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Yearly sunspot cycle 24 (SC24) activity reached a minimum in December 2019. Timeline for SC25 is explored with data for sunspot numbers (SSNs) and geomagnetic indices (aa/Ap) using our time-tested heuristic methodology not based on any model. We infer SC25 may be as active as SC24, reaching its peak (Rmax) in February 2024 ± 6 months, ruling out Dalton-like minimum in 21st century as well as McIntosh et al. [2020] forecast that “SC25 could have a magnitude that rivals the top few since records began.” Wide range of SC25 forecasts challenges our understanding of solar dynamo operation and reliability of future long-term space weather / climate forecasts. We cannot anticipate whether SC25 may have multiple peaks; no theory is tuned to predict fine structure of a SC. During ascending phase of SC24 a CME from the Sun barely missed the Earth. A direct hit by it could have caused damage of trillions of dollars, shutting down power grid and rendering satellites blind.

Global median empirical model of Total Electron Content (GTEC) is developed driven by re-calibrated sunspot numbers, SSN2, for the quiet geomagnetic conditions (ap

To explain the observed phenomenon of 11-year sunspot cycle with two peaks, we draw attention to the possible role of the turbulent magnetic pumping effects in the solar convection zone (SCZ) at the reconstructing of the toroidal magnetic field that generates the sunspots. Turbulent radial pumping of magnetic field has both kinetic (diamagnetism) and magnetic (vertical advection) contributions. We take into account five physical processes for the combined magnetic reconstructing in deep layers of the SCZ. They are the Ω effect near the tachocline, magnetic buoyancy of the smoothed field, macroscopic diamagnetism, rotational magnetic advection, and deep equatorward meridional circulation. It is the effect of advection with taking into account Sun's rotation that plays a key role in the proposed scenario of magnetic reconstructing. We found that reconstructing of deep toroidal field develops differently in the near-polar and equatorial domains of the SCZ. In the lower half of the near-polar domain, two downward pumping effects (diamagnetism and advection) act against magnetic buoyancy and, as a result, they neutralize magnetic buoyancy and thereby block the toroidal field near the tachocline. At the same time, in the deep layers of the equatorial domain, the rotational advection due to the latitudinal convection anisotropy changes its direction to the opposite (from downward to upward), thereby helping magnetic buoyancy. As a result, this upward magnetic pumping here contributes to the transport of the toroidal field to the solar surface. We call this transport as first upward magnetic advection surge. It ensures a transfer of the deep strong fields to the surface in the latitudes belt of sunspots. Meanwhile, a deep equatorward meridional flow transports the blocked near pole toroidal field in the tachocline from high latitudes to low ones where are favourable conditions for floating up of the magnetic field. Here this belated field is transported upward to the solar surface (the second upward magnetic advection surge). Ultimately, two time-delayed upward magnetic surges may cause on the surface in the “royal zone” the first and second peaks of the sunspots cycle.

Effects on galactic cosmic rays (GCRs) of several heliospheric factors during the minimum phases of the sunspot cycles are studied. Times of maximum GCR intensity are determined for the last five sunspot minima, including the present one, together with the corresponding main heliospheric factors important for the modulation of GCRs in the heliosphere. The quantitative relation between these factors and the solar magnetic field is studied with the poloidal magnetic field of the Sun considered as a governing factor for many heliospheric characteristics during sunspot minima. The dependence of GCR proton spectra on these heliospheric factors for the last five sunspot minima 21/22–24/25 is calculated and discussed. Special attention is paid to the energy at which spectral cross-overs occur for consecutive minima, related to the changing polarity of the heliospheric magnetic field. The long-term observational series on GCR proton modulation at the Earth are considered with respect to the energy of these cross-overs.

Evaluating the coincidence accuracy and time-varying characteristics of global total electron content (TEC) grid data can contribute to the improvement of the performance of global ionosphere maps (GIMs) and provide effective data support and theoretical verification for GIMs model update. This paper applies the global TEC grid data and GPS single-station ionospheric TEC data published by IGS from 1999 to 2020, as well as the F10.7 and SSN data series provided by the World Sunspot Index Data Center in Belgium. Using correlation, time series, and contour chart analyses, the correlation between TEC RMS and F10.7, SSN, and the accuracy-compliant space–time variation characteristics in the global TEC grid data are studied and analyzed. The results show the accuracy of the global TEC grid data is highly correlated with the solar activity intensity. The mean values of the correlation coefficients R between TEC RMS and F10.7, SSN are 0.755 and 0.707, respectively. The internal coincidence accuracy of single station GPS-TEC and global grid TEC is better than 3 TECU and is closely related to the solar activity. Globally, TEC RMS in land and ocean areas have significant differences. In general, the accuracy of the northern hemisphere is significantly higher than that of the southern hemisphere, and the accuracy of land is higher than that of the ocean. Among them, the accuracy of Europe and North America is the highest, the precision of the Pacific region is obviously on the low side, and “double hump” phenomenon can be observed. The accuracy of the global TEC grid data is closely related to the number of stations and satellites. The accuracy of the TEC grid data is higher in areas where the number of stations is dense, or when there are more satellites.

Variations of maximum height of F2 ionospheric layer are analysed over ionospheric stations of Pakistan located at Islamabad (geog. coord. 33.75°N, 72.87°E), Multan (30.18°N, 71.48°E) and Karachi (24.95°N, 67.14°E) during the years, 1987 (LSA), 1990 (HSA) and 1993 (MSA) representing low, high and moderate solar activity years, respectively. Results showed that hmF2 in summer is higher than in winter during LSA and MSA at all stations. However, diurnal pattern is not consistently followed during winters of LSA and MSA. The lowest hmF2 values are observed around sunrise and sunset; whereas, higher values are observed around noon and midnight which may be due to upward and downward plasma drift velocity as diurnal behaviour of hmF2 is similar to diurnal behaviour of E × B drift. No specific latitudinal trend is observed in hmF2 during the period of this study over Pakistan which may be due to the combined effect of E × B drift and energy transferred to ionosphere by atmospheric planetary waves. Solar quiet current seems responsible for the variation of hmF2 over Multan and Islamabad. For Karachi equatorial electrojet seems controlling the daytime hmF2 during LSA. The hmF2 is found to have linear correlation with solar activity and this correlation is stronger with solar index F10.7 as compared to the sunspot numbers. The correlation coefficients for both solar indices are above 80%; whereas, geomagnetic indices Ap and Kp are weakly correlated having correlation coefficients less than 30%. Ionosonde-derived hmF2 are compared with regional model based on expansion of Empirical Orthogonal Function (EOF) with linear and spline interpolation of coefficients of time, seasons, magnetic dip & sunspot numbers and, global model, International Reference Ionosphere (IRI), with International Union of Radio Science (URSI) and Consultative Committee for International Radio (CCIR) options of IRI-2012 and AMTB-2013, SHU-2015 and BSE-1979 sub-models in combination with URSI and CCIR of IRI-2016 versions. The daytime hmF2 values over Pakistan modelled by AMTB of IRI-2016 (with URSI and CCIR) are found to be the most converging of all IRI options during all solar periods. AMTB-2013 also predicted nighttime values with least errors in most cases except during LSA. In addition, IRI showed better equinoctial and annual correlations with ionosonde-derived hmF2 as compared to EOF model. EOF based model showed higher nighttime Mean Absolute Errors (MAE) as compared to IRI. The lowest daytime and nighttime errors in hmF2 are observed over Multan during LSA shown by IRI-2016-AMTB-2013 (using URSI and CCIR) with MAE being 7.8 km and IRI-2016-SHU-2015 (using URSI and CCIR) with MAE being 4.7 km.

