Journal of Astrophysics and Astronomy最新文献

Local time and longitudinal variability of ionospheric response during extreme geomagnetic events 极端地磁事件期间电离层响应的地方时和纵向变率

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-10-14 DOI: 10.1007/s12036-026-10187-8

CHUKWUMA MOSES ANORUO, ONYINYE G. NWANKWO

{"title":"Local time and longitudinal variability of ionospheric response during extreme geomagnetic events","authors":"CHUKWUMA MOSES ANORUO, ONYINYE G. NWANKWO","doi":"10.1007/s12036-026-10187-8","DOIUrl":"10.1007/s12036-026-10187-8","url":null,"abstract":"<div><p>We analyzed Total Electron Content (TEC) data from 22 GNSS (Global Navigation Satellite System) stations across Africa, Europe, and Asia, spanning equatorial, low, and mid-latitudes, to characterize daytime and nighttime ionospheric storm responses during the geomagnetic events of February 2014 and March 2015. Using a 5-min interval TEC dataset, we employed the threshold |rTEC ≤−30| or |rTEC ≥ 30| to identify positive and negative storm phases relative to a quiet-time defined by the median of the 10 quietest days. To investigate the underlying drivers of these phases, we examined variations in the ΔH-component from collocated magnetometers and evaluated spatial gradients to assess local time evolution and longitudinal variability. Our results show that ionospheric electrodynamics during storms are more strongly controlled by local time and geomagnetic longitude than by storm intensity, although storm strength still modulates the magnitude and spatial extent of the response. Notably, 18.97% of positive phases occur during the daytime compared to 10.94% at night, underscoring the critical role of local time in modulating TEC variability.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149189262","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}

引用次数: 0

Observations of the 21 cm Hi line from the milky way galaxy using pyramidal horn radio telescope 用金字塔角射电望远镜观测银河系21厘米Hi线

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-10-13 DOI: 10.1007/s12036-026-10198-5

Kaustav Bhattacharjee, Himanshu Grover, P Arumugam

引用次数: 0

Energetic particle acceleration and transport: Interplanetary coronal mass ejections and shocks 高能粒子加速和传输：行星际日冕物质抛射和冲击

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-10-13 DOI: 10.1007/s12036-026-10186-9

Olga E. Malandraki, Christina M. S. Cohen, Joe Giacalone, Leng Ying Khoo, Domenico Trotta, Laura Rodríguez-García, Athanasios Kouloumvakos, Zheyi Ding, Yuncong Li, Alexander Kollhoff, John G. Mitchell, David J. Mccomas, Nathan A. Schwadron, Javier Rodríguez-Pacheco, Robert F. Wimmer-Schweingruber, George C. Ho, Glenn Mason, Michalis Karavolos, Jingnan Guo

{"title":"Energetic particle acceleration and transport: Interplanetary coronal mass ejections and shocks","authors":"Olga E. Malandraki, Christina M. S. Cohen, Joe Giacalone, Leng Ying Khoo, Domenico Trotta, Laura Rodríguez-García, Athanasios Kouloumvakos, Zheyi Ding, Yuncong Li, Alexander Kollhoff, John G. Mitchell, David J. Mccomas, Nathan A. Schwadron, Javier Rodríguez-Pacheco, Robert F. Wimmer-Schweingruber, George C. Ho, Glenn Mason, Michalis Karavolos, Jingnan Guo","doi":"10.1007/s12036-026-10186-9","DOIUrl":"10.1007/s12036-026-10186-9","url":null,"abstract":"<div><p>Solar Energetic Particles from suprathermal (few keV) up to relativistic (few GeV) energies constitute an important contributor to the characterization of the space environment. Emitted from the Sun they are associated with solar flares and shock waves driven by Coronal Mass Ejections. This review presents important recent results of the study of Interplanetary CMEs and shocks in relation to energetic particle acceleration and transport, taking advantage of multi-point, multi-instrument observations available by a fleet of spacecraft in the heliosphere. In particular, the Solar Orbiter and Parker Solar Probe pioneering missions providing unprecedented measurements of energetic particles in the near-Sun environment offer promising insights into several unresolved questions particularly regarding the mechanisms responsible for the acceleration and transport of energetic particles in the heliosphere and their relative contributions.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149189207","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}

引用次数: 0

Anomalous scattering of pulsars towards the Gum Nebula 脉冲星对树胶星云的反常散射

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-10-13 DOI: 10.1007/s12036-026-10189-6

