Astrophysics and Space Science最新文献

{"title":"Comparative evaluation of neural and physics-based models for forecasting ionospheric Total Electron Content at Low and Mid-latitude Stations during maximum and minimum phases of Solar Cycle 24","authors":"Sunil Kumar Chaurasiya,&nbsp;Kalpana Patel,&nbsp;Abhay Kumar Singh","doi":"10.1007/s10509-026-04591-3","DOIUrl":"10.1007/s10509-026-04591-3","url":null,"abstract":"<div><p>Forecasting ionospheric Total Electron Content (TEC) remains a challenging task for space weather applications due to strong variability across latitudes and solar cycle phases. This study presents a comparative analysis of neural network models, namely Long Short-Term Memory (LSTM) and Backpropagation (BP), and physics-based models, including the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) and NeQuick. The evaluation is performed at three GPS stations: Novosibirsk (mid-latitude), Varanasi (low-latitude), and Port Blair (equatorial latitude), during the solar maximum year of 2014 and the solar minimum year of 2018 during Solar Cycle 24. The results reveal station- and solar cycle phase-dependent variations in model performance. In Novosibirsk, LSTM consistently achieved the highest correlation (R ≈ 0.85) and the lowest RMSE, particularly during the solar maximum phase, successfully capturing the variability of storm-time TEC. Varanasi exhibited strong seasonal variability, with neural models maintaining stable performance across both solar phases, whereas physics-based models struggled with equatorial anomaly effects, particularly during the solar minimum. Port Blair showed the largest model differences: LSTM maintained stable performance with reduced error distributions, while NeQuick consistently underestimated TEC, with errors increasing during the solar minimum phase. Seasonal analysis indicates that neural approaches maintain stable performance across all seasons, whereas physics-based models degrade during transitional seasons. At local time 14:00, comparative analysis shows that LSTM exhibits lower RMSE across all stations and phases, achieving a relative accuracy share greater than 40%, while physics-based models remain below 20% accuracy share. All statistical metrics, including the correlation coefficient (R), RMSE, and MRE, were computed by averaging results over stations, seasons, and solar cycle phases under both quiet and disturbed conditions. This station- and phase-resolved study demonstrates the effectiveness of deep learning architectures in ionospheric forecasting. The study enhances TEC prediction by demonstrating improved performance across diverse latitudinal regimes and solar cycle phases, providing comparative insights for space-weather forecasting.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraints on dark matter in neutron stars from recent observations and mass correlation analysis","authors":"Jing Fu Hu,&nbsp;Hang Lu","doi":"10.1007/s10509-026-04588-y","DOIUrl":"10.1007/s10509-026-04588-y","url":null,"abstract":"<div><p>Dark matter admixed neutron stars (DANSs) provide a unique laboratory for probing fundamental dark matter (DM) properties and offer explanations for recent NICER and LIGO/Virgo observations. Accurately constraining their internal DM content is essential. In this work, we construct equations of state for DANS matter by combining twelve covariant density functional nuclear models with a self-interacting bosonic DM model. Solving the two-fluid Tolman-Oppenheimer-Volkoff equations, we systematically examine DM effects on neutron star properties and employ the latest observational constraints to determine the maximum DM mass fraction <span>(f_{chi }^{mathrm{max}})</span> for each nuclear model. Our analysis reveals a robust linear correlation between <span>(f_{chi }^{mathrm{max}})</span> and the maximum mass of pure neutron stars <span>(M_{mathrm{NS}}^{mathrm{max}})</span>. Using this correlation together with the constrained distribution <span>(P(M_{text{NS}}^{max } mid text{EM}))</span>, we derive the probability distribution function for the maximum DM mass in DANSs, <span>(P(M_{chi }^{max } mid text{EM}))</span>. At the 68% confidence level, we obtain <span>(M_{chi }^{mathrm{max}}=0.157^{+0.059}_{-0.040} M{odot })</span>. This quantitative constraint provides a critical prior for interpreting potential DANS signatures, including anomalous tidal deformabilities and distinctive gravitational-wave signals.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining dark energy dynamics in curved spacetime with current observations","authors":"D. Revanth Kumar,&nbsp;Santosh Kumar Yadav","doi":"10.1007/s10509-026-04585-1","DOIUrl":"10.1007/s10509-026-04585-1","url":null,"abstract":"<div><p>We investigate a dark energy (DE) equation of state (EoS) parametrization in a curved spacetime using current observations. We constrain the model parameters by using observational Hubble data from Cosmic Chronometer (CC), Pantheon Plus SH0ES (PPS), and DESI BAO DR2, along with their reconstructed datasets using an Artificial Neural Network (ANN). The parameter <span>(alpha )</span> is constrained as <span>(alpha approx 0.35 (approx 0.56))</span> from original (reconstructed) data. This means reconstruction pushes the model toward a significant deviation from the standard <span>(Lambda )</span>CDM framework. We find that the curvature parameter <span>(Omega _{k0} = 0.068 pm 0.029)</span> at 68% CL with original data, suggests a slightly open universe, whereas with the reconstruction method, <span>(Omega _{k0} = -0.131 pm 0.032)</span> at 68% CL suggests a closed universe. This shift in the mean value indicates that the reconstruction method is highly sensitive to curvature. We perform statistical model comparison criteria, namely, AIC and BIC to assess the reliability of our framework.