The retrodiction and prediction of solar activity are two closely-related problems in dynamo theory. We applied Machine Learning (ML) algorithms and analyses to the World Data Center’s newly constructed annual sunspot time series (1700–2019; Version 2.0). This provides a unique model that gives insights into the various patterns of the Sun’s magnetic dynamo that drives solar activity maxima and minima. We found that the variability in the ~ 11 -year Sunspot Cycle is closely connected with 120-year oscillatory magnetic activity variations. We also identified a previously under-reported 5.5 year periodicity in the sunspot record. This 5.5-year pattern is co-modulated by the 120-year oscillation and appears to influence the shape and energy/power content of individual 11-year cycles. Our ML algorithm was trained to recognize such underlying patterns and provides a convincing hindcast of the full sunspot record from 1700 to 2019. It also suggests the possibility of missing sunspots during Sunspot Cycles −1, 0, and 1 (ca. 1730s-1760s). In addition, our ML model forecasts a new phase of extended solar minima that began prior to Sunspot Cycle 24 (ca. 2008–2019) and will persist until Sunspot Cycle 27 (ca. 2050 or so). Our ML Bayesian model forecasts a peak annual sunspot number (SSN) of 95 with a probable range of 80–115 for Cycle 25 between 2023 and 2025.

Solar activity indices differ over the solar disk, and different activity parameters are not considered to be symmetric between the northern and southern solar hemispheres. In the present paper, the daily data of a set of solar parameters (solar radio flux F10.7, total solar irradiance TSI, plage area PA, coronal index CI, solar flare index SFI, and solar mean magnetic field ǀBǀ) as well as the daily hemispheric sunspot areas (SSAs) and sunspot numbers (SSNs) during a timeframe 1945–2017 (covering almost the last seven solar cycles, 18 24) have been employed to investigate the north-south (N-S) asymmetry of the considered solar parameters based on the dominance of hemispheric distributions of SSAs and SSNs. The N-S asymmetry for each solar parameter has been investigated and the results revealed that it is a significant aspect through different years in the entire period. The grand average of each solar parameter for the northern and southern groups over each solar activity cycle has been calculated to investigate the statistical significance of N-S asymmetry of each solar parameter in each solar activity cycle. The solar cycles 19 and 24 displayed the dominance of the southern F10.7 and PA over the northern one. However, the solar cycle 23 showed the reverse. The grand average of CI displayed the southern preference in the solar cycle 19 while, the northern dominance of CI is revealed for the solar cycle 23. The grand averages of CI demonstrated nearly symmetric distribution in solar cycles 18, and 20–22. The N-S asymmetry of the grand averages of SFI exhibited a southern dominance during solar cycles 21 and 24. On the other hand, the northern preference is observed for the grand average of SFI through the solar cycle 23. The asymmetry of the grand averages of ǀBǀ obviously has the same dominance (sign) of hemispheric sunspot activity indices for the solar cycles 21–24. The periodic behavior of the N-S asymmetry of SSAs, SSNs, F10.7, and ǀBǀ has been investigated using Fast Fourier Transformation. Many mid- and long term periodicities have been detected. We present our results and discuss their possible explanations.

Global empirical models (GMF2 – the F2 layer Global Model) of the critical frequency, foF2, of the ionospheric F2-layer and the peak height, hmF2, are built up with the re-calibrated sunspot number time series, SSN2, for the quiet geomagnetic conditions (ap

Disagreement on information could cause market price volatilities through the channels of gradual information flow, limited attention, and heterogeneous priors. High food price volatilities could incur severe welfare loss. This paper analyzes the effect of sunspots on the volatility of soybeans futures price in a framework of the disagreement theory. Empirically, we use the monthly time series datasets of soybeans futures price and sunspots activities from 1988-2018 to investigate how sunspots affect the volatilities of soybeans futures price by estimating the GARCH, GJR-GARCH, and Markov-switching GARCH models. Our findings can be summarized as: (1) extremely low sunspot activity could lead to both a high level and a high volatility for soybeans futures price; and (2) when considering regime changes, the disagreement level is nonlinear in the high volatility regime in which the high price volatility exists on both extremely low and high sunspot activities.

The problem of optimum solar proxy is important for long-term and/or climatological studies of ionospheric parameters. Here we focus on possibly different optimum solar proxies for different ionospheric parameters, as they are affected by partly different spectral ranges of solar ionizing radiation. We use yearly average values of foF2 and foE of four European stations with long (1976–2014) and high-quality data (Juliusruh, Pruhonice, Rome, Slough/Chilton), and the global total electron content (G-TEC). Four solar proxies are used: F10.7, Mg II, solar Lymna-alpha flux Fα and sunspot numbers. The most important finding is that the optimum solar proxies are different for different ionospheric parameters. The most suitable solar proxy for foF2 is found to be Mg II, whereas for foE F10.7 evidently outperforms Mg II. Fα and sunspot numbers perform slightly worse but none of four solar proxies performs poorly. F10.7 is favored for G-TEC, to some extent surprisingly, as previous results favored rather Mg II.

Sunspots are solar features located in active regions of the Sun, whose number is an indicator of the Sun's magnetic activity. With a substantial increase in the quantity of solar image data, the automated detection and verification of various solar features have become increasingly important for the accurate and timely forecasts of solar activity and space weather. In order to use the high time-cadence SDO/HMI data to extract the main sunspot features for forecasting solar activities, we have established an automatic detection method of sunspots based on mathematical morphology, and calculated the sunspot group area and sunspot number. By comparing our results with those obtained from the Solar Region Summary compiled by NOAA/SWPC, it is found that the sunspot group areas and sunspot numbers computed with our algorithm are in good agreement with the active region values released by SWPC, and the corresponding correlation coefficients for the sunspot group area and sunspot number are 0.77 and 0.79, respectively. By using the method of this paper, the high time-cadence feature parameters can be obtained from the HMI data to provide the timely and accurate inputs for the solar activity forecast.