M. A. Krishnakumar, Bhal Chandra Joshi, P K Manoharan

引用次数: 0

Generalized Fluctuation Theory of Galaxy Clustering With Continuous Mass Spectra 具有连续质谱的星系群集的广义涨落理论

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-09-30 DOI: 10.1007/s12036-026-10192-x

M. S. Khan, Owais Farooq, Raja Nisar Ali

{"title":"Generalized Fluctuation Theory of Galaxy Clustering With Continuous Mass Spectra","authors":"M. S. Khan, Owais Farooq, Raja Nisar Ali","doi":"10.1007/s12036-026-10192-x","DOIUrl":"10.1007/s12036-026-10192-x","url":null,"abstract":"<div><p>We develop a continuum counts-in-cells fluctuation theory for gravitational clustering in galaxy populations described by a continuous comoving mass function <span>(phi (m,z))</span> within the quasi-equilibrium grand-canonical framework. Starting from the equal-mass and two-species fluctuation sectors, we construct a finite-resolution mass-bin representation, pass to the continuum limit and derive closed expressions for the internal energy, the pressure, and the first four count cumulants in the strict total-count sector. The latter is then rewritten in an intrinsic normalization based on the mean mass <span>(bar{m} = M_1/M_0)</span>, so that the observable hierarchy depends only on the mass function, the clustering parameter, and the thermodynamic control variables. The continuum construction recovers the equal-mass formulas exactly and reproduces the discrete two-species relations in the corresponding singular limit. In the weak-clustering regime, the leading spectral corrections are controlled by the moments <span>(M_3)</span>, <span>(M_6)</span>, and <span>(M_9)</span>. Within the strict total-count criticality condition, the compressibility denominator is pinned to <span>(D_c=1/2)</span>, so the Fano factor takes the fixed value <span>(F_c=2)</span> as an algebraic identity that follows directly from the criticality condition, whereas the higher reduced cumulants preserve explicit dependence on the mass spectrum through the response hierarchy <span>(A_r)</span>. A truncated Schechter specialization for threshold-selected catalogs then makes the physical content explicit: raising the lower mass threshold lowers the critical clustering parameter while increasing the variance-, skewness-, and kurtosis-level responses of the counts-in-cells distribution. The resulting framework furnishes an analytical interface between quasi-equilibrium gravitational clustering theory and finite-resolution mass-selected one-point observables for realistic galaxy populations.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149133266","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}

引用次数: 0

Metallicity dependence of the M-dwarf flare-frequency-distribution slope at fixed mass-based Rossby number across the fully-convective transition 全对流跃迁中固定质量罗斯比数下m -矮耀斑频率分布斜率的金属丰度依赖性

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-09-28 DOI: 10.1007/s12036-026-10191-y

Edison Yang

{"title":"Metallicity dependence of the M-dwarf flare-frequency-distribution slope at fixed mass-based Rossby number across the fully-convective transition","authors":"Edison Yang","doi":"10.1007/s12036-026-10191-y","DOIUrl":"10.1007/s12036-026-10191-y","url":null,"abstract":"<div><p>We measure the cumulative flare-frequency-distribution slope <span>(alpha )</span> as a function of metallicity at fixed mass-based Rossby number across the M3.5/M4 fully-convective transition. From 19,099 SDSS-V DR19 BOSS M dwarfs cross-matched with TESS light curves, we detect flares with a convolutional-neural-network ensemble and fit per-cell <span>(alpha )</span> with a doubly-truncated Pareto. In fully-convective M dwarfs (<span>(M_star le 0.35)</span> M<span>(_odot )</span>, <span>(0.13 le textrm{Ro} < 0.45)</span>), <span>(alpha )</span> increases with metallicity. The robust result is the sign of this ordering: <span>(alpha )</span> is higher in the metal-rich bin by <span>(Delta alpha = +0.23)</span>, independent of the bin centres. A star-level bootstrap is positive in 99.4% of resamples (about <span>(2.5sigma )</span>; the <span>(95%)</span> interval excludes zero), and an independent mass-perturbation Monte Carlo in 94% (<span>(1.6sigma )</span>). The magnitude is systematic-dominated: we adopt the mass-marginalised <span>(+0.13^{+0.07}_{-0.08})</span> dex<span>(^{-1})</span> (the fixed-boundary <span>(+0.26 pm 0.03)</span> is statistical only), and a physical per-dex value awaits better metallicities. The ordering falls to zero as the boundary is raised into the transition zone, which we cannot yet attribute to physics or sample definition.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149133106","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}