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of the best dark matter profile for the Milky Way with Gaia DR3 using Bayesian model comparison","authors":"Aryan Singh,&nbsp;Shantanu Desai","doi":"10.1007/s10509-026-04589-x","DOIUrl":"10.1007/s10509-026-04589-x","url":null,"abstract":"<div><p>We carry out a Bayesian model comparison analysis to determine the dark matter model that best describes the Milky Way rotation curve, using four recent compilations of rotation-curve velocities with the Gaia data. We compare these data using three different baryonic models along with seven different dark matter models. Within the adopted modeling framework and Gaia-based rotation curve datasets, we find that the Einasto profile provides the preferred phenomenological fit compared to the NFW profile across most combinations of datasets and baryonic models. We also find that the cored dark profiles are preferred over the (cuspy) NFW profile. We also test MOND using three different interpolating functions and find that, within the implementations considered, the models provide poorer fits than the preferred dark matter profiles. Finally, among the different baryonic models considered, none is decisively favored over the others.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Equilibrium and stability in Robe’s restricted problem with a line segment and modified potential","authors":"Sumit Kumar,&nbsp;Bhavneet Kaur,&nbsp;Mukesh Kumar,&nbsp;Nitesh Kumar","doi":"10.1007/s10509-026-04584-2","DOIUrl":"10.1007/s10509-026-04584-2","url":null,"abstract":"<div><p>In mathematics, particularly in dynamical systems theory, equilibrium points and their stability are of critical importance, as they represent the steady-state solutions of a system. This study examines the equilibrium points and their stability in a modified formulation of a well known dynamical system: the Robe’s problem. Unlike the original Robe problem where the primary <span>(m_{2})</span> is treated as a point mass, we have modeled <span>(m_{2})</span> as a line segment. The line segment is assumed to produce modified Newtonian potential instead of classical Newtonian potential. The introduction of a modified Newtonian potential leads to substantial changes in the system’s dynamics when compared to the classical Robe’s problem with line segment. Using analytical techniques, we show that the modified system admits only a single collinear equilibrium point, in contrast to the classical case, which allows infinite equilibrium points, including non-collinear (degenerate equilibrium set) and out-of-plane equilibrium points. A linear stability analysis of this equilibrium point indicates marginal stability, with all eigenvalues lying purely on the imaginary axis. This suggests that small perturbations neither grow exponentially nor decay, indicating the absence of inherent damping or restoring mechanisms. Overall, the findings highlight how departures from point-mass assumptions and classical Newtonian potentials can significantly influence the qualitative dynamics of Robe’s restricted three-body system by breaking the degeneracy of equilibrium configuration.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147938663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Equilibrium states of a dual satellite’s system in the regular polygon problem of ((N + 2)) bodies where the central primary creates a Manev-like quasi-homogeneous potential","authors":"Maria N. Croustalloudi,&nbsp;Tilemahos J. Kalvouridis","doi":"10.1007/s10509-026-04581-5","DOIUrl":"10.1007/s10509-026-04581-5","url":null,"abstract":"<div><p>In this work we investigate the equilibrium states of a pair of two small bodies, natural or artificial, that remain very close to each other, undergo a weak interaction and move in the field created by a formation of <span>(N=nu +1)</span> large bodies, <span>(nu )</span> of which have equal masses and are located at the vertices of an imaginary regular <span>(nu )</span>-gon while the <span>(N)</span>th body with a different mass is located at the center of mass of the system. We consider that forces acting on the small bodies by all large primaries are produced by the classical Newtonian gravitational potential of these bodies. However, the potential produced by the central primary is characterized by an additional Manev-type inverse square corrective term. This term may play the role of a normalizing factor of the Universal Law of Gravitation in cases where the central primary is a non-spherical body (oblate or prolate spheroid) or a strong source of radiation. By assuming that the primary bodies are in relative equilibrium, we give the equations of motion of the pair of small bodies, in a synodic coordinate system rigidly attached to the primaries. We numerically investigate the equilibrium states and study their stability. A part of this work is dedicated to the parametric variation of two characteristic quantities of the small bodies, that is the distance <span>(rho )</span> between them and their Jacobian constant <span>(C_{p})</span> at an equilibrium state.