We studied the cyclic evolution of the latitudinal distribution of solar coronal active regions based on daily images from SOHO EIT for the period 1995-2017. Fully automated software was used, which included the following steps: initial preparation of images in the data series, normalization of histograms and correction of limb brightening, segmentation of images using threshold intensity values obtained from their histograms, scanning of segmented images in heliographic coordinates and obtaining profiles of latitudinal distribution of coronal active regions for each image of the data series. From the output data, we obtained a temporary change in the latitudinal distribution profiles and the migration of activity centers on the solar disk. From the period of minimum activity to the next minimum in both hemispheres, activity centers begin to migrate from high latitudes towards the equator. At the same time, the general center of activity repeatedly changes the direction of migration. The latitudinal distribution of the so-called presence factor of coronal active regions closely resembles the magnetic butterfly diagram, which proves their direct causal relationships. Variations in the presence factor of coronal active regions are correlated with cyclic variations in the sunspot daily numbers.

The variability of NmF2 during solar minima of solar cycle 21–22, 22–23 and 23–24 has been studied for two low latitude stations, Karachi (Pakistan) and Okinawa (Japan), as both stations are situated at the Equatorial Ionization Anomaly (EIA) crest region. Diurnal, seasonal and annual behaviour of variability has been investigated using relative standard deviation approach. At both the stations, a direct relation of variability (CV) with Smoothed Sunspot Numbers (SSN) is noted which is opposite to the results found by many authors who have worked on different solar activity periods. It is suggested that the E-layer is responsible for this direct relation as an increase in the E-layer ionization with decrease in SSN for solar minimum has also been noted for Karachi in our previous work (Talha et al., 2019). The interaction of tides and waves with the E-layer might be responsible for the increase in ionization of the E-layer and the decrease in variability in the F-layer. Also, the night-time variability is observed to be higher than the daytime variability during minima as expected due to the low mean NmF2 or large deviation during night-time. Very prominent post-midnight peaks and not very well shaped post-sunset peaks are also noticed at both stations. Besides the mentioned peaks, a small increase in variability during mid-day is noticed which might be due to the flow of fountain plasma from the equator to the EIA crest region. Seasonal comparison of variability showed high variability during daytime in winter and during night-time in equinox while lowest variability is noted in summer. Lowest variability at post-midnight is noted in winter instead of summer which might be due to the complex interaction of waves and tides with the lower ionosphere. Small difference in variability between both stations is also noticed due to difference in their longitude. Geomagnetic field configuration at both stations is different which in turn causes change in the electron density and also difference in variability at both stations.

This paper explores the role of bubbles in an overlapping-generations economy where some agents are more productive than the others. Due to missing credit markets, productive and unproductive agents cannot trade their financial assets to achieve mutual benefit, making the economy to perform below its potential. Introducing bubbles on the one hand crowds out some productive resources as it does in the current literature. It on the other hand may divert resources away from unproductive agents to productive ones. We find that bubbles are growth enhancing when the unproductive agents’ productivity level lies within an interval. Furthermore, in sharp contrast to the existing literature, the equilibrium bubble size is stable. This finding enables us to construct a two-state stationary sunspot equilibrium in which one state is associated with small bubbles and low growth whereas the other one has large bubbles and high growth.

We present an update of the changes in space weather/space climate at Earth orbit using sunspot number (SSN) timeline (1700–2018), geomagnetic indices aa/Ap, solar polar magnetic field, interplanetary magnetic field (IMF) and galactic cosmic ray (GCR) flux in the stratosphere at high latitudes. The Cycle 24 is close to solar minimum, expected in 2020. The baseline of aa index increases monotonically from 1900 to 1986 and declines steeply afterwards, solar polar magnetic field decreases systematically for the last three cycles (22–24) as do SSNs at cycle peaks. Livingston and Penn (2009) note a long term weakening of maximum magnetic field in sunspots since 1992. They expect SSNs for the Cycle 25 to peak at 7 (a steep decline in solar activity) leading to Maunder-like minimum, in contrast to prediction of several colleagues of a Dalton minimum. The North-South asymmetry in solar polar field is pronounced for the decay phase of cycles 23, 24, itseems to change sign after the Cycle 21. GCR flux in the stratosphere is greater that in 1965 and increasing, pointing to an enhanced radiation exposure in future for the passengers on transpolar flights, the astronauts on the space station as well as those travelling to and staying on the Moon and the Mars on prolonged missions; the assets in space would have to be hardened for safety from increased radiation. We speculate about the connection between the Earth climate and changes in solar activity, inferring that the science of the Earth climate change is not settled yet.

The Northern Song Dynasty was an important and prosperous dynasty in the history of China, and it existed during a period of climate abnormality. Climate change research for the Northern Song Dynasty era has significance for understanding the interaction between agricultural civilizations in the central plains and nomadic populations in northern China, transfer of the economic and cultural centers of China, and the vicissitudes of the Northern Song Dynasty. There is currently considerable disagreement regarding climate change in the Central Plain during the Northern Song Dynasty era. Many precious and valuable historical documents and records about the Northern Song Dynasty have been collected, and abundant records of sunspot activity, cold and warm weather, drought and flood events have been compiled. Using the Mann-Kendall test, wavelet analysis, R/S analysis, and frequency analysis etc. mathematical statistics methods, sunspot activity, cold and warm events, and drought and flood events were quantitatively reconstructed. There are 15 sunspot maximum years and 16 sunspot minimum years, the cycle length of sunspot activity is 8–14 years, and the average cycle length is 11 years. Hot years account for 11.3% of the total years; warm years account for 12.7%; cold years account for 20.7%; and freezing cold years account for 3.3%. Mann-Kendall test results show that cold and warm variations are natural fluctuations, and there is no indication of abrupt climate change during the Northern Song Dynasty. Morlet wavelet analysis indicates that there are weak high-frequency oscillations and short oscillation periods with three years before 1052 AD, and there are oscillation periods of six years and clear alternations between warmth and cold during 1060-1120 AD. R/S analysis indicates that the Hurst index (H) of cold and warm index series is 0.6155, and the fractal dimension (D) is 1.3845. Since 0.5

In this paper, we use non-parametric kernel approach to estimate the probability density function (pdf) of auroral-night and naked-eye-sunspot series over multi-century timescale. We selected the events observed in medieval epoch, and auroral records from low geographical latitude ( Results confirm the existence of strong connection between auroras and sunspot activity, especially from 11th to 16th century. Indeed, a high correlation degree r = 0.72 is obtained for the period AD 800–1500 between the two pdf of sunspots ( p d f S ) and auroras ( p d f A ) for bandwidth h = 10 years, and exceed 0.8 for h > 43 years. However, we notice a time-shift between the two density functions. To calculate it, we use the cross-correlation technique, and we find τ = −5.9 years, that is strangely close to the half of solar cycle period. It is very important to note that our results revealed that the high frequency of low latitude auroras occurs before the maximum of naked-eye sunspots activity, and not afterward, on contrary to what is expected. The pdf curves show multiple peaks occurring at quasi-periodic times and show clearly the three grand minima of solar activity: Oort, Wolf and Sporer. In auroral-night data, the mean period at 95% CI obtained is: T ‾ = 61 ± 7 y e a r s . Using power spectrum analysis, we observe clearly a strong signal of 60 years period that is a new evidence of the existence of such cycle. More importantly, we identified a cycle of 262 years period in the sunspot data, and a new oscillation of 310 years in auroral-night data. These two cycles appear clearly in the pdf curves using optimized bandwidth obtained by the direct plug-in approach of Sheather and Jones.

