The number of sunspots is a key indicator of solar magnetic activity and strongly influences space weather, affecting technological systems and Earth’s environment. This study develops a long-memory statistical framework based on the Auto-Regressive Fractionally Integrated Moving Average (ARFIMA) model to forecast monthly mean sunspot numbers (hbox {SN}_m) for Solar Cycles 25 and 26 using historical data from January 1749 to October 2025. The model parameters are selected using the Bayesian Information Criterion (BIC), and the fractional integration parameter d is estimated via maximum likelihood (hat{d} approx 0.27599), indicating significant long-memory behavior in the series. The selected ARFIMA (3,d,2) model captures the persistent dynamics of solar activity and provides accurate in-sample fitting, with a high correlation coefficient (0.989) between observed and fitted values. Forecast results predict a maximum hbox {SN}_m of 224.7 for Solar Cycle 25 (observed peak: approximately 216 in August 2024) and 179.3 for Solar Cycle 26 around March 2035, suggesting a slightly weaker upcoming cycle. Model performance is evaluated using standard accuracy measures, including RMSE, MAE, and relative error metrics, computed against observed data within a validation framework. The proposed model achieves an RMSE of 3.37 and a SMAPE of 9.25%, indicating improved forecasting accuracy.

ABSTRACT Disentangling anthropogenic signatures of the Anthropocene and the Great Acceleration from natural Holocene climatic oscillations requires high-resolution datasets and transparent computational workflows. This study introduces a “Geopython” ecosystem consisting of two original open-source applications: EssefiSedInterpreter and EssefiCyclo. EssefiSedInterpreter automates sedimentological characterization by integrating image-based morphoscopy (utilizing “Solidity” as a rigorous proxy for grain rugosity) and End-Member Mixing Analysis (EMMA) via Non-Negative Least Squares (NNLS) optimization. Performance validation against industry-standard FRITSCH laser granulometry across 11 samples from Bizerte Lagoon demonstrated a high degree of fidelity, with an average relative error of only 3.06%. EssefiCyclo effectively isolated the non-stationary industrial surges of the Chaffar exoreic system, identifying underlying solar (Schwabe, Hale, Suess), atmospheric (NAO, Mediterranean Oscillation), and oceanographic (AMO) cycles. This integrated ecosystem provides a robust, auditable alternative to proprietary “black-box” software, empowering researchers to transform noisy stratigraphic records into genetically meaningful paleoenvironmental histories. Furthermore, the tool addresses the “geochronological gap” in environments where radiometric dating is sparse. By applying Lomb-Scargle periodograms and a novel “Inverse Cyclostratigraphy” module, the software tunes stratigraphic depth to global deterministic clocks. Applying this to a 78-cm core from Sebkha Mhabeul (380 samples at 2-mm resolution), the tool successfully identified an optimal sedimentation rate of 6.58 years/sample. This enabled the construction of a continuous 2500-year age model, capturing distinct climatic intervals including the Little Ice Age, the Medieval Climate Anomaly, and the Roman Warm Period.

Many organisms have circadian clocks that anticipate the risks and benefits of the predictable 24 h solar cycle. However, the potential functions of circadian clocks in non-photosynthetic bacteria are poorly understood. Here, we show that the Bacillus subtilis circadian clock regulates colony expansion, in concert with key developmental and differentiation pathways that are central to its life cycle. The B. subtilis clock coordinates the spatiotemporal organisation of gene expression within expanding colonies by timing various processes to specific phases (times of day) within distinct colony regions. Our results support the idea that circadian clock-regulation over space, time and colony development in B. subtilis is analogous to circadian regulation of some processes in multicellular eukaryotes such as plants and mammals.