引用次数: 0

Performance of the 4-m international liquid mirror telescope tested in two fields at high and low ecliptic and galactic latitudes 4米国际液体反射镜望远镜在黄道高低纬度和银河纬度两个区域进行了性能测试

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-09-27 DOI: 10.1007/s12036-026-10161-4

Sara Filali, Kumar Pranshu, Jean Surdej, Paul Hickson, Kuntal Misra, Bhavya Ailawadhi, Talat Akhunov, Monalisa Dubey, Naveen Dukiya, Brajesh Kumar, Priyanshi Kumari, Vibhore Negi, Anna Pospieszalska-Surdej

{"title":"Performance of the 4-m international liquid mirror telescope tested in two fields at high and low ecliptic and galactic latitudes","authors":"Sara Filali, Kumar Pranshu, Jean Surdej, Paul Hickson, Kuntal Misra, Bhavya Ailawadhi, Talat Akhunov, Monalisa Dubey, Naveen Dukiya, Brajesh Kumar, Priyanshi Kumari, Vibhore Negi, Anna Pospieszalska-Surdej","doi":"10.1007/s12036-026-10161-4","DOIUrl":"10.1007/s12036-026-10161-4","url":null,"abstract":"<div><p>The 4-m International Liquid Mirror Telescope (ILMT) offers a unique opportunity to detect transients in a narrow strip of sky. We explore ILMT’s potential to detect astrometric and photometric transients at various ecliptic and galactic latitudes. We inspected CCD frames observed at both low and high ecliptic and galactic latitudes during the commissioning phase and the November 2023 - May 2024 observation cycle, respectively. We analysed these images using both visual inspection and the ILMT’s transient detection and candidate classification pipeline. In the low ecliptic and galactic latitude field, we detected more than 500 transient candidates. We cross-matched these with the Minor Planet Checker (MPC) database, identifying 504 catalogued asteroids, all with predicted V-magnitudes brighter than 24 mag, representing a total of 152 distinct asteroids. We performed the same steps on the high ecliptic and galactic latitude field, detecting 30 MPC-catalogued asteroids, and one newly discovered photometric transient, named AT 2024fxn. We present the positions, trajectories, and magnitudes of the detected asteroids observed in the SDSS <i>g’</i>, <i>r’</i>, and <i>i’</i> spectral bands and compare results from both fields. We explore the lightcurve of AT 2024fxn, which shows partial compatibility with a supernova (SN) hypothesis, while the data invites further insights.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149133022","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}

引用次数: 0

Habitability study of terrestrial planets: Application to Venus-like worlds 类地行星的可居住性研究：在类金星行星上的应用

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-09-27 DOI: 10.1007/s12036-026-10194-9

Swathi Raviprakash, Madhu Kashyap Jagadeesh, Margarita Safonova, Oleg Kotsyurbenko

{"title":"Habitability study of terrestrial planets: Application to Venus-like worlds","authors":"Swathi Raviprakash, Madhu Kashyap Jagadeesh, Margarita Safonova, Oleg Kotsyurbenko","doi":"10.1007/s12036-026-10194-9","DOIUrl":"10.1007/s12036-026-10194-9","url":null,"abstract":"<div><p>The study of planetary habitability beyond Earth remains central and a challenging project in planetary science. Analysis of large volumes of planetary data from space missions such as CoRoT, Kepler, and JWST is directed ultimately at finding a planet similar to Earth–the Earth’s twin, and answering the question of potential exo-habitability. The Earth Similarity Index (ESI) is a first step in this quest, ranging from 1 (Earth) to 0 (totally dissimilar to Earth). To identify planets that may be habitable to the extreme forms of life, we introduced the Mars Similarity Index (MSI). However, extreme forms of life have also been hypothesized under specific conditions in the upper atmosphere of Venus, motivating comparative habitability studies beyond Earth and Mars. The Venus Similarity Index (VSI) introduced here is defined as the geometric mean of radius, density, escape velocity, and surface temperature, normalized in Venus Units (VU). VSI values range from 0 (complete dissimilarity) to 1 (maximum similarity). The VSI provides a comparative framework for identifying Venus-like planetary environments within exoplanet populations. To explore habitability evolution, we further introduce the Ancient Venus Similarity Index (AVSI) and the Future Earth Similarity Index (FESI) to examine early Venusian conditions relative to ancient Earth and to assess potential future evolutionary pathways for Earth-like planets.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149132518","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}

