solar cycle 24. The ANalysis Of Variance (ANOVA) and the superimposed epochs methods were used in order to examine heart rate variations depending on sex. Results revealed that women tend to be more sensitive to physical environmental changes. Statistically significant results are related to the geomagnetic activity but were not obtained for cosmic ray variations.

• Solar and geomagnetic activity (SGA) were associated with lower scores on a dementia screening test. • Increased solar activity was associated with improved global cognitive scores. • Associations between SGA and different aspects of cognitive function were mixed. Studies show that changes in solar and geomagnetic activity (SGA) influence melatonin secretion and the autonomic nervous system. We evaluated associations between solar and geomagnetic activity and cognitive function in the Normative Aging Study from 1992 to 2013. We used logistic and linear generalized estimating equations and regressions to evaluate the associations between moving averages of sunspot number (SSN) and K p index (a measure of geomagnetic activity) and a binary measure for Mini-Mental State Examination (MMSE) scores (≤25 or > 25) and six other cognitive tests as continuous measures, combined into one global composite score and considered separately. A one-IQR increase in same-day SSN and K p index were associated with 17% (95% CI: 3%, 34%) and 19% (95% CI: 4%, 36%) increases in the odds of low MMSE score. We observed small increases in the global cognitive score with increasing SSN, although we observed decreases specifically in relation to the backwards digit span test. Periods of high SGA were associated with cognitive function. SGA may not equally impact all aspects of cognitive function, as evidenced by differences in associations observed for the MMSE, global cognitive score, and individual cognitive tests. Given that much of the pathology of cognitive decline in the elderly remains unexplained, studies specifically targeting decline and with longer follow-up periods are warranted. [ABSTRACT FROM AUTHOR]

Geomagnetic activity shows high degrees of nonlinear variability. The probability distribution has heavy tails, and there are intermittent outliers. This has led to increased interest in forecasting using neural networks and nonlinear regressions, which include time-varying coefficient techniques. Because geomagnetic storms pose the greatest threat to satellites and power grids, there is a particular interest in predicting outlying events. The model proposed here combines two techniques. Neural networks and regressions are trained over moving windows of observations, so that the weights or coefficients adjust to new data. Second, logistic regression is used to predict the periods of high activity, and the cumulative distribution function is used as a causal input in time series and machine learning models. The data set is the Aa index, corrected for secular drift. Forecasting experiments are run over horizons of 1–4 days. The other models include time-varying parameter regressions and a recurrent neural network with fixed weights. The model combining the neural net and logistic regression achieves the most accurate forecast, although the regression is a close second. The ability to predict outliers depends on the width of the moving window. With wider windows, the overall error is lower, but the forecasted values fall into a narrower range, missing the outliers. With narrower windows, the model predicts the outliers better but is vulnerable to calling them at the wrong times, so the average error is higher. Further, while the model achieves more accurate predictions at 1 day, at longer horizons the accuracy deteriorates quite rapidly. • This study combines neural nets with a state transition model to forecast the Aa index. • The state transition model is estimated over the entire prior history. • The neural nets and regressions are trained over moving windows. • The combined model using the neural net achieves the best forecast, although it is only slightly better than the regression. [ABSTRACT FROM AUTHOR]

Solar activity has been linked to biological mechanisms important to pregnancy, including folate and melatonin levels and inflammatory markers. Thus, we aimed to investigate the association between gestational solar activity and pregnancy loss. Our study included 71,963 singleton births conceived in 2002–2016 and delivered at an academic medical center in Eastern Massachusetts. We studied several solar activity metrics, including sunspot number, K p index, and ultraviolet radiation, with data from the NASA Goddard Space Flight Center and European Centre for Medium-Range Weather Forecasts. We used a novel time series analytic approach to investigate associations between each metric from conception through 24 weeks of gestation and the number of live birth-identified conceptions (LBICs) —the total number of conceptions in each week that result in a live birth. This approach fits distributed lag models to data on LBICs, adjusted for time trends, and allows us to infer associations between pregnancy exposure and pregnancy loss. Overall, the association between solar activity during pregnancy and pregnancy loss varied by exposure metric. For sunspot number, we found that an interquartile range increase in sunspot number (78·7 sunspots) in all of the first 24 weeks of pregnancy was associated with 14·0 (95% CI: 6·5, 21·3) more pregnancy losses out of the average 92 LBICs in a week, and exposure in weeks ten through thirteen was identified as a critical window. Although not statistically significant, higher exposure to K p index and to UV radiation across all 24 weeks of pregnancy was associated with more and less pregnancy losses, respectively. While exposure to certain metrics of solar activity (i.e., sunspot number) throughout the first 24 weeks of pregnancy may be associated with pregnancy losses, exposure to other metrics were not. Solar activity is a complex phenomenon, and more studies are needed to clarify underlying pathways. • Solar activity during pregnancy is associated with pregnancy losses. • The direction of the association depends on the solar metric. • Associations do not differ by fetal sex. [ABSTRACT FROM AUTHOR]