The solar cycle, also referred to as the solar magnetic activity cycle, represents a nearly periodic change in solar activity occurring approximately every 11 years, as evidenced by the observation of sunspot numbers. The terms solar maximum and minimum denote the phases of peak and trough sunspot activity, respectively. Solar Cycle 25 commenced in December 2019, starting with a minimum smooth sunspot number of 1.8, and is projected to persist until the conclusion of December 2030. In this study, we employed the FB Prophet Prediction Model, utilizing sunspot data collected from January 1749 to March 2025 (spanning over 276.25 years), to forecast sunspot numbers for the latter half of Solar Cycle 25 (69 months). We forecast sunspot numbers for the remainder of Solar Cycle 25 and the entirety of Solar Cycle 26 (through 2036). This study employed the FB Prophet model on 276 years of sunspot data (January1749-March2025) to generate two forecasts: one for the remainder of Solar Cycle 25, and a second for the early portion of Solar Cycle 26, extending through 2036. Our model predicts that Solar Cycle 25 will peak in early 2025 and that Solar Cycle 26 will peak in mid-2034, both with a smoothed sunspot number of approximately 118. A comparison between our predicted outcomes and the NOAA published forecast data demonstrates the effectiveness and suitability of the FB Prophet Prediction model for predicting sunspot activity during Cycle 25. The coefficient of determination, commonly referred to as ([Formula: see text]), assesses the extent to which the model reflects the observed outcomes and signifies the percentage of variance in the dependent variable that can be forecasted based on the independent variables within the model. Its value is 89.23%, which demonstrates the model's high level of predictive accuracy. This demonstrates the good agreement results and also confirms the effectiveness and suitability of the FB Prophet Prediction model for predicting sunspot activity during Cycle 25.

Abstract Some of the most interesting insights into solar physics and space weather come from studying radio emissions associated with solar activity, which remain inherently unpredictable. Hence, a real-time triggering system is needed for solar observations with the versatile new-generation radio telescopes to efficiently capture these episodes of solar activity with the precious and limited solar observing time. We have developed such a system, Solar Triggered Observations of Radio bursts using MWA and Yamagawa (STORMY) for the Murchison Widefield Array (MWA), the precursor for the low frequency telescope of upcoming Square Kilometre Array Observatory (SKAO). It is based on near-real-time data from the Yamagawa solar spectrograph, located at a similar longitude to the MWA. We have devised, implemented, and tested algorithms to perform an effective denoising of the data to identify signatures of solar activity in the Yamagawa data in near real-time. End-to-end tests of triggered observations have been successfully carried out at the MWA. STORMY is operational at the MWA for the routine solar observations, a timely development in the view of the ongoing solar maximum. We present this new observing framework and discuss how it can enable efficient capturing of event-rich solar data with existing instruments, like the LOw Frequency ARray (LOFAR), Owens Valley Radio Observatory - Long Wavelength Array (OVRO-LWA) etc., and pave the way for triggered observing with the SKAO, especially the SKA-Low.

Abstract Ionospheric plasma interaction with charged satellite surfaces can lead to a substantial increase in orbital drag. In this context, natural events related to solar activity can have a detrimental effect on a satellite's lifespan and introduce uncertainty in orbital trajectory predictions. This work investigates the variations in charge drag coefficient during solar minimum and solar maximum conditions for Low Earth Orbits with altitudes in the range 300–1,000 [km]. Two months, August 2008 and January 2014, near the solar minimum and solar maximum activities are selected to represent variations of ion and electron densities and temperatures during the solar cycle. The simulations are performed using pdFOAM, an electrostatic particle‐in‐cell code. The results show that the charge drag coefficient increases with altitude. Variations are more pronounced during solar minimum than maximum. The variation of the charge drag coefficient depends significantly on the total ion density as well as the percent fraction of lighter ions . In the lower part of the ionosphere (300 [km]), dominated by , the charge drag coefficient , varies in the range . At higher altitudes 1,000 [km], dominated by , especially during the night, it varies in the range , with the extreme values being related to the solar minimum. For both solar minimum and solar maximum conditions, the charge drag force can become significant compared to the neutral drag force and it is 2 times higher at altitude 1,000 [km].