The irregularity of the solar activities based on sunspot numbers (SSNs) and areas (SSAs) over the solar disk has been considered. More activities phenomena occurred in one of the solar hemispheres than the other at the same time, which they are referred to as the North-South (N-S) asymmetry of solar activity. Daily averages of geomagnetic indices aa, Ap, Kp, and Dst over the period 1967–2016 have been examined according to the asymmetrical distribution of both solar hemispheric activities. The possible connection between the geomagnetic activity disturbances and the sign of non-uniformity of solar activity, i.e. the N-S asymmetry for each geomagnetic index has been confirmed. The dependence of the sign of geomagnetic disturbances on the solar activity cycle, has been examined. We have classified the considered data into two groups according to the activity of northern (N) or southern (S) solar hemisphere. The solar cycles 20 and 24 have northern hemisphere dominance. These activities shifted from northern to southern hemisphere in solar cycles 21, 22, and 23. The geomagnetic disturbances exhibited significant asymmetrical states at different periods. The most significant northern and southern peaks occurred at/near the minimum of the solar cycle or in periods of descending phase of the solar cycle. The geomagnetic activity has southern dominance during solar cycle 22 and it favoured the northern activity during solar cycle 23. The dependence of the geomagnetic activity disturbance of aa, Ap, Kp, and Dst indices over the solar activity cycle is confirmed and the sign of the asymmetry changes from one solar cycle to another.

The study on the 1.3–1.7 yr period of the solar and geomagnetic activities is very important for understanding the possible physical processes in the solar-terrestrial coupling system. The sunspot is the most prominent magnetic field structure in the solar photosphere, and the Ap index is an important indicator for the global geomagnetic activity level. The 1.3–1.7 yr period for the sunspot number and the geomagnetic Ap index is obtained by the synchro-squeezing wavelet transform, and the phase relationship between them is studied by the cross-correlation analysis. The main results are as follows: (1) The 1.3–1.7 yr period of the geomagnetic Ap index and sunspot number exhibits an intermittent evolutionary characteristics, and changes continuously with the time; (2) the geomagnetic Ap index has a higher periodic component in the odd solar cycles than the neighboring even solar cycles, which is characterized by fluctuations; (3) the phase relationship between the geomagnetic Ap index and the sunspot number is not always invariant, in most cases the geomagnetic Ap index lags behind the sunspot number, except in the 18th and 22th solar cycles.

In this work we continue studying possible reasons for temporal variability observed in correlation links between characteristics of the lower atmosphere and solar activity phenomena at the multidecadal time scale. Temporal variations of correlation coefficients between troposphere pressure at extratropical latitudes and sunspot numbers are compared with the evolution of the large-scale circulation forms according to the Vangengeim-Girs classification, as well as the characteristics of the stratospheric polar vortex and global temperature anomalies. The results obtained show that temporal variability of solar activity/galactic cosmic ray (SA/GCR) effects on troposphere pressure (the development of extratropical baric systems) is characterized by a roughly 60-year periodicity and closely related to changes in the regime of large-scale circulation which accompany transitions between the different states of the polar vortex. It was suggested that the character of SA/GCR effects depends on the polar vortex strength influencing the troposphere-stratosphere coupling. It was shown that the evolution of the polar vortex may be associated with global temperature variations, with a possible reason for these variations being long-term changes of total solar irradiance.

The spectral decomposition of time series obtained from ancient rock records can be used to study the similarity between the dynamics of present-day and past climate systems. A high-resolution periodicity analysis of luminance and lamina thickness of lacustrine stromatolites in the Ebro Basin (northeast of Iberian Peninsula) reveals a significant signal of interannual and decadal climatic variability in the Miocene. This is one out of very few works that presents the use of spectral analysis to estimate the potential of stromatolite lamination as multiple-scale recorders of climate parameters. The effects of precipitation and evaporation variations on stromatolite lamination have been detected at three orders of cyclicity based on textural and high-resolution stable-isotope analyses (C and O) obtained in prior studies. These analyses also revealed that the light and dark simple lamina couplets are identified with annual cycles (third-order isotopic cycles). In the present study, the spectral analysis results obtained through different paths in five stromatolite specimens reveal significant periods in the power spectrum at around 2.5, 3.7, 5, 7, 10, and 22 years. These cycles can be correlated with the typical oscillation bands of different climate-related agents. The 2.5-year period corresponds to the Quasi Biennial Oscillation (QBO), or to the biennial component of the El Nino-Southern Oscillation (ENSO), or to the North Atlantic Oscillation (NAO). The 3 to 5 and 5 to 7-year bands can be linked to ENSO or NAO variability (second-order isotopic cycles). The 8 to 11-year bands fit the 11-year Schwabe (first-order isotopic cycles) and 22 to 23-year fit the 22-year Hale sunspot cycles. Thus, the stromatolite growth was controlled by ENSO, NAO, and solar activity cycles. The close relationship between these climate-related agents makes it difficult to specify the dominant agent controlling the stromatolite growth. Nevertheless, the significant periods obtained from this study, within interannual (2.5, 3.7, 5, 7 years), decadal (10, 22 years), and even multidecadal bands (37–42 years), support the existence, and concurrence, of ENSO and NAO precursors during the early and middle Miocene.

Using the recently converted to digital format heliophysics catalogues of the Ebro Observatory published in the 1930s, we analyse simultaneously the temporal variation and asymmetry of two different solar structures located at different layers of the solar atmosphere: sunspots and solar plages. In particular, we do the research for all the types of sunspots and plages, including the daily and relative frequencies over the solar cycle. The data were catalogued using the sunspot Cortie classification and a solar plage classification scheme proposed by the Ebro Observatory, which group the phenomena by size and shape. For all types of both sunspots and plages, we observe a decrease in their frequency up to the end of solar cycle 16 and an increase over the beginning of solar cycle 17. Furthermore, we note that small sunspot groups are more likely to happen than bigger groups, although single big spots dominate near the solar minimum. The daily frequency of solar plage occurrences shows that there is not a dominance of compact or scattered solar plages. The North-South occurrence distribution of every type in both sunspots and solar plages shows an asymmetry during the solar cycle: in its declining phase, such asymmetry is directed to the north, while in the beginning of a new cycle is directed to the south.

