Longitudinal structuring of the ionosphere reflects the coupled neutral and electrodynamic processes that shape regional plasma transport and space weather variability; however, its behavior at low-midlatitudes remains incompletely understood. Here we investigate longitudinal variations in ionospheric total electron content (TEC) over South America during the 2020-2021 solar minimum using ground-based Global Navigation Satellite System observations, COSMIC-2 radio occultation data, and ICON in situ measurements. We identify a previously unreported diurnal east-west differential structure extending across low- and midlatitudes during local summer (November-February). The observed pattern exhibits a three-phase evolution: enhanced daytime TEC in the western sector before local noon, a post-noon to sunset reversal with higher TEC in the eastern sector, and a subsequent return to western dominance. Simulations from the Horizontal Wind Model 14 reproduce the TEC structure near noon and after sunset but show opposite behavior in the early morning, indicating that neutral wind forcing alone cannot account for the observations. Multi-instrument analysis further reveals that longitudinal gradients in electric fields and field-aligned diffusion contribute significantly to the TEC asymmetry. These results demonstrate that low-midlatitude longitudinal TEC variations over South America arise from the interplay of multiple physical mechanisms and exhibit substantially greater complexity than their midlatitude counterparts, highlighting the need to incorporate coupled neutral and electrodynamic processes in regional ionospheric modeling and space weather prediction.

Using the multiple ground-based/space-based observations, an abnormal response of ionospheric irregularities in the eastern Pacific region during the recovery phase of the great magnetic storm on 24 April 2023 was analyzed. The ground-based GPS observations exhibited ionospheric irregularities occurred from night to day, lasting for over ten hours, with the longest exceeding 14 h, especially near the magnetic equatorial region. SWARM satellites detected significant plasma bubble/disturbance structures near sunset and in the morning when crossing the low latitude and equatorial region from the western Americas to the eastern Pacific. The satellites (C2E1-C2E5) of COSMIC-2 detected the strong ionospheric bubbles and their quasi periodic structures when crossing the low latitude region from the eastern Pacific to the western Americas (-180 degrees to-60 degrees), which occurred from sunset to daytime, lasting up to 10-14 h. The enhanced eastward electric field and the seed disturbance maybe main factors for the occurrence of ionospheric irregularities in the eastern Pacific region during the recovery phase of magnetic storm on 24th. (c) 2026 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Based on the vertical Total Electron Content (TEC) data observed by the Global Navigation Satellite System in the northern hemisphere, a large area of low plasma density during summer at high latitudes, termed decreased TEC region, was investigated statistically between 2014 and 2024. Compared with the classical depleted structures that usually occur in the nighttime F region at high latitudes during winter, decreased TEC region is usually found in the sunlit polar cap ionosphere during summer. The decreased TEC region is predominantly located in regions above 70° magnetic latitude for moderate and high solar activity. The lower‐TEC region is biased towards the dawn and midnight sectors. Along the 18:25–06:25 Magnetic Local Time meridian, the depth of the decreased TEC region reached 7.6TECu in 2014. The decreased TEC region is deeper for higher Kp (Kp > 2) than for low Kp (Kp ≤ 2).

During solar storms, the polar cusp often exhibits electron populations with distinct velocity distributions, which may be associated with the two-stream instability. This study reveals the evolution of the two-stream instability associated with electron velocities and the interaction between the growth phase of the two-stream instability and the electrostatic solitary waves (ESWs). The results from particle-in-cell (PIC) simulations are compared with satellite observational data and computational outcomes. The potential risks associated with two-stream instability, including surface charge accumulation and communication system interference on spacecraft, are also explored. The findings show that, in the high-latitude polar cusp region, the interaction between the solar wind plasma propagating along magnetic field lines and the upward-moving ionospheric plasma could drive two-stream instability, leading to the formation of electron hole structures in phase space and triggering a bipolar distribution of ESWs. When the spatial magnetic field and wave vector meet specific conditions, the enhanced electron cyclotron motion could suppress the formation of two-stream instability and electron hole structures, leading to a reduction in the amplitude of the ESWs. The results offer valuable insights for a deeper understanding of the impact of solar storms on the polar cusp environment, as well as for monitoring electromagnetic environment and ensuring the stable operation of spacecraft.