Abstract We started measuring geomagnetically induced current (GIC) in substations around Tokyo, Japan in 2017 to study the GIC effects on power systems. We defined a period with GIC continuously exceeding 3 A as a GIC event to analyze the long-term data. This threshold is sufficiently above the noise level of the measurement data to clearly distinguish the events. Approximately 90% of the GIC events selected using this threshold have duration of less than twenty minutes. The GIC events between February 2018 and December 2024 were analyzed for the GIC data at SFS substation because GIC amplitude observed at SFS was the largest among the four substations where GIC measurements have been conducted. Occurrence of the GIC events with large amplitude and long duration increased according to increase of solar activity towards solar maximum of cycle 25. Most of the GIC events occurred during significant variations in the geomagnetic field associated with magnetic storms regardless of their main or recovery phase although the GIC event with the largest amplitude occurred associated with a sudden commencement (SC) at the start of initial phase of the storms, such as the storm on 10 October 2024. The relationship between the peak H-component geomagnetic variation (∆H) of the magnetic storm and the absolute value of a peak GIC (|A peak |) showed a good correlation with a correlation coefficient of 0.92. The GIC event with the longest duration were recorded in the main phase of the storm on 10 May 2024, which had a minimum provisional Dst of − 406 nT. We also found an example of a long-duration GIC event related to a SC caused by a high-density solar wind region, which was not accompanied by a magnetic storm. Graphical Abstract

Abstract The water escape from Mars to space could be in the form of hydrogen and oxygen ions as driven by solar wind–Mars interactions. Although oxygen ion escape has been extensively investigated, the H + escape rate was measured only at solar minimum. To determine the impacts of solar activity on the ionospheric H + escape rate, we report the observational results from the Tianwen-1 spacecraft at solar maximum. The cold dense ionospheric ion outflows through the magnetotail have an equal energy acceleration process, consistent with the characteristics of ambipolar electric field acceleration. The escape rate of planetary cold H + through the magnetotail is estimated to be ∼2 × 10 23 s −1 , a value substantially lower than the neutral hydrogen escape rate, and the H/O ratio (∼0.3) of the tailward escaping ions (H + , O + and O 2 + ) is below the stoichiometric ratio of water. These results indicate the ionospheric H + outflow plays a minimal role for the water loss on Mars across solar cycles. To assess the contribution of H + escape to total hydrogen loss, future analysis must target the pickup H + escape rate within the magnetosheath.

Empirical relationships explore and understand an advanced effectively methodology for predicting maximum temperature (Tm) in regions with different climatic conditions based on solar irradiance (SI) readings taken from NASA/POWER for the period 2014–2024. Using seasonal and annual daily means, the SI-Tm correlations during the four seasons (winter, spring, summer, and autumn) and annual cycle were investigated in six cities (Basra, Shanafiya, Baghdad, Rutba, Kirkuk and Shakhan) in Iraq using quadrate and cubic polynomial regression models. These models provided strong fit lines between the data points for SI and Tm, which effectively capture the seasonal (R2>0.4 in winter and summer and >0.8 in spring and autumn) and annual daily Tm (R 2 > 0.9) as a predictor variable. The results show that Iraq experiences high SI and extreme Tm, especially in the southern regions. In contrast, the northern provinces have lower SI and Tm values due to higher altitudes and increased weather activity. This study offers valuable information for policymakers and planners to highlight the potential for solar energy generation and distribution in accordance to climatic conditions.