Identifying the ionospheric parameters is one of the important topics in the field of communication support services. In this paper, the Maximum Usable Frequency at 3000 km of the F2 layer (identified as MUF(3000)F2) for high-frequency radio wave propagation has been studied according to its correlation with the Geomagnetic Activity represented by a factor called the Disturbance Solar Time (Dst). Only fifteen disturbed and quiet events of geomagnetic activity associated with the availability of hourly variation of MUF(3000) F2 for three ionosonde station sites have been selected. The three available sites of ionosonde stations are Eglin AFB (30.5° N, 273.45° W), San Vito (40.6° N, 17.8° E), and Dourbes (50.1° N, 4.6° E), and the hourly variations of MUF (3000) F2 were calculated during 2012–2016. The values of the correlation coefficient (CC) were higher and a positive correlation for disturbed events than for quiet events. Geographically, the correlation between the MUF(3000)F2 and the disturbance solar time (Dst) increases with increasing latitude from Eagle AFB to Dourbes. For Eagle AFB and San Vito stations, the values of CC equal (0.473842, -0.21695) for disturbed activity, which relate to positive and negative correlation, respectively. In contrast, for quiet activity, the values of cc equal (-0.36477, 0.15829), respectively. For the high-latitude station (Dourbes), for both disturbed and quiet activity, the correlation between the average value of MUF(3000)F2 and average Dst has a negative correlation (CC=-0.2626, 0.2718). Increasing geomagnetic activity has no significant effect on the average MUF(3000)F2 values. The main shortcomings of this study are the unavailability of the entire dataset and the MUF(3000)F2 related to geomagnetic disturbances, which is represented by the Dst, thereby affecting a comprehensive analysis of the relationship between the above parameters.

Heating and Acceleration of α Particles and Protons Across the Alfvén Critical Surface in Solar Cycle 25

Seasonal patterns in the relationship between gamma emitters in the ground-level atmospheric layer and total atmospheric precipitation in southern Poland (Kraków), 2022 - 2025.

Analog-Based Forecasting of Solar Cycles Using Dynamic Time Warping and Residual Bootstrapping: Real-Time Application to Cycle 25

Coronal Prominence Cavities: A Survey across the Solar Cycle

Global Characteristics of the IBEX Ribbon and Its Temporal Variation: Implications for Relationships with Solar Cycle Variability and the Interstellar Magnetic Field

This study focuses on the dynamics of the subsolar position ( , in Earth radii ) of the magnetopause in response to events originating in corotating interaction regions (CIRs) during the declining phase of solar cycle 24. Based on analyses using the models developed by Shue et al. (1998), Liu et al. (2015) and Lin et al. (2010), we quantify the impact of mechanical and electromagnetic couplings on this boundary. We analyse these dynamics based on the north–south component of the interplanetary magnetic field ( Bz, in nT ), the total interplanetary magnetic field strength ( B, in nT ), the dynamic pressure of the solar wind (Pd, in nPa ), and the magnetic pressure (Pm, in nPa ). Additionally, we consider the normalised solar wind–magnetosphere coupling index (N), derived from the Newell et al. (2007) function and scaled by a normalisation factor of 10⁻⁴. Analysis of the temporal profiles across the different phases of the CIR storms studied reveals progressive and oscillatory variations in the magnetopause's subsolar position ( ). Our results reveal significant compressions, with a reduction in Ro amplitude ranging from 0.9 Re to 5 Re . The main minimum Ro reached during these CIR events studied is 6.4 Re , pushing the magnetopause below the geosynchronous orbit (6.6 Re ). The originality of this study lies in the joint application of cross-correlation, Granger causality, and Bootstrap, an approach that allows dissociating the information-contribution delay (Granger causality) from the time required for the maximum physical adjustment of Ro to the various constraints imposed by solar drivers. Granger causality analysis reveals that predictability is not always immediate: while it is instantaneous for certain drivers, it takes between 14 and 21 minutes for past values of to Pd improve the prediction of Ro during the CIR event of 27 March 2017, and 18 to 20 minutes for the intensity of the interplanetary magnetic field B in the event of 20 January 2016. Regarding physical adjustment, while the responses to and the coupling index (N) are immediate across all six events, the analysis reveals remarkable inertia in the other parameters. The adjustment to the Bz constraint took 33 min to reach its maximum during a specific event. In the six CIR events studied, the adjustment of Ro to the IMF B intensity constraint was slow, with delays ranging from 10 minutes to more than 2 hours (8 min to 130 min). These prolonged delays, particularly well captured by the Lin and Liu models, indicate a hysteresis effect and a slow, global reconfiguration of magnetospheric currents.