Korean chronicles have a large amount of observational records of natural phenomena, including astronomical and meteorological events over two thousand years. Here we examine the correlation of solar activity and climate change from historical sunspot and frost records in the Korean chronicles. There are 42 sunspot records in Goryeo Dynasty (918–1392 CE) and 13 records in Joseon Dynasty (1392–1910 CE). The sunspot records in Goryeo Dynasty show a periodicity in good agreement with the well-known solar activity of 11 years. Korean sunspot records suggest that the solar activity in Joseon Dynasty decreased compared with that in the previous ∼500 years. In order to examine the long-period variation of solar activity, we include Chinese historical sunspot records in our analysis to supplement the lack of Korean records, and find a new ∼240-yr long-period solar activity from the power spectral analysis. Korean chronicles also have about 700 frost records during the last millennium. We investigate these frost records and find a sign of cooling down that can be interpreted as climate change during the last millennium. We also find ∼240-yr cooling period from the historical frost records, which is well in accord with that of solar activity. Therefore, we conclude that the solar activity has decreased during the last one thousand years and also has a long-term variation of ∼240 years.

European hydroclimate shows a high degree of variability on every time scale. The variability is controlled by natural processes such as Atlantic ocean cycles, changes in solar activity, volcanic eruptions and anthropogenic factors. This contribution concentrates on the solar influence on European precipitation, a relationship which has been documented by a large body of published case studies. Here we are concentrating on the period 1901–2015 for which we compare sunspot data with monthly precipitation series of 39 European countries by calculating Pearson correlation coefficients for a multi-year cross-correlation window. The coefficients have been mapped out across Europe with the aim to identify areas in which solar activity may have influenced precipitation. Results show that February precipitation in Central and Western Europe yields the strongest solar response with coefficients reaching up to +0.61. Rainfall in June–July is equally co-driven by solar activity changes, whereby the solar-influenced zone of rainfall shifts from the British Isles towards Eastern Europe during the course of summer. Other months with noteworthy solar responses are April, May and December. On a decadal scale, the correlation between precipitation and solar activity in central Europe appears to be mostly positive, both statistically and by visual curve comparison. Yet, best positive correlations coefficients of February, June, July and December are typically reached when the solar signal lags rainfall by 1.5–2 years. Taking into account cause and effect, it is suspected that increases in Central European rainfall are actually triggered by the solar minimum some 3–4 years before the rainfall month, rather than the lagging solar maximum. Similar lags of a few years occur between solar activity and the solar-synchronized North Atlantic Oscillation (NAO) due to memory effects in the Atlantic. The literature review demonstrates that most multidecadal studies from Central Europe encountered a negative correlation between solar activity and rainfall, probably because short time lags of a few years are negligible on timescales beyond the 11 year solar Schwabe cycle. Flood frequency typically increases during times of low solar activity associated with NAO- conditions and more frequent blocking.

The international reference ionosphere, IRI, and its extension to plasmasphere, IRI-Plas, models require reliable prediction of solar and ionospheric proxy indices of solar activity for nowcasting and forecasting of the ionosphere parameters. It is shown that IRI prediction errors could increase for the F2 layer critical frequency foF2 and the peak height hmF2 due to erroneous predictions of the ionospheric global IG index and the international sunspot number SSN1 index on which IRI and IRI-Plas models are built. Regression relation is introduced to produce daily SSN1 proxy index from new time series SSN2 index provided from June 2015, after recalibration of sunspots data. To avoid extra errors of the ionosphere model a new solar activity prediction (SAP) model for the ascending part of the solar cycle SC25 is proposed which expresses analytically the SSN1 proxy index and the 10.7-cm radio flux F10.7 index in terms of the phase of the solar cycle, Φ. SAP model is based on monthly indices observed during the descending part of SC24 complemented with forecast of time and amplitude for SC25 peak. The strength of SC25 is predicted to be less than that of SC24 as shown with their amplitudes for eight types of indices driving IRI-Plas model.

Ionospheric variation from the climatological mean has been extensively studied due to its effect on ionospheric high frequency radio propagation. This work reports foF2 variation at Ouagadougou (geogr. 12oN, 1.8oW, dip ∼3°), complementing works that have been done at this station. Nighttime variability is higher than daytime and varies with season but with no consistent pattern. There is an earlier post-midnight peak variability in June solstice (around 0100LT) and occurred between 0400 and 0500LT in other seasons for all sunspot classifications except solar maxima. In this study, we have paid attention to features in the ascending/decending phase of the sunspot cycle and we observed that nighttime ionospheric variability may not always decrease with increasing sunspot number, particularly in the ascending phase. The mechanisms for the difference between observations in the ascending and descending phases could not be identified.

A group of successive evolutionary images of a sunspot were observed on 4th March 2014 at the Ca II H (396.85 nm) line by the telescope on board of the Hinode satellite. The calculated oscillation period of the sample point in the umbra is 149.75 s by using the Jurkevich (JK) method. A proper averaged value of the intensity profile is selected as the steady background radiation, then the distribution of the extreme values of oscillations in the umbra is analyzed by a statistical method. The results show that the valley values follow a normal distribution, while the peak values satisfy a partial normal distribution. The distribution of these extreme values indicates that the 3 min oscillation of the umbra may be caused by the propagation of a traveling wave with a period of about 5 min in the umbra. The variation of light intensity caused by the traveling wave may be proportional to the square of the displacement of the traveling wave, resulting in a 3 min period of the light intensity, which is one half of the period of traveling wave.

Various ionospheric vertical scale heights (VSH) including, the Chapman (Hm), VSH at upper ionosphere (VSHUP) and 500 km (VSH500) derived using COSMIC radio occultation (RO) retrieved electron density profiles during a complete solar cycle (2006–2016) are presented in this research. VSH show distinct latitudinal variations and solar-activity dependencies. VSH follow the geomagnetic equator with a longitudinal structure irrespective of the season and year, although mid and high latitudes show higher values and irregular variations in low (2006–2010) and moderate-to-high (2011–2016) sunspot years during the daytime hours (1300 LT-1500 LT). The longitudinal structure of VSH500 appears only in moderate-to-high sunspot years, which is an important observation reported for the first time in this communication. Diurnal variations of Hm at equatorial latitudes show higher values starting from ∼0400 LT to ∼2300 LT with a post-sunset peak. However, an absence of the post-sunset peak is seen in VSHUP and VSH500 which is probably due to the altitudinal gradients of vertical drifts that increase (decrease) below (above) the F-layer peak during evening pre-reversal enhancements. The reduced drifts above the F-layer peak thereby, suppresses the post-sunset peak in VSH. Concurrent and large-scale structures in VSH500 and VSHUP at mid and high latitudes in summer hemispheres during June and December solstice seasons are reported for the first time, which occurred possibly due to the long-duration exposure to the Sun's strong radiation during summer seasons. A one-to-one correlation exists between the Chapman scale heights and peak height of the F2 layer (hmF2) at equatorial latitudes in different seasons, while moderate correlation is seen between them away from the equatorial latitudes. These presented scale heights at a global scale are very significant, particularly, for future empirical modeling studies and the long-term availability of COSMIC RO retrieved electron density profiles allowed us to present these scale heights.