Abstract The occurrence time of the equatorial ionization anomaly (EIA) crest, denoted as T EIA , is a sensitive indicator of low‐latitude ionosphere–thermosphere coupling. However, its systematic modulation over multiple solar cycles has remained unclear. Using Global Ionospheric Maps (GIM, 2003–2022), ICON/MIGHTI neutral winds (2019–2022), the HWM‐93 model, and Equatorial Electrojet (EEJ) data and models, we quantify the solar‐cycle modulation of T EIA and elucidate the governing physical mechanisms. Our 20‐year analysis reveals that T EIA advances (delays) on average by ∼0.2 hr during solar minimum (maximum), potentially following the interannual variation of solar activity. This modulation is possibly driven by dual‐driver mechanisms: (a) Enhanced equatorial electric fields (EEF, proxied by EEJ) during solar maximum strengthen the equatorial plasma fountain, extending the crests' position and prolonging their development; and (b) the amplitude of the meridional wind at ∼300 km anti‐correlates with solar activity, with weakened wind during solar maximum slowing poleward diffusion. This work elucidates the physical mechanisms of T EIA variability, offering new insights into low‐latitude ionospheric dynamics and practical implications for space‐weather prediction.

Abstract Accurate prediction of solar flares is essential for space weather warnings and safeguarding technological infrastructure. This study proposes a dual-stage flare prediction framework leveraging the full-disk flare index (FI). In the first stage, FI is decomposed into long-term trend and short-term disturbance components via a “trend-disturbance” decomposition strategy. The iTransformer model independently forecasts each component, which is then fused to generate high-fidelity FI predictions. The second stage develops a regression-classification architecture that maps predicted FI values to flare intensity levels, enabling comprehensive full-disk flare forecasting. Experimental results indicate that the decomposition strategy improves performance across all flare classes, reducing the mean absolute error of FI prediction to 19.066 and achieving a TSS of 0.639 and an F1 score of 0.649 for M-class flares. Tested from the solar minimum in 2019 through the 2024 solar maximum, the framework surpasses the operational forecasting capabilities of leading space weather prediction centers such as SWPC and SEPC, successfully delivering reliable 72 hr flare warnings during 2024 May events. The dual-stage framework introduces an innovative approach to improving the accuracy and reliability of flare prediction, offering a valuable reference for forecasting extreme solar activity events.

Abstract We present observations of a rare configuration of Mercury's magnetosphere in response to sub‐Alfvénic upstream conditions, driven by an interplanetary coronal mass ejection (ICME) that impacted the planet on 1 May 2013. Using data from the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft, supported by a global three‐dimensional magnetohydrodynamic (MHD) simulation of the event, we demonstrate that Mercury's magnetospheric response during this interval was distinct from the typical super‐Alfvénic state. During the sub‐Alfvénic upstream conditions, MESSENGER measured a distorted magnetotail with a depleted southern magnetotail lobe. An MHD simulation closely reproduces these observations, providing a plausible global context for the reconfiguration of Mercury's magnetosphere under sub‐Alfvénic conditions. The simulation predicts that a pair of Alfvén wings formed during this event, redirecting magnetic flux and plasma within the magnetosphere. The interplanetary magnetic field orientation during this event was primarily sunward/dawnward, generating asymmetric Alfvén wings with respect to the flow direction, in contrast to previously observed north–south wing configurations at the planet. Using Solar Orbiter observations in the inner heliosphere, we estimate that the solar wind is sub‐Alfvénic approximately 2.5 times per Earth year near solar maximum, with intervals lasting between 10 s and 12 hr. Studies of these rare, sub‐Alfvénic solar wind‐magnetospheric interactions provide valuable insights into exoplanet–stellar wind interactions under similarly sub‐Alfvénic conditions where in situ observations are not available.

Abstract A new daily composite of the solar flare index (SFI) and the hemispherically‐resolved versions (hSFI) are presented for 1937 to 2024. The data set confirms that the northern hemisphere (NH) dominated solar flare activity during Solar Cycles 17 to 21, but that the southern hemisphere has dominated from Solar Cycle 22 to present. That said, the highest SFI value occurred in the NH during the recent superstorm of May 2024. In sunspot activity, the “Gnevyshev‐Ohl rule” shows that the sum of sunspot numbers during even‐numbered cycles is related to those of adjacent odd‐numbered cycles. A similar rule appears to apply to SFI. The “Gnevyshev gap” phenomenon where solar maximum activity sometimes has two peaks separated by up to 1–2 years of a gap is confirmed for SFI. Although our data set represents the longest continuous daily data set for solar flare activity to‐date, it is known that stronger solar flare events occurred before 1937. Therefore, a brief discussion of earlier solar flare events in the historical record is also provided for context. The statistics of the SFI and hSFI series are compared to other solar and geomagnetic activity indices, including the May and October 2024 solar storms. Statistical analysis of past geomagnetic storms confirms they are more frequent during active cycles and less frequent during solar minima. Strong geomagnetic storms are also more likely to occur during the positive phase of a 1.7 year's quasi‐biennial oscillation in solar activity. The likelihood of low‐magnetic latitude aurorae seems to have a 30 year periodicity component.