引用次数: 0

Dark matter halo and albedo effects on equilibrium points and non-linear stability zones 暗物质晕和反照率对平衡点和非线性稳定区的影响

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-09-24 DOI: 10.1007/s12036-026-10167-y

Raj Mal Jat, Ram Kishor

{"title":"Dark matter halo and albedo effects on equilibrium points and non-linear stability zones","authors":"Raj Mal Jat, Ram Kishor","doi":"10.1007/s12036-026-10167-y","DOIUrl":"10.1007/s12036-026-10167-y","url":null,"abstract":"<div><p>This study investigates the non-linear dynamical behavior of small space objects (e.g. asteroids, spacecraft, satellites, comets etc.) under the frame of the restricted three-body problem (RTBP), influenced by a dark matter halo and albedo effect from an oblate secondary. The dark matter halo is characterized by an inner density slope parameter <span>(gamma in [0,,3))</span>, which enables representation of both cored and cuspy halo structures. The incorporation of albedo force introduces additional non-gravitational perturbations that enrich the system’s utility. The equilibria configurations are analyzed and a linear stability test is performed up to third order resonance, consequently stability range is obtained. It is observed that both the dark matter halo and albedo significantly influence the positions of equilibrium points and modify the topology of their stability regions. Again, non-linear stability zone and Poincaré surface of section around a linearly stable equilibrium is estimated using long-term numerical integration based on the fourth order Runge-Kutta method. The obtained results indicate that the halo parameters (<span>(M_h)</span>, <span>(gamma )</span>) enhance stability domains, whereas radiation pressure, albedo, luminosity ratio and oblateness reduce them. Numerical simulations reveal that the non-linear stability zone is highly sensitive to the oblateness coefficient <span>(A_2)</span> and increments in the radiation pressure broadens the librational region, while greater halo concentration or geometric asymmetry constricts it. The study extends the classical RTBP to a more realistic astrophysical regime, providing new insights into the interplay of gravitational, radiative, and halo-induced perturbations in governing orbital stability within halo-dominated galactic systems.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149035040","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}

引用次数: 0

Testing the generalization and domain stability of compact feature representations for photometric supernova classification 用于光度超新星分类的紧凑特征表示的泛化和域稳定性测试

IF 1.5 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2026-09-22 DOI: 10.1007/s12036-026-10184-x

Anurag Garg

{"title":"Testing the generalization and domain stability of compact feature representations for photometric supernova classification","authors":"Anurag Garg","doi":"10.1007/s12036-026-10184-x","DOIUrl":"10.1007/s12036-026-10184-x","url":null,"abstract":"<div><p>Photometric classification of supernovae increasingly requires models that are not only accurate within a single survey, but also stable under changes in cadence, noise properties, filter coverage, and survey domain. In this work, we test the generalization and domain stability of a compact 16-feature representation for Type Ia supernova classification. The feature set consists of physically interpretable light-curve descriptors measuring brightness scale, color structure, variability, and temporal evolution. Using the Supernova Photometric Classification Challenge (SPCC) dataset as the reference domain, we first confirm that the compact XGBoost classifier preserves strong within-survey performance, achieving an F1 score of approximately 0.844 and a PR-AUC of approximately 0.928 on the held-out test set. We then evaluate robustness under alternate classifiers, repeated resampling, synthetic feature perturbations, missing-band proxies, shortened temporal coverage, and cross-survey transfer to PLAsTiCC. The compact representation remains stable under resampling and moderate perturbations, but external transfer reveals a substantially larger limitation. Direct SPCC<span>(rightarrow )</span>PLAsTiCC transfer produces a marked drop in performance, and class-conditional centroid analysis shows that the SPCC and PLAsTiCC Type Ia populations do not occupy the same region of the compact feature space. The cross-survey Ia centroid shift is larger than the Ia/non-Ia separation within either survey, indicating that the transfer gap is caused by feature-space domain shift rather than classifier instability alone. These results show that compact physically interpretable features are robust within a survey and useful for diagnostic analysis, but are not automatically survey-invariant. Cross-survey deployment requires feature-space harmonization, domain adaptation, or restriction to a smaller set of survey-stable features.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149034431","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}

引用次数: 0