The ionospheric irregularities in the East Asian sector mainly occur in the equinox months, but they also occur occasionally in the solstice months, that is, the unseasonal ionospheric irregularities. The study of the morphology and mechanism of this kind of unseasonal irregularities has been a hot topic in recent years. Using the rate of the TEC index (ROTI) map derived from the observation of multiple GNSS receiver network in China, combined with observations from four ionosondes located in Hainan and Guangzhou, the ionospheric irregularities that occurred in China’s low-latitude region during the geomagnetic quiet period on July 5 and 17, 2013 are studied, and their spatiotemporal evolution during these two events is provided. Unlike the irregularities in equinox months, both concerned events occurred near midnight, and when the irregularities appear above the ionosonde station, the range spread F emerges in the ionograms. Comparatively, the irregularities on July 5 mainly appear before midnight, while the irregularities on July 17 were present both before and after midnight, and the intensity and range of the irregularities on July 5 are greater than those on July 17. The irregularities can be identified as two discrete patches located on the east and west sides in both events. They initially appeared at lower latitudes and gradually drifted northeastward, roughly drifting from the region of 15°N and 105°E to the region of 25°N and 125°E. The eastward drift velocity on July 5 and 17 is estimated to be about 32 and 39 m/s, respectively. In addition, it is noted that the irregularities exhibit a little southward drifting in the final evolving stage in both events, which may be related to the meridional wind in the thermosphere. During and before the irregularities, the increase of the ionospheric foF2 and TEC is observed, but the pre-sunset reversal enhancement or the increase of hmF2 that is favorable for the development of irregularities is not observed. Considering the relatively quiet geomagnetic conditions during these two events, the reason for these two irregularities cannot be determined.

In the context of global warming, the accurate prediction of Arctic Sea Ice Concentration (SIC) is crucial for the development of Arctic shipping routes. We have therefore constructed a lightweight, non-recursive spatio-temporal prediction model, the Spatio-Temporal Decomposition Network (STDNet), to predict the daily SIC in the Arctic. The model is based on the Seasonal and Trend decomposition using Loess (STL) decomposition idea to decompose the model into trend and seasonal components. In addition, we have designed the Global Sparse Attention Module (GSAM) to help the model extract global information. STDNet not only extracts seasonal signals and trend information with periodical correspondence from the data but also obtains the spatio-temporal dependence features in the data. The experimental methodology involves predicting the next 10 days based on the first 10 days of data. The prediction results provided the following metrics for the 10-day forecast of STDNet: Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), and coefficient of determination of 1.988%, 3.541%, 5.843%, and 0.979, respectively. The average Binary Accuracy (BACC) at the beginning of September for the period 2018–2022 reached 93.85%. The proposed STDNet model outperforms and is lighter than existing deep-learning-based SIC prediction models.

In this study, we offer an extensive examination of the F-region ionospheric disturbances during the May 2024 superstorm, focusing primarily on the middle-low latitude regions of East Asia. Our analysis is grounded in a wealth of data sources including Total Electron Content (TEC), ionospheric parameters NmF2 and hmF2, Electron Density Profile (EDP) retrieved from Radio Occultation (RO) data, and & sum;[O]/[N2] from the Global Ultraviolet Imager (GUVI), among others, complemented by model simulations. The observed negative ionospheric storm effect, characterized by a significant and long-lasting reduction in electron density across the entire China, commenced immediately following the sudden storm commencement (SSC) on 10 May and continued through the main and early recovery phase of the storm on 11 May. On 11-12 May, positive ionospheric storm impacts were initially observed in a restricted geographical area from the post-midnight to sunrise, first manifesting over the eastern regions of China and then shifting to the central regions. Subsequently, a pronounced negative storm effect persisted throughout the later stages of recovery phase. In contrast, the western regions of China experienced a positive storm effect on 12 May followed by a comparatively mild negative storm phase. This persistent extensive zonal gradient in electron density across the East Asian region resembles the scenarios depicted in prior superstorms attributed to the thermospheric circulation patterns. The disparity in the ionospheric response from east to west in this area is probably a common feature during superstorms, potentially resulting from an arch-shaped structure of elevated & sum;[O]/[N2]. The superstorm in May 2024 led to a significant and persistent decrease in electron density at middle-low latitude over Eastern China Positive ionospheric effects spread from post-midnight eastern China to central China, with western China seeing a weaker positive storm The disparity in ionospheric response from east to west mainly arose from an arch-shaped structure of elevated & sum;[O]/[N2]