Abstract The quiescent or dynamic nature of fine-scale raylike features in the Sun corona, observed in visible light, is still an open question. Here, we show that most of the daily and hourly periodic variations in visible light brightness of the high corona (up to 15 R ⊙ ) are aligned to the tip of streamers and are consistent with the periodicity of plasma release from simulations of tearing-induced magnetic reconnection at the heliospheric current sheet. The areas in which we detect periodicities can be used as tracers of nonquiescent fine coronal rays. This also allows their distinction from coronal rays more likely to be real quiescent features or associated with smaller and/or faster unresolved brightness variations. In the low- and middle-corona (down to 1.4 R ⊙ ) similar brightness variations are observed along loop-like and cusp-like features marking boundaries of streamers, which then connect to radial features in the high corona. This suggests the presence of additional mechanisms in the low- and middle-corona periodically releasing density structures in the solar wind. The periodicity distributions show a solar cycle modulation with shorter periods (smaller structures) during solar maximum. Periodicities are observed within streamers during solar minimum but are visible at all latitudes, even extending radially from the poles, during solar maximum.

This paper proposes a convolutional Long Short-Term Memory (ConvLSTM) network integrated with multi-channel features dedicated to ionospheric total electron content (TEC) forecasting. To improve generalization, solar, and geomagnetic activity indices are added as auxiliary channel inputs. The model is built upon an Encoder–Decoder (ED) architecture enhanced with residual connections and convolutional channel projection, which collectively improve the synergy among its core components. Based on this framework, we developed ED-ConvLSTM-Res, a multi-channel feature-based global ionospheric TEC prediction model. Comprehensive accuracy evaluation and comparative tests were carried out using datasets from the solar minimum year of 2019 and the current solar maximum year of 2024. The results indicate that the proposed model consistently achieves strong predictive performance compared with other models, along with a significantly enhanced feature representation capability. Specifically, the Root Mean Square Errors (RMSE) of the ED-ConvLSTM-Res model’s predictions in 2019 and 2024 are 1.28 TECU and 5.28 TECU, respectively, while the corresponding Mean Absolute Errors (MAE) are 0.87 and 3.87, and the coefficients of determination (R2) are 0.95 and 0.94. In the current high solar activity year 2024, the proposed model achieves error reductions of 13.6% in MAE and 11.6% in RMSE compared with the Center for Orbit Determination in Europe (CODE)’s one-day-ahead forecast product, c1pg. These results confirm that the proposed model not only outperforms the ConvLSTM model without additional indices and c1pg but also exhibits strong generalization capability, maintaining stable performance with low errors under both high and low solar activity conditions.