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147938593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Observational signatures of scalar field dynamics in modified (f(Q, L_{m})) gravity","authors":"Amit Samaddar,&nbsp;S. Surendra Singh","doi":"10.1007/s10509-026-04580-6","DOIUrl":"10.1007/s10509-026-04580-6","url":null,"abstract":"<div><p>We investigate the cosmological implications of a tanh-parametrized scalar field model in the framework of modified <span>(f(Q, L_{m}))</span> gravity by adopting the form <span>(f(Q, L_{m})=beta Q+delta L_{m})</span> along with a scalar field energy density <span>(rho _{phi }= rho _{c0} tanh (A + Bz))</span>. Using MCMC methods and combining 31 cosmic chronometer data points, 15 BAO, DESI DR2 BAO and 1701 Pantheon+ samples, we constrain the model parameters and obtain <span>(H_{0}=74.284^{+4.155}_{-4.275})</span>, <span>(Omega _{m0}=0.326^{+0.093}_{-0.072})</span> and <span>(B=-0.001^{+0.030}_{-0.030})</span>. The model predicts a transition redshift <span>(z_{tr}=0.5914)</span> and a present deceleration parameter <span>(q_{0}=-0.5167)</span>, consistent with a Universe transitioning from deceleration to acceleration. We further analyze the evolution of the EoS parameter, density components and statefinder diagnostics in which all parameters show asymptotic convergence to a de Sitter phase. Additionally, we study black hole mass accretion within an effective framework, showing its dependence on the scalar field dynamics governed by the cosmological evolution. This work highlights the compatibility of tanh-scalar field forms with <span>(f(Q, L_{m}))</span> gravity in describing cosmic acceleration and gravitational phenomena.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147938840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A GNSS-based index IROTI analysis for distinguishability of TIDs and EPBs over low-latitude Indian region during geomagnetic storms","authors":"Srilatha Talluri,&nbsp;M. Ravi Kumar,&nbsp;Swapna Raghunath,&nbsp;Devanaboyina Venkata Ratnam","doi":"10.1007/s10509-026-04579-z","DOIUrl":"10.1007/s10509-026-04579-z","url":null,"abstract":"&lt;div&gt;&lt;p&gt;GNSS-based communication systems, positioning accuracy, and space weather conditions are significantly influenced by Equatorial Plasma Bubbles (EPBs) and Traveling Ionospheric Disturbances (TIDs), especially in equatorial and low latitude regions such as India. The commonly used metric for tracing EPBs is the Rate of Total Electron Content Index (ROTI). Ground-based GNSS receivers are vital tools for detecting TIDs and EPBs by monitoring rapid variations in Total Electron Content (TEC). To accurately track irregularities, these receivers offer high-resolution temporal and spatial data in both quiet and geomagnetic conditions. In this study, the ionospheric disturbance index, namely the time-integrated ROTI (IROTI), is implemented to detect and classify both TIDs and EPBs, with a primary focus on its regional validation and application over the Indian sector. Seven geomagnetic storms which occurred on 17 March 2015, 23 April 2023, 10 May 2024, 8 September 2017, 23 June 2015, 19 April 2024, 11 October 2024 and eight quiet days on 21 May 2020, 7 July 2015, 15 September 2018, 28 January 2011, 1 January 2024, 10 April 2024, 12 June 2024, 25 October 2024 are counted for analysis using GNSS TEC data from Indian stations. IROTI Index on 17 March 2015 geomagnetic storm indicating both EPBs and TIDs with a higher spatial spread and clear temporal separation, with IROTI (EPB) values typically ranging from 8 to 40 TECU&lt;sup&gt;2&lt;/sup&gt; and IROTI (TID) values from 1.8 to 4.25 TECU&lt;sup&gt;2&lt;/sup&gt;. The storm that occurred on 23 April 2023 exhibited IROTI (TID) activity between 0.64 and 3.1 TECU&lt;sup&gt;2&lt;/sup&gt; and IROTI (EPB) activity that typically ranged between 8 and 38.5 TECU&lt;sup&gt;2&lt;/sup&gt;. During an extreme geomagnetic storm on 10 May 2024, IROTI values ranged between 8 and 60 TECU&lt;sup&gt;2&lt;/sup&gt; during EPBs. On 8 September 2017, a severe storm produced IROTI (TID) values between 0.3 and 2.12 TECU&lt;sup&gt;2&lt;/sup&gt; and IROTI (EPB) values ranging from 8 to 14 TECU&lt;sup&gt;2&lt;/sup&gt;. The storm event observed on 23 June 2015 exhibited IROTI (TID) activity ranging from 0.2 to 4 TECU&lt;sup&gt;2&lt;/sup&gt;. On 19 April 2024, a moderate geomagnetic storm, IROTI values were responsive between 8 and 40 TECU&lt;sup&gt;2&lt;/sup&gt; during EPBs, even on 11 October 2024, only EPBs were observed. Medium-scale TIDs (MSTIDs) were observed on eight quiet days mentioned above during post-sunset hours from 14:00–24:00 UT with magnitudes ranging from 0.2 to 2 TECU&lt;sup&gt;2&lt;/sup&gt;. Statistical Analysis of ROTI and IROTI during TIDs periods is investigated for 7 geomagnetic storms and 8 quiet days, and a 92.3% detection efficiency for TIDs is found using IROTI, compared to only 7.69% using ROTI over the Indian region. The experimental findings demonstrate that IROTI performs noticeably better than conventional techniques such as ROTI across a range of geomagnetic conditions. The suggested index clearly distinguished between