An intelligent high-definition and short-term prediction of ionograms with/without Spread-F for the observation at Hainan (19.5 degrees N, 109.1 degrees E, magnetic 11 degrees N) is presented in this paper, which comprises a spatio-temporal ConvGRU network and a super-resolution EDSR network. Our prediction is based on spatio-temporal features in the ionogram graph only. There are 469,227 ionograms classified into 5 categories, that is, frequency/range/mix/strong range/no Spread F, over a solar cycle (14 years) labeled manually by the research group, and we process these ionograms into two data sets for training the two networks mentioned above. A series of comprehensive experiments have been designed and conducted to determine the optimal super-parameters. Our method inputs 8 consecutive authentic ionograms (lasting 2 hr) and generates the next 2 figures (next 30 min). Remarkably, all predicted figures achieve a high accuracy rate of over 94% in predicting the occurrence of Spread-F. Since the clear trace indicates the ionospheric electron density background and the Spread-F indicates disturbances/irregularities, the prediction of both ionograms with/without Spread-F is important to the research and application. There are currently no well-established neural networks specifically designed to predict the extensive information encompassed within ionograms, particularly the intricate characteristics of Spread-F. In this paper, we approach the short-term prediction (next 30 min) of ionograms with/without Spread-F. To achieve this, we employ the ConvGRU network to generate ionograms blurred but still captured the primary spatio-temporal features of various types of Spread-F (FSF/RSF/MSF/SSF) in ionogram sequences, as well as features without Spread-F. Subsequently, we refine these rough images by EDSR network to obtain clear and detailed predictions. Our treatment to blurred prediction figures and our focus on the Spread-F key area are innovative. Through our work, the auto-prediction for ionosonde observation benefits ionosphere research and monitoring. Rather than numerical prediction methods, our prediction is based on spatio-temporal features only Predicting high-definition ionograms by combining ConvGRU and EDSR on the basis of establishing two ionogram data sets Achieving a high accuracy of 94.28% for Spread-F prediction

A series of fusion evaporation reactions induced by the 54Cr17+ Cr 17 + beam have been performed using the gas-filled recoil separator SHANS2. The excitation functions of 54 Cr + 159 Tb and 54 Cr + 165 Ho reactions were measured. The systematics of cross sections for reactions with 40 Ar, 48 Ca, 50 Ti, and 54 Cr projectiles are compiled and discussed. It is suggested that employing the 54 Cr beam holds the potential for synthesizing neutron-deficient actinide nuclei. In addition, we attempted to synthesize undiscovered americium isotopes with 175 Lu( 54 Cr , 3n-4n) n -4 n ) 225 ,226Am , 226 Am reactions. No events were observed originating from 225 Am and 226 Am, and the upper limits were estimated to be 2.1 and 1.7 pb, respectively. The significantly low fission barrier of the compound nucleus 229 Am, which leads to the small survival probability, might be a possible reason for the low cross sections.

In the present work, the Doppler Shift Attenuation method (DSAM) was used to analyze the observed lineshapes of transitions from excited states in 45Sc, populated in the reaction 36Ar + 12C at a beam energy of 145 MeV. The interpretation and comparison of the experimental results have been performed with large-scale shell model calculations, involving different interactions like: GX1A, GX1J, FPD6, KB3 and ZBM2. KB3 and FPD6 (present work) interactions in the negative parity states, and in positive parity states ZBM2 are most pre-eminent in reproducing the results, due to the large configuration space describing strong collective effects. Furthermore, the present work also looks at the details of the shell model helping in improving the understanding for the occupancy of orbitals. The present investigation suggests the observation of stronger collectivity for positive parity states over negative parity states with predicted enhanced collectivity of states in 45Sc nucleus.