The Solar Influences Data Analysis Center (SIDC) issued a new version (version 2) of the sunspot number data in July 2015. The 13-month smoothed monthly sunspot number from the new version is used for the first time to research the relations among the feature parameters of solar cycles under the bimodal distribution for the modern era cycles (10–23), and, their physical implications are discussed. These relations are utilized to predict the maximum amplitude of solar cycle 25. Cycle 25 is predicted to start in October 2020 and reach its maximum amplitude of 168.5 ± 16.3 in October 2024, thus, it should be stronger than cycle 24 but weaker than cycle 23.

Possible mechanism of solar activity effect on scattering radiation as well as the intensity of exchange processes in the different layers of the troposphere is discussed in this paper. In particular the response of the earth's atmosphere scattering and refraction characteristics to the 11 year variations of the sunspots' formation activity is considered. Analysis of the radiation data show that one may observe significant growth of the mean annual values of diffuse radiation while a total solar activity decreasing in certain years. The effect of solar activity on the diffuse radiation fluctuations is most pronounced over a long time periods, the duration of which is more than 11 years. The effect of any connection becomes invisible at the shortest time intervals when high-frequency perturbations are imposed.

Accepted: 2017-08-24, 資料番号: SA1180297000

A morphological examination of the Kitt Peak photospheric magnetic maps has been made over three sunspot cycles in order to study the morphology of unipolar magnetic regions and sunspots. Unipolar magnetic regions (positive and negative) are a series of weak, large-scale longitudinal bands, extending from 0° to 60° in latitude and alternatively aligned in longitude. The first finding is that unipolar regions grow and decay with the sunspot cycle and thus are likely to be a part of the basic solar (dipolar) magnetism, not old active regions located below 30° in latitude (as have long been considered). The second finding is that positive pores and single spots (coalesced pores, often called ‘isolated’ spots or ‘independent’ spots) occur in a positive unipolar region (vice vera). Thus, the unipolar regions could be the source of single spots. The third finding is that a pair (positive and negative) of dense clusters of pores, single spots and large spots (a coalesced single spots) occur at each side of the boundary of neighboring (positive and negative) unipolar regions, forming pairs of spots across the boundary; in fact, pairs of spots do not occur in the middle of a unipolar region. The boundaries of unipolar regions are tentatively identified as the Hale boundary, where solar activities (including solar flares) occur). Thus, it is suggested that the presently accepted magnetic tube theory may need a new consideration.

The skewness of the monthly distribution of GSE latitudinal angles of Interplanetary Magnetic Field (IMF) observed near the Earth (Sk) is found to show anti-correlation with sunspot activity during the solar cycles 20–24. Sk can be considered as a measure of the predominant polarity of north-south component of IMF (Bz component) in the GSE system near 1 AU. Sk variations follow the magnitude of solar polar magnetic fields in general and polarity of south polar fields in particular during the years 1967–2020. Predominant polarity of Sk is found to be independent of the heliographic latitude of Earth. Sk basically reflects the variations of the solar dipolar magnetic field during a sunspot cycle. It is also found that IMF sector polarity variation is not a good indicator of the magnitude changes in solar polar magnetic fields during a sunspot cycle. This is possibly due to the influence of non-dipolar components of the solar magnetic field and the associated north-south asymmetries in the heliospheric current sheet.

In the present work we show that it is possible to predict the maximum sunspot number for a particular solar cycle from the maximum value of the solar dipole magnetic field of the previous cycle. Based on the measured dipole field maximum, we determine the geomagnetic activity in the upcoming solar minimum during the intervals when the Earth is not exposed to CME and HSS influences. The physical meaning of the relationship between the geomagnetic activity in the solar activity minimum and the maximum value of the solar dipole magnetic field is that the basic factor determining the geomagnetic activity during the minimum is not the heliospheric current sheet thickness but the physical parameters of the slow solar wind in this period. Then, based on the established relationship between the average geomagnetic activity at the specified minimum and the next solar maximum, we can predict the sunspot maximum of the next solar cycle.

Spring-Autumnal asymmetry (SA asymmetry) from years 1873–2010 in the geomagnetic activity is investigated based on the geomagnetic indices (aa, Ap and Kp). Results have shown that in general the SA asymmetry of the geomagnetic activity appears to be alternation, except for the interval during which the change of dominant solar dipole magnetic field polarity occurs. Our study implies that both the polarity of the main solar dipole field and the north-south asymmetry of the sunspot area in the two solar hemispheres control the strength of the south component (Bs) of the interplanetary magnetic field (IMF) near the Earth and the resulting SA asymmetry of the geomagnetic activity in the corresponding seasons. A simple sector structure model is devised to establish the relationship between the polarity of solar main dipole magnetic field, the IMF Bs component and the corresponding SA asymmetry in the geomagnetic activity. This is confirmed by examining the solar wind parameters from the spacecraft observations during the recent decades.

In this paper we revise our prediction of solar activity using a solar background magnetic field as a proxy by the inclusion of eigen vectors of solar magnetic waves produced by quadruple magnetic sources, in addition to the principal eigen modes generated by two-layer dipole sources (Zharkova et al., 2015). By considering the interference of two dipole and one quadruple waves we produce the revised summary curve for the last 400 years accounting for the additional minima of solar activity occurred at the beginning of 19th (Dalton minimum) and 20th centuries. Using the dynamo model with meridional circulation and selecting the directions of circulation for quadruple waves, we estimate the parameters of quadrupole waves best fitting the observations in the past grand cycle. The comparison shows that the quadruple wave has to be generated in the inner layer of the solar convective zone, in order to provide the additional minima observed in 19 and 20 centuries, thus, naturally accounting for Gleissberg centennial cycle. The summary dynamo wave simulated for the dipole and quadruple sources reveals much closer correspondence of the resulting summary curve derived from the principal components of magnetic field variations to the solar activity oscillations derived from the average sunspot numbers in the current grand cycle.

Well-preserved siliciclastic biolaminites from the Neoproterozoic Wuqiangxi Formation (ca. 810–715 Ma) in South China show submillimeter-scaled couplets that consist of alternating dark and light laminae. The laminar couplets have been interpreted of annual origin, and the dark and light laminae mainly record warm spring to summer and cold autumn to winter deposition, respectively. Power spectrum and evolutionary fast Fourier transform (FFT) analyses of the laminar couplet thickness variations and geochemical series (Al, Th, Ba/Ti, Cu/Ti, Zn/Ti, V/Ti and U/Ti) revealed prominent periodicity of 10.0–11.4 yr and 18.9–25.6 yr. These two coherent periodic modes match well with the 11-yr Schwabe sunspot cycle and 22-yr solar Hale cycle, respectively. The observed layering pattern is thus interpreted as recording solar induced climate changes that may have modulated sedimentation, microbial growth and biomass production in shallow marine environments between fair-weather and storm-wave bases. Preservation of the sunspot cycles may have been facilitated by quiet depositional environment, microbial mat protection, and early diagenetic silicification. The documented Neoproterozoic cyclicity, in combination with previously reported examples, implies the stability of sunspot periodicity since the Paleoproterozoic. The presence of stable sunspot cycles in the upper Wuqiangxi Formation also suggests that the solar activity did not change significantly at the dawn of the Sturtian glaciation.