Abstract Accurately modeling the solar magnetic field is important for understanding long-term solar activity and space weather, but it is challenging due to limited observations, especially near the Sun’s poles. The surface flux transport (SFT) model simulates how magnetic flux moves across the solar surface and contributes to the polar field, but it parameterizes emerged sunspots as simple symmetric bipolar regions and needs improvement by including more realistic sunspot features. In this study, we reconstruct the century-long evolution of the Sun’s magnetic field, including the polar regions, using an improved SFT model. We incorporate cycle-dependent morphological asymmetry between leading and following sunspots, along with observationally derived tilt angles and sunspot area data for a century (1913–2016), to better represent magnetic flux transport and investigate the impact of asymmetry on polar field development. To study morphological asymmetry, we consider two cases: first, a long-term asymmetry factor calculated from the ratio of leading and following sunspot areas spanning a century; second, the temporal asymmetry factor observed during solar cycle 23 applied to every solar cycle. Our simulated magnetic flux transport with inclusion of morphological asymmetry for both cases gets improved compared to the no-asymmetry case in terms of enhanced low- and midlatitude magnetic flux and matches closely with observations. The simulated polar fields with asymmetry also show a better agreement with polar field observations for most cycles, particularly in capturing the timing of the polar field reversals and the peak amplitude during solar minima, which has severe consequences in solar cycle prediction.

This study investigates the ionospheric and geomagnetic response to Coronal Mass Ejection forcing by analyzing Total Electron Content (TEC) distributions, the relationship between the Interplanetary Magnetic Field (IMF) Bz component and the solar-wind convective electric field (Ey), and the temporal evolution of key geospace parameters during disturbed periods. TEC data derived from GNSS-based Global Ionospheric Maps were used to examine spatial variations and storm-time anomalies in ionospheric electron density. Concurrent solar-wind and IMF measurements obtained from the OMNI dataset were used to compute Ey and assess its correlation with IMF-Bz through statistical and scatter-plot analyses. Time-series plots of Dst, IMF-Bz, solar-wind speed, density, and Ey were constructed to identify the coupling between solar-wind drivers and geomagnetic activity. The results demonstrate that strong southward IMF-Bz enhances Ey, which in turn intensifies geomagnetic disturbances indicated by Dst reductions. Corresponding TEC enhancements and depletions reveal significant restructuring of the ionosphere during storm main and recovery phases. This integrated approach provides improved understanding of solar-wind–magnetosphere–ionosphere coupling and the dynamic behavior of ionospheric TEC under varying geospace conditions. The enhancements and disturbances in the solar wind field due to combined co-rotating interaction region (CIR) and CH HSS influences likely resulted in isolated periods of G1 storm levels late on 23 March and isolated G4 storm levels on 24 March. The Dst index value showed a sudden commencement with a sudden increase to 24nT and then decreased continuously to -163nT on March 24, 2023, which is the largest storm so far in solar cycle 25. The IMF-Bz developed a prolonged and significant southward component reaching a minimum of about -20 nT at 03:00 UT, which corresponds to the peak of the minimum Dst index of -163 nT. Solar wind pressure shows a jump from 1.83 nPa on March 22, 2023, to 14.79 nPa on March 23, 2023. Rapid increases in solar wind dynamic pressure compress the Earth’s magnetosphere and rapidly restructure the electrodynamics within. The enhancement of TEC towards the southern hemisphere high latitude was observed. On March 24, 2023, an enhanced spatial distribution of TEC coverage is over the globe. These all evidences might be the result of the geomagnetic storms.

Physical models aimed to reproduce basic features of the solar sunspot cycle are typically based on the solar dynamo mechanism. Usually qualitative arguments are used to define parameters of the model, among which a challenging component is the nonlinear form of quenching of the α effect governing regeneration of the magnetic field. We propose an approach, in which the functional form of the α quenching is represented by a neural network model embedded into neural differential dynamo equationstrained on observational data. For demonstration, we consider a low-mode dynamo model and find a wide set of α-quenching functions and corresponding dynamo numbers that provide an accurate fit to the average profile of the solar cycle data given by sunspot numbers. Within this set, we observe a strong relationship between the dynamo number and the shape of the α-quenching function indicating that additional magnetic field data or constraints are essential to unambiguously infer parameters of the dynamo model. In our opinion, the neural differential approach opens a prospect for data-driven investigation of the closure problem in dynamo theory.