Data measured by the Digisonde at the low-latitude station Hainan from 2003 to 2016 are statistically analyzed to specify the diurnal average variations of the bottom-side F region ionospheric plasma velocity vector V. This is the first comprehensive analysis of Digisonde measurements of low latitude F region plasma velocities in the East Asian sector that use a database covering more than one solar cycle. The velocity components V-N (Northward), V-E (Eastward), and V-Z (Upward) are analyzed for two levels of solar flux and two levels of geomagnetic activity, respectively. The diurnal variations of the average V-Z show three positive peaks near the prereversal enhancement (PRE) period, pre-midnight, and before sunrise, respectively, and a prominent valley in the early morning. The averaged V-Z significantly increased with solar flux in the period of PRE during equinoxes, but it was only slightly affected by Kp. The V-E component was westward in daytime and eastward in nighttime. The average eastward V-E increased significantly with solar flux but decreased with Kp, whereas the average westward V-E exhibited only a small variation with solar flux and Kp. The average V-N was almost southward independent of solar flux and Kp. The plasma velocities over the Hainan station were mainly caused by the electric field and neutral wind. Our results show that the features of the vertical and meridional velocities over the Hainan station in the morning are associated with the formation of the equatorial ionization anomaly (EIA).

针对东亚地区地磁低纬度南北半球Vanimo台站(地理2.7°S,141.3°E;地磁11.2°S,146.2°W)和海南台站(地理19.5°N,109.1°E;地磁9.1°N,179.1°W)上空的3个电离层等离子体块与等离子体泡相关联的事件,利用地面台站的电离层测高仪连续观测数据,研究等离子体泡演化期间的电离层虚高变化.结果表明:以往提出的等离子体块出现约2 h之前等离子体垂直漂移速度从向上(东向电场)转为向下(西向电场)的观点,本文的3个事例均与之不符,或者距反转时间很远(约6 h),或者由向下转为向上.在等离子体块形成时间点前的1 h内,均有突发的等离子体堆积的运动趋势,或是下降运动速度突然变慢,或是从下降转为向上运动,或是上升运动速度突然加快.这一堆积现象与等离子体块现象相关性更好,也不仅限于漂移速度从向上转变为向下.

利用海南台站和东南亚地区的多种地基和天基观测手段，对2014年7月28日夜间观测到的东亚低纬F区不规则体事件的时空变化及其物理过程进行分析。结果表明，海南台站观测到了罕见的长时间持续的F区电离层不规则体，不同手段观测到的电离层不规则体存在明显的形态差异。不同台站观测到的电离层不规则体活动存在明显的差异。海南台站经度区南北异常峰附近的TEC起伏活动在日落后至午夜附近明显增强，在午夜后明显减弱。C/NOFS卫星轨迹午夜后逐渐接近于磁赤道，且处于较低高度上，几乎总会观测到弱等离子体扰动/泡的发生，与该区域地基观测的弱电离层不规则体活动存在明显的联系。SWARM卫星在黎明海南台站附近经度区仍观测到较强的赤道异常双峰结构，且西侧异常峰区附近仍存在明显的等离子体密度耗空/泡结构。海南台站西侧磁赤道区附近（中南半岛）强对流活动（MCC）激发的重力波种子扰动对东亚低纬区等离子体泡及准周期结构的产生发挥了重要作用。

The nature of two high-spin bands in Nd-136 built on the two-quasiparticle configuration pi h(11/2)(2), predicted by the triaxial projected shell model as good candidates of transverse wobbling bands, are investigated experimentally. The mixing ratio of one Lambda I = 1 transition connecting the one-phonon and the zero-phonon wobbling bands is established from a high-statistics JuroGam II gamma-ray spectroscopy experiment by using the combined angular correlation and linear polarization method. The resulting wobbling excitation energy and ratios of reduced electromagnetic transition probabilities are in good agreement with results of a new particle-rotor model which rigidly couples the total angular momentum of two quasiparticles to a triaxial core in an orthogonal geometry, confirming thus the transverse wobbling nature of the bands.