Space weather reflects multiple causes. There is a clear influence for the sun on the near-earth environment. Solar activity shows evidence of chaotic properties, implying that prediction may be limited beyond short horizons. At the same time, geomagnetic activity also reflects the rotation of the earth's core, and local currents in the ionosphere. The combination of influences means that geomagnetic indexes behave like multifractals, exhibiting nonlinear variability, with intermittent outliers. This study tests a range of models: regressions, neural networks, and a frequency domain algorithm. Forecasting tests are run for sunspots and irradiance from 1820 onward, for the Aa geomagnetic index from 1868 onward, and the Am index from 1959 onward, over horizons of 1–7 days. For irradiance and sunspots, persistence actually does better over short horizons. None of the other models really dominate. For the geomagnetic indexes, the persistence method does badly, while the neural net also shows large errors. The remaining models all achieve about the same level of accuracy. The errors are in the range of 48% at 1 day, and 54% at all later horizons. Additional tests are run over horizons of 1–4 weeks. At 1 week, the best models reduce the error to about 35%. Over horizons of four weeks, the model errors increase. The findings are somewhat pessimistic. Over short horizons, geomagnetic activity exhibits so much random variation that the forecast errors are extremely high. Over slightly longer horizons, there is some improvement from estimating in the frequency domain, but not a great deal. Including solar activity in the models does not yield any improvement in accuracy.

We analyze the Greenwich catalog data on areas of sunspot groups of last thirteen solar cycles. Various parameters of sunspots are considered, namely: average monthly smoothed areas, maximum area for each year and equivalent diameters of groups of sunspots. The first parameter shows an exceptional power of the 19th cycle of solar activity, which appears here more contrastively than in the numbers of spots (that is, in Wolf’s numbers). It was found that in the maximum areas of sunspot groups for a year there is a unique phenomenon: a short and high jump in the 18th cycle (in 1946–1947) that has no analogues in other cycles. We also studied the integral distributions for equivalent diameters and found the following: (a) the average value of the index of power-law approximation is 5.4 for the last 13 cycles and (b) there is reliable evidence of Hale's double cycle (about 44 years). Since this indicator reflects the dispersion of sunspot group diameters, the results obtained show that the convective zone of the Sun generates embryos of active regions in different statistical regimes which change with a cycle of about 44 years.

The long term solar activity dependencies of ionospheric F1 and F2 regions’ critical frequencies ( f 0 F 1 and f 0 F 2 ) are analyzed for the last four solar cycles (1976–2015). We show that the ionospheric F1 and F2 regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F1 region critical frequency ( f 0 F 1 ) peaks at the same time with the small SG numbers, while the f 0 F 2 reaches its maximum at the same time with the large SG numbers, especially during the solar cycle 23. The observed differences in the sensitivity of ionospheric critical frequencies to sunspot group (SG) numbers provide a new insight into the solar activity effects on the ionosphere and space weather. While the F1 layer is influenced by the slow solar wind, which is largely associated with small SGs, the ionospheric F2 layer is more sensitive to Coronal Mass Ejections (CMEs) and fast solar winds, which are mainly produced by large SGs and coronal holes. The SG numbers maximize during of peak of the solar cycle and the number of coronal holes peaks during the sunspot declining phase. During solar minimum there are relatively less large SGs, hence reduced CME and flare activity. These results provide a new perspective for assessing how the different regions of the ionosphere respond to space weather effects.

Due to the important role of temperature in the global climate system and energy cycles, it is important to investigate the spatial-temporal change patterns, causes and implications of annual maximum (Tmax) and minimum (Tmin) temperatures. In this study, the Cloud model were adopted to fully and accurately analyze the changing patterns of annual Tmax and Tmin from 1958 to 2008 by quantifying their mean, uniformity, and stability in the Wei River Basin (WRB), a typical arid and semi-arid region in China. Additionally, the cross wavelet analysis was applied to explore the correlations among annual Tmax and Tmin and the yearly sunspots number, Arctic Oscillation, Pacific Decadal Oscillation, and soil moisture with an aim to determine possible causes of annual Tmax and Tmin variations. Furthermore, temperature-related impacts on vegetation cover and precipitation extremes were also examined. Results indicated that: (1) the WRB is characterized by increasing trends in annual Tmax and Tmin, with a more evident increasing trend in annual Tmin, which has a higher dispersion degree and is less uniform and stable than annual Tmax; (2) the asymmetric variations of Tmax and Tmin can be generally explained by the stronger effects of solar activity (primarily), large-scale atmospheric circulation patterns, and soil moisture on annual Tmin than on annual Tmax; and (3) increasing annual Tmax and Tmin have exerted strong influences on local precipitation extremes, in terms of their duration, intensity, and frequency in the WRB. This study presents new analyses of Tmax and Tmin in the WRB, and the findings may help guide regional agricultural production and water resources management.

International audience; We investigate the extent to which standard one sector RBC models with positive externalities and variable capacity utilization can account for the large hump-shaped response of output when the model is submitted to a pure sunspot shock. We refine the Benhabib and Wen (2004) model considering a general type of additive separable preferences and a general production function. We provide a detailed theoretical analysis of local stabilities and local bifurcations as a function of various structural parameters. We show that, when labor is infinitely elastic, local indeterminacy occurs through Flip and Hopf bifurcations for a large set of values for the elasticity of intertemporal substitution in consumption, the degree of increasing returns to scale and the elasticity of capital-labor substitution. Finally, we provide a detailed quantitative assessment of the model and conclude with mixed results. We show that although the model is able theoretically to generate a hump-shaped dynamics of output following an i.i.d. sunspot shock under realistic parameter values, the hump is too persistent for the model to be considered fully satisfactory from an empirical point of view.

The analysis of turbulent processes in sunspots and pores which are self-organizing long-lived magnetic structures is a complicated and not yet solved problem. The present work focuses on studying such magneto-hydrodynamic (MHD) formations on the basis of flicker-noise spectroscopy using a new method of multi-parametric analysis. The non-stationarity and cross-correlation effects taking place in solar activity dynamics are considered. The calculated maximum values of non-stationarity factor may become precursors of significant restructuring in solar magnetic activity. The introduced cross-correlation functions enable us to judge synchronization effects between the signals of various solar activity indicators registered simultaneously.