EPBs and TIDs and detected both. This approach offers a significant advancement for space weather mo","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147938842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonal insolation variability on early Venus: implications for energy budget","authors":"Stephen R. Kane","doi":"10.1007/s10509-026-04586-0","DOIUrl":"10.1007/s10509-026-04586-0","url":null,"abstract":"<div><p>Venus and Earth are similar in bulk properties yet followed dramatically different climatic trajectories. Reconstructing the climate evolution of Venus requires understanding how variations in rotation rate, obliquity, orbital eccentricity, and solar luminosity shaped the spatial and temporal distribution of incident energy and the atmospheric response. Here we present latitude-orbital phase maps of incident solar flux for Venus at the present epoch and at an age of 0.5 Gyr, when the Sun was fainter and Venus may have occupied a different dynamical state. We explore endmember rotation regimes (slow-rotator and fast-rotator), moderate obliquity (10°), and elevated eccentricity (<span>(e = 0.15)</span>–0.30), motivated by dynamical studies that quantify plausible limits. To translate the flux maps into climate-relevant quantities, we apply an idealized atmospheric energy-balance framework, including both global (0-D) and latitude-dependent (1-D) formulations calibrated to modern Venus. This framework is used to define a radiative relaxation timescale that links forcing variability to expected thermal response. This approach provides a link between orbital forcing and surface energy balance, allowing an assessment of seasonal and orbital variability relative to Venus’s extreme greenhouse state. Our results show that, while early Venus could experience substantial redistribution of insolation across latitude and orbital phase, the orbit-averaged incident flux varies only modestly across the explored parameter space and the dominant control on surface temperature remains atmospheric opacity. Insolation variations therefore act primarily as modulators rather than primary drivers of climate state, with their climatic expression governed by the competition between the forcing timescale and the radiative adjustment time. The provided insolation maps and response diagnostics may serve as boundary conditions for future 3-D climate simulations that investigate the early history of Venus, including regimes in which temperate surface conditions may have been sustained.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10509-026-04586-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147938244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radiation belt dynamics during the shortest and longest HILDCAA events: Van Allen probes observations","authors":"Ayushi Nema,&nbsp;Ankush Bhaskar,&nbsp;Kamlesh N. Pathak,&nbsp;Abhirup Datta","doi":"10.1007/s10509-026-04583-3","DOIUrl":"10.1007/s10509-026-04583-3","url":null,"abstract":"<div><p>High-intensity long-duration continuous auroral electrojet activity (HILDCAA) is a characteristic phenomenon of long-lasting geomagnetic disturbance in the Earth’s magnetosphere. They have been related to increased relativistic electron fluxes in the Earth’s magnetosphere, but the exact mechanisms are not fully established. By scanning Van Allen Probes data from 2014 to 2019, this study investigates two distinct HILDCAA events: one short and one long duration. Both events result in increases in electron flux across several energy channels, according to spectral and temporal investigations. The longer event, however, produces a sharper, stronger, and longer-lasting enhancement in flux, whereas the shorter event exhibits a weaker and more fleeting reaction. Sustained solar wind energy input that enables effective particle acceleration is maintained during extended HILDCAA intervals, accompanied by prolonged geomagnetic activity and repeated substorm injections. In comparison to the shorter event, this one likewise shows a stronger energization of electrons to higher energies. Analysis of plasma waves reveals that the observed flux enhancements are due to increased chorus wave activity and increased ultra-low frequency (ULF) wave activity during the long-duration event. The phase space density (PSD) profiles show local acceleration at L^* = 4.5 to 5.0, while PSD shifts outward and decreases at higher energies. Spectral steepening and greater PSD peaks suggest that the longer HILDCAA event generally enables more efficient and sustained electron acceleration. These findings highlight, that event duration is a significant controlling parameter of outer radiation belt electron dynamics, modulating the efficiency of local acceleration, spectral evolution, and wave-particle interaction. While the two events not exactly identical and differ in solar wind driving conditions, the results are consistent with past statistical studies and indicate need of modeling studies to rigorously separate these effects. The necessity of including long-term geomagnetic disturbances and their duration in magnetospheric specifically radiation belt simulations is strongly supported by these observations.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"371 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147937851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}