Abstract. We extended the Linearized ozone scheme – LINOZ in the ICON (ICOsahedral Nonhydrostatic) – ART (the extension for Aerosols and Reactive Trace gases) model system to include NOy formed by auroral and medium-energy electrons in the upper mesosphere and lower thermosphere, and the corresponding ozone loss, as well as changes in the rate of ozone formation due to the variability of the solar radiation in the ultraviolet wavelength range. This extension allows us to realistically represent variable solar and geomagnetic forcing in the middle atmosphere using a very simple ozone scheme. The LINOZ scheme is computationally very cheap compared to a full middle atmosphere chemistry scheme, yet provides realistic ozone fields consistent with the stratospheric circulation and temperatures, and can thus be used in climate models instead of prescribed ozone climatologies. To include the reactive nitrogen (NOy) produced by auroral and radiation belt electron precipitation in the upper mesosphere and lower thermosphere during polar winter, the so-called energetic particle precipitation indirect effect, an upper boundary condition for NOy has been implemented into the simplified parameterization scheme of the N2O/NOy reactions. This parameterization, which uses the geomagnetic Ap index, is also recommended for chemistry-climate models in the CMIP6 experiments. With this extension, the model simulates realistic “tongues” of NOy propagating downward in polar witner from the model top in the upper mesosphere into the mid-stratosphere with an amplitude that is modulated by geomagnetic activity. We then expanded the simplified ozone description used in the model by applying LINOZ version 3. The additional ozone tendency from NOy is included by applying the corresponding terms of the version 3 of LINOZ. This NOy, coupled as an additional term in the linearized ozone chemistry, led to significant ozone losses in the polar upper stratosphere in both hemispheres which is qualitatively in good agreement with ozone observations and model simulations with EPP-NOy and full stratospheric chemistry. In a subsequent step, the tabulated coefficients forming the basis of the LINOZ scheme were provided separately for solar maximum and solar minimum conditions. These coefficients were then interpolated to ICON-ART using the F10.7 index as a proxy for daily solar spectra (UV) variability to account for solar UV forcing. This solar UV forcing in the model led to changes in ozone in the tropical and mid-latitude stratosphere consistent with observed solar signals in stratospheric ozone.

We investigate the occurrence characteristics and amplitude-frequency relationships of Pc5 ultra-low frequency (ULF) waves (1.67–6.7 mHz) using 30 years of GOES magnetic field data (1995–2025) from GOES-8 to GOES-18. An enhanced CLEAN algorithm, employing iterative Hanning peak model fitting and subtraction, identified 27,279 radial, 26,145 azimuthal, and 31,259 parallel wave events in the Mean Field-Aligned coordinate system. Radial and parallel waves exhibit peak amplitudes between 9–15 MLT, driven by solar wind dynamic pressure, while azimuthal and parallel components dominate in the 15–21 MLT sector, consistent with Kelvin-Helmholtz instability. Strong power-law relationships (R^2 ge 0.85) between amplitude and frequency are observed for radial and azimuthal components in dawn and dusk sectors, with weaker correlations for the parallel component (R^2 le 0.24). These relationships vary with solar wind conditions, with radial components showing robust power-law fits under strong and moderate conditions (R^2 ge 0.93). ULF wave occurrence rates peak during solar maxima, correlating strongly with solar wind parameters (R^2 ge 0.73), and exhibit quasi-biennial oscillations (QBOs)–short-term (1.5–4 year) modulations linked to solar dynamo processes. High-pass filtered data show strong correlations with dynamic pressure (R^2 ge 0.85). These findings resolve discrepancies in prior studies, highlighting the interplay of solar cycle, QBOs, and MLT-dependent drivers in Pc5 ULF wave dynamics, with implications for radiation belt dynamics and space weather forecasting.

Abstract As the Sun approaches the peak of its 25th activity cycle, intensified ionospheric spatial gradients near the equatorial ionization anomaly (EIA) crest pose critical challenges to GNSS positioning accuracy, particularly in low-latitude regions. Traditional network RTK systems, which rely on linear interpolation models (LIMs) to approximate ionospheric correlations between reference stations, inadequately resolve nonlinear spatial gradients along ionospheric pierce point (IPP) trajectories, a key source of residual errors in double-differenced ionospheric (DDI) delays. To address this limitation, we introduce a Nonlinear Interpolation Model (NIM) that explicitly incorporates satellite-specific gradients along IPP trajectories. By dynamically detrending spatially nonlinear ionospheric terms, NIM improves ionospheric delay interpolation accuracy. Evaluations across mid-latitude and low-latitude networks show NIM reduces DDI interpolation errors by 30–40% compared to LIMs. Statistical analyses under diverse ionospheric conditions highlight NIM’s enhanced error distribution characteristics, particularly during sunset and post-sunset transitions when gradients peak. Notably, during the extreme May 2024 geomagnetic storm, NIM achieved below 2 cm RMS positioning accuracy in Hong Kong, a region historically prone to large ionospheric gradients. These improvements translate to measurable gains: a 10% higher ambiguity resolution success rate, 30% faster convergence times, and horizontal/vertical positioning precision of 1.1/3.8 cm. By integrating IPP trajectory gradients into spatial modeling, NIM provides a scalable framework for robust RTK operations in gradient-prone regions. This advancement supports reliable centimeter-level positioning during solar maxima.