We present a combined analysis of the applications of the weighted horizontal magnetic gradient (denoted as WG M in Korsos et al. (2015)) method and the magnetic helicity tool (Berger and Field, 1984) employed for three active regions (ARs), namely NOAA AR 11261, AR 11283 and AR 11429. We analysed the time series of photospheric data from the Solar Dynamics Observatory taken between August 2011 and March 2012. During this period the three ARs produced a series of flares (eight M- and six X-class) and coronal mass ejections (CMEs). AR 11261 had four M-class flares and one of them was accompanied by a fast CME. AR 11283 had similar activities with two M- and two X-class flares, but only with a slow CME. Finally, AR 11429 was the most powerful of the three ARs as it hosted five compact and large solar flare and CME eruptions. For applying the WG M method we employed the Debrecen sunspot data catalogue, and, for estimating the magnetic helicity at photospheric level we used the Space-weather HMI Active Region Patches (SHARP’s) vector magnetograms from SDO/HMI (Solar Dynamics Observatory/Helioseismic and Magnetic Imager). We followed the evolution of the components of the WG M and the magnetic helicity before the flare and CME occurrences. We found a unique and mutually shared behaviour, called the U-shaped pattern, of the weighted distance component of WG M and of the shearing component of the helicity flux before the flare and CME eruptions. This common pattern is associated with the decreasing-receding phases yet reported only known to be a necessary feature prior to solar flare eruption(s) but found now at the same time in the evolution of the shearing helicity flux. This result leads to the conclusions that (i) the shearing motion of photospheric magnetic field may be a key driver for solar eruption in addition to the flux emerging process, and that (ii) the found decreasing-approaching pattern in the evolution of shearing helicity flux may be another precursor indicator for improving the forecasting of solar eruptions.

The solar atmosphere exhibits a diverse range of wave phenomena, where one of the earliest discovered was the five-minute global acoustic oscillation, also referred to as the p-mode. The analysis of wave propagation in the solar atmosphere may be used as a diagnostic tool to estimate accurately the physical characteristics of the Sun's atmospheric layers.In this paper, we investigate the dynamics and upward propagation of waves which are generated by the solar global eigenmodes. We report on a series of hydrodynamic simulations of a realistically stratified model of the solar atmosphere representing its lower region from the photosphere to low corona. With the objective of modelling atmospheric perturbations, propagating from the photosphere into the chromosphere, transition region and low corona, generated by the photospheric global oscillations the simulations use photospheric drivers mimicking the solar p-modes. The drivers are spatially structured harmonics across the computational box parallel to the solar surface. The drivers perturb the atmosphere at 0.5 Mm above the bottom boundary of the model and are placed coincident with the location of the temperature minimum. A combination of the VALIIIC and McWhirter solar atmospheres are used as the background equilibrium model.We report how synthetic photospheric oscillations may manifest in a magnetic field free model of the quiet Sun. To carry out the simulations, we employed the magnetohydrodynamics code, SMAUG (Sheffield MHD Accelerated Using GPUs).Our results show that the amount of energy propagating into the solar atmosphere is consistent with a model of solar global oscillations described by Taroyan and Erdelyi (2008) using the Klein-Gordon equation. The computed results indicate a power law which is compared to observations reported by Ireland et al. (2015) using data from the Solar Dynamics Observatory/Atmospheric Imaging Assembly.

The knowledge about future solar activity is necessary to plan our space-based missions. As yet, several prediction models (statistics- or dynamo-based) have been developed to forecast the peak smoothed sunspot number (SSN) of the upcoming solar cycle. Many of these data-based prediction models require sunspot number until the end of nth solar cycle to predict the peak of the solar cycle n + 1. However, one prefers to have the predictions well in advance. We propose a new data-based model that can provide information about the peak SSN (or amplitude) of solar cycle n ​+ ​1, and sum of peak SSN of solar cycle n ​+ ​2 and n ​+ ​3 ​at the end of each nth solar cycle. The solar cycles are paired using even-odd cycles, therefore in this model n is allowed to take even number. We used recently updated, Version-2, daily and monthly sunspot-number data. The area under the curve of each nth solar cycle [An] is estimated and used in the model together with its length and peak SSN [ S max n ]. We noticed that difference in the area under the curve of solar cycles n and n + 1 can be used to predict the summation of peak SSN of n + 2 and n + 3 solar cycles (i.e., S max n + 2 + S max n + 3 ). We have tested this prediction model with both daily and monthly sunspot numbers. Our model predicts; S max 24 + S max 25 ​= ​219.7 ​± ​31 and S max 26 + S max 27 ​= ​229.4 ​± ​31. As the peak SSN of solar cycle 24 is known, we get S max 25 ​= ​103.3 ​± ​15. Further, model suggest that the solar cycle 26 and 27 would be similar or slightly stronger than solar cycle 24 and 25.

According to the scheme of action of the solar dynamo, the poloidal magnetic field can be considered a source of production of the toroidal magnetic field by the solar differential rotation. From the polar magnetic field proxies, it is natural to expect that solar Cycle 25 will be weak as recorded in sunspot data. We suggest that there are parameters of the zonal harmonics of the solar surface magnetic field, such as the magnitude of the $\ell$=3 harmonic or the effective multipole index, that can be used as a reasonable addition to the polar magnetic field proxies. We discuss also some specific features of solar activity indices in Cycles 23 and 24., Comment: 20 pages, 10 Figures, accepted in JSTP

There is increasing interest in finding the relation between solar activity and climate change. In general, fractal properties may be observed in the time series of the dynamics of complex systems, such as solar activity and climate. This study investigates the relations among solar activity, geomagnetic activity, and climatic regime shift by performing a multifractal analysis. To investigate the change in multifractality, we apply a wavelet transform to time series. The change in fractality of the sunspot number (SSN) correlates closely with that of the solar polar field strength. For the SSN and solar polar field strength, a weak multifractality or monofractality is present at the maximum SSN, minimum SSN, and maximum solar polar field strength. A strong multifractality is present two years before the maximum SSN. The climatic regime shift occurs when the SSN increases and the disturbance of the geomagnetic activity is large. At the climatic regime shift, the changes in the fractality of the Pacific Decadal Oscillation (PDO) index and changes in that of the solar activity indices corresponded with each other. From the fractals point of view, we clarify the relations among solar activity, geomagnetic activity, and climatic regime shift. The formation of the magnetic field of the sunspots is correlated with the solar polar field strength. The solar activity seems to influence the climatic regime shift. These findings will contribute to investigating the relation between solar activity and climate change.

The El Nino No. 3 area index (5°S∼ 5°N, 150°W∼ 90°W) and yearly sunspot number (SSN) from 1408 to 1978 are used to investigate the influence of solar activity on the El Nino/Southern Oscillation (ENSO), through periodicity analysis, cross wavelet transform (XWT), cross correlation and ensemble empirical mode decomposition (EEMD) analyses. The solar activity period, the Hale period, and the Gleissberg period are determined in the El Nino index time series, but of weak statistical significance. Cross correlation analysis of the index with SSN, and that of its low-frequency components decomposed by EEMD clearly indicate that solar activity may take effect on the ENSO, and such an impact should undergo an accumulation procedure (phase delay). XWT also indicates the existence of the impact. It is found that the index is negatively correlated with SSN when SSN is large during a certain long-term interval, and positively when SSN is small. Strong El Nino is inferred to be taken place in decade(s) to come.