• Study reconstructs electricity demand profiles in real solar time for Gran Canaria (2023). • Method applies equation of time, longitude correction, and DST offset to legal time data. • Findings: daily peak shifts only 2–4 min; daylight energy share stable at 40–51%. • PV-demand overlap improves slightly (index 0.43–0.55), but evening peak persists. • Partial adaptation scenarios show limited impact compared to full legal time change. • Framework supports evaluation of time-policy reforms and renewable integration strategies. The analysis of electricity demand is usually carried out in legal time, even though this may differ from real solar time due to time zones, geographic longitude, and daylight saving time (DST). This clock–Sun misalignment can distort the physical interpretation of hourly profiles, especially in regions with low solar variability and dominant evening peaks. This study develops a reproducible and physically grounded methodology to reconstruct the twelve monthly average days of 2023 for Gran Canaria in real solar time, applying the equation of time, longitude correction, and seasonal DST offset. All curves are projected onto a uniform 5‑minute grid, allowing coherent comparison between legal time and solar time representations. The results show: (i) a systematic but small shift of the daily peak (≈2–4 min) when expressed in solar time; (ii) a stable daytime energy distribution between 40% and 51%, indicating that social and circadian factors prevail over the solar cycle; (iii) a clear improvement in structural coincidence between demand and synthetic photovoltaic generation, with overlap indices ranging from 0.43 in winter to 0.55 at the beginning of summer; and (iv) partial adaptation scenarios (f = 0.2–0.4) that cause moderate peak advances of 10–25 min, far below the full 60‑minute shift associated with a complete legal change. These results provide a coherent physical framework to assess the impact of eliminating seasonal clock changes in subtropical regions. Beyond the case of the Canary Islands, the approach constitutes a generalizable tool to analyze demand-Sun alignment, estimate realistic social responses to time‑change policies, and support renewable integration strategies in systems with increasing photovoltaic penetration.

New insight from modelling galactic deuterons over changing solar activity

Analysis of the Effect of Solar Activity and Lunar Gravity on Earthquakes During the 24th Solar Cycle (2008-2019)

The Study of Solar Proton Events Characteristics in Solar Cycle 24 Using Principal Component Analysis

Exploration of dependencies of space weather and geomagnetic proxies with thermospheric density enhancement during geomagnetic storms from 2020 to 2024

Quantitative assessment of ionospheric F-region variability under different geomagnetic storm conditions during 24th and 25th solar cycle at a low-mid latitude station, New Delhi

This paper investigates the effects of geomagnetic disturbances that occurred in August 2017, during the declining phase of Solar Cycle 24, when two geomagnetic storms driven by high-speed stream (HSS) and stream interaction region (SIR) structures and associated with HILDCAA intervals took place on 4–6 August and 17–21 August, together with a coronal mass ejection (CME) embedded in the solar wind that impacted the Earth on 22–23 August. The focus of the study is the ionospheric response over the Brazilian sector. For this purpose, we use CADI ionosonde measurements from an equatorial station (Araguatins) and two low-latitude stations (Jataí and São José dos Campos). The empirical model of Fejer and Scherliess (1997) is applied to estimate the equatorial vertical plasma drifts and to assess the impact of prompt penetration electric fields (PPEFs) and disturbance dynamo electric fields (DDEFs) on the F-region ionosphere over Brazil. The results show pronounced variability in the F-layer height parameters ( h ′ F and hpF 2 ) and in the critical frequency ( foF 2 ) throughout August. At the equatorial station, deviations reached approximately ± 80 –160 km ( ± 20 –40%) in h ′ F , ± 160 –200 km ( ± 40 –50%) in hpF 2 , and decreases of about 1–5 MHz in foF 2 . At the low-latitude stations, the corresponding height variations were smaller, typically ± 40 –80 km ( ± 10 –20%), while foF 2 variations remained within the range of -1–5 MHz, with amplitudes decreasing progressively with increasing distance from the magnetic equator. Because storm-time signatures are not always unambiguously identifiable in the raw ionospheric time series, a wavelet-based coherence analysis is employed to quantify how PPEF- and DDEF-related drifts modulate the ionospheric parameters ( h ′ F and foF 2 ) in the time–frequency domain. The time–frequency results support the interpretation that recurrent HSS/SIR structures modulate both the intensity of PPEFs and the equatorial F-layer height. A latitudinal comparison of the wavelet-coherence patterns demonstrates the increasing importance of DDEFs away from the magnetic equator, particularly at Jataí and São José dos Campos. In addition, an analysis of the occurrence of intermediate layers (CIs) is carried out. The CIs, which formed predominantly by detachment from the lower part of the F region followed by downward motion into the ionospheric valley region, exhibited typical virtual heights between 140 and 170 km and peak frequencies between 3 and 4.5 MHz. At Araguatins, the largest number of CI occurrences coincides with geomagnetically disturbed intervals, suggesting that storm-time PPEFs and DDEFs may contribute to the formation or maintenance of CIs near the magnetic equator. At Jataí and São José dos Campos, however, such correspondence is not evident, indicating that additional drivers, such as neutral wind shear, atmospheric tides, and gravity waves, likely play a relatively more important role at those latitudes.