Abstract This study analyzes energetic neutral atom (ENA) spectral properties across distinct regions of globally distributed flux (GDF) sky maps, using Interstellar Boundary Explorer data from a full solar cycle, corrected for time dispersion. By time-shifting the data to the heliosheath using GDF source distances from D. B. Reisenfeld et al., we achieve a more accurate representation of heliosheath GDF energy spectra. We quantify ENA spectral characteristics, heliosheath line-of-sight-integrated proton pressure, and heliosheath proton temperature, comparing these to solar wind properties at 1 au and interplanetary scintillation-derived solar wind data. Our findings show that the spectral index is generally anticorrelated with heliosheath proton temperature and pressure, except in the central tail, where a partial positive correlation is observed. The lowest spectral index values occur when high-latitude heliosheath regions are dominated by fast solar wind from polar coronal holes. The south pole exhibits the flattest energy spectra due to plasma heating from both fast solar wind and a late-2014 pressure pulse. The central tail shows shorter variability (5–6 yr) for spectral index and heliosheath proton temperature, while proton pressure follows the 11 yr solar cycle. Most spectral shapes exhibit a “knee” distribution, peaking during solar maximum, with an “ankle” shape observed only at the south pole during solar cycle transitions. Asymmetry in proton pressure in the lobes is driven by the draping effect of the local interstellar magnetic field. This study provides insights into the energetic properties of GDF across the heliosphere, enhancing our understanding of the heliospheric environment.

Abstract We present an unprecedented simulation of how two large-scale heliospheric transients—a coronal mass ejection (CME) and a corotating stream interaction region—collide, producing a dramatic increase in the complexity of the CME due to formation of mesoscale flux ropes. These structures are captured for the first time by a numerical simulation using high-resolution numerical grids. The circumstances that lead to the formation of these complex structures occur during solar maximum. At the time of the solar maximum taken for this study, 2014 September, the heliospheric current sheet is vertically inclined running over the poles, allowing the CME to impact a preceding slow-fast stream interaction region. The simulation is performed with the Alfvén Wave Solar Atmosphere Model (or AWSoM), with which we initiate a fast CME from active region (AR) 12158 by applying a Gibson–Low magnetic flux rope. Magnetic reconnection within the leading extremity of the CME results in the formation of mesoscale flux ropes, which contain sufficiently strong magnetic fields (∼30 nT) to affect planetary magnetospheres. Finally, we use a tetrahedral configuration of four virtual probes, corresponding to the Space Weather Investigation Frontier mission concept, to show that the mission can uniquely resolve the spatial characteristics and temporal evolution of reconnecting current sheets within the CME, as well as the resulting mesoscale structures.

Context. Time-evolving magnetohydrodynamic (MHD) coronal models driven by a sequence of time-evolving photospheric magnetograms deliver more realistic results than traditional quasi-steady-state models constrained by a static magnetogram. The fully implicit time-evolving coronal model COCONUT performs efficiently enough for real-time coronal simulations during solar minimum. Significant challenges persist in modelling the more complex coronal evolutions of solar maximum scenarios, however. Aims. During solar maxima, the coronal magnetic field is more complex and stronger, and coronal structures evolve more rapidly than during solar minima. Consequently, time-evolving MHD coronal modelling of solar maxima often struggles with poor numerical stability and low computational efficiency. We enhanced the numerical stability of the time-evolving coronal model COCONUT to mitigate these issues with the aim to evaluate the differences between the time-evolving and quasi-steady-state coronal simulation results, and to assess the impact of the spatial resolution on global MHD coronal modelling of solar maxima. Methods. After enhancing the positivity-preserving property of the time-evolving coronal model COCONUT, we employed it to simulate the evolution of coronal structures from the solar surface to 0.1 AU in an inertial coordinate system over two Carrington rotations around the solar storms in May 2024. These simulations were performed on unstructured geodesic meshes containing 6.06, 1.52, and 0.38 million (M) cells to assess the impact of grid resolution. We also conducted a quasi-steady-state coronal simulation that treated the solar surface as a rigidly rotating spherical shell to demonstrate the impact of the emergence and cancellation of the magnetic flux in global coronal simulations. A comparison with observations further validated the reliability of the efficient time-evolving coronal modelling technique. Results. We demonstrate that incorporating the evolution of the magnetic field in the inner boundary conditions can significantly improve the fidelity of global MHD coronal simulations around a solar maximum. A simulated magnetic field strength using a refined mesh with 6.06 M cells can be stronger by more than 40% than that in a coarser mesh with 0.38 M cells. A time step of 5 minutes and a mesh containing 1.5 M cells can effectively capture the evolution of large-scale coronal structures and small-sized dipoles. Thus, the fully implicit time-evolving model COCONUT shows promise for accurately conducting real-time global coronal simulations of solar maxima. This makes it suitable for practical applications such as daily space-weather forecasting.

Abstract Solar active regions (ARs) host the majority of solar eruptions. Studying the evolution and morphological features of ARs is significant for understanding the physical mechanisms of solar eruptions and beneficial for forecasting hazardous space weather. This work presents an automated DBSCAN-based solar active region detection (DSARD) method for ARs observed in magnetograms. DSARD is based on an unsupervised machine learning algorithm called density-based spatial clustering of applications with noise (DBSCAN). This method is employed to identify ARs in magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory from 2010 to 2023. To avoid duplicate detections and minimize projection effects, we focus on a longitudinal range of ±6° from the central meridian of the solar disk. Within this range, we obtain the distributions of the number, area, magnetic flux, tilt angle, and butterfly diagram of bipolar ARs in latitudes and time intervals during solar cycle 24, as well as their drift velocities. Most of these statistical results align with previous studies, which validates our method. The asymmetry indices of the number of ARs, cumulative area, and total unsigned magnetic flux indicate that the northern hemisphere dominated in terms of AR activity during most of solar cycle 24, except near solar maximum. Additionally, we analyze the dipole tilt angles of ARs in solar cycle 24 and the rising phase of solar cycle 25, revealing that 13% and 16% of ARs, respectively, violate Hale’s law.

Abstract The solar wind and the interplanetary magnetic field (IMF) are of significant importance, as they affect the plasma environment and dynamic processes in the planetary magnetosphere. This study statistically analyzes the solar wind parameters upstream of Earth (ACE), Mars (MAVEN), Jupiter (Ulysses, Galileo, Juno), and Saturn (Cassini) and their solar activity phase (solar maximum, descending, minimum, and ascending phases) dependence. The heliolatitude variations are validated using Ulysses observations. Results show that the radial magnetic field decays more gradually than expected (r −2), and the IMF intensity (B) decreases more rapidly at higher heliolatitudes. The solar wind proton density (N p ) near Mars is significantly higher than expected, while the solar wind speed (V) is lower. The IMF spiral angle (SA) aligns well with the Parker SA upstream of planets and at high heliolatitudes, except for Mars. Martian anomalies may stem from mass loading by pickup ions (contributing to the increased N p and lower V) and the IMF bending effect caused by Martian current systems. The B and solar wind dynamic pressure are higher during solar maximum compared to solar minimum. Additionally, the V, plasma beta, and Alfvén Mach number exhibit larger values during the solar descending phase compared to the solar ascending phase. The higher V results in a smaller IMF SA, and this effect is more pronounced near Earth and Mars but less noticeable near Jupiter and Saturn. Our statistical survey provides a reference for the upstream solar wind conditions at these planets, benefiting solar wind studies and planetary space environment research.