利用Cluster四颗卫星的磁场探测数据计算磁尾场向电流并投影到极区电离层，研究其投影位置在南北半球的分布规律，统计过程中去除了强磁暴（磁暴主相Dst＜–100 nT）期间的场向电流事件。结果显示：磁尾场向电流事件在极区投影位置的纬度分布具有明显的南北半球不对称性，北半球为单峰结构，南半球为双峰结构。在北半球投影到较低纬度（＜64°）的场向电流事件数目明显多于南半球，并且所能达到的最低纬度更低；在南半球投影到较高纬度（＞74°）的场向电流事件数目明显多于北半球，并且所能达到的最高纬度更高。地磁平静条件下（|AL|＜100 nT），磁尾场向电流密度随磁地方时（MLT）呈递增趋势，这一结果与低高度卫星在极区对I区场向电流的探测结果符合很好。研究结果表明，磁尾场向电流投影位置的纬度分布呈现出明显的南北不对称性，这与南北半球磁尾场向电流的空间分布以及磁层中磁场结构具有密切关系。

The 19F(p, αγ)16O reaction is of crucial importance for Galactic 19F abundances and CNO cycle loss in first generation Population III stars. Due to its extremely small cross sections, the 19F(p, αγ)16O reaction has not been measured in the low energy part of the Gamow window(70-200 keV). As a day-one campaign, the experiment was performed under the extremely low cosmicray-induced background environment of the China JinPing Underground Laboratory(CJPL), one of the deepest underground laboratories in the world. The γ-ray yields were measured over Ec.m. =72.4–344 keV, covering the full Gamow window for the first time. The direct experimental data will help people to expound the fluorine over-abundances, energy generation, as well as heavy-element nuclosynthesis scenario in asymptotic giant branch (AGB) stars, with the astrophysical model on the firm ground.

The precession of an atomic nucleus can be approximately described as wobbling motion, arising from the coupling of a rotation and a harmonic vibration. Recently, a number of wobbling bands were reported at low spin, which violate the wobbling approximation that can be valid only at high spin. In the present work, we explore the nature of the reported low-spin wobbling bands. Via a new experiment including both angular correlation and linear polarization measurements, we demonstrate that one such band in 187Au is generated by dominant single-particle excitation rather than by the excitation of a wobbling phonon. Assessing the experimental proofs and discussions to assign the reported low-spin wobbling bands, we further point out that the imperfect research paradigm used previously would lead to unreliable identification of low-spin wobbling bands.

The extremely neutron-deficient even-even uranium isotopes( 216,218)U were produced in the complete-fusion reactions induced by impinging Ar-40 and Ca-40 ions on W-180,W-182,W-184 targets. Fusion evaporation residues were separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and subsequently identified using the recoil-alpha-correlation method. The improved ground-state to ground-state alpha-decay properties of( 216,218)U were reported in [Z. Y. Zhang et al., Phys. Rev. Lett. 126, 152502 (2021)]. In this paper, we report on new alpha-decay activities with E-alpha = 10 163(27) keV for 216U and E-alpha = 10 073(16) keV for 218U, which decay from the 8(+) isomeric states of( 216,218)U into the 2(+) states of their daughter nuclei Th-212,Th-214, respectively. The new results extend the systematics of the alpha-decay fine structure for the N = 124 and 126 even-even isotones.

β decay of proton-rich nuclei plays an important role in exploring isospin mixing. The β decay of ^{26}P at the proton drip line is studied using double-sided silicon strip detectors operating in conjunction with high-purity germanium detectors. The T=2 isobaric analog state (IAS) at 13 055 keV and two new high-lying states at 13 380 and 11 912 keV in ^{26}Si are unambiguously identified through β-delayed two-proton emission (β2p). Angular correlations of two protons emitted from ^{26}Si excited states populated by ^{26}P β decay are measured, which suggests that the two protons are emitted mainly sequentially. We report the first observation of a strongly isospin-mixed doublet that deexcites mainly via two-proton decay. The isospin mixing matrix element between the ^{26}Si IAS and the nearby 13 380-keV state is determined to be 130(21) keV, and this result represents the strongest mixing, highest excitation energy, and largest level spacing of a doublet ever observed in β-decay experiments.

The new thorium isotope $^{207}\mathrm{Th}$ has been produced in the $5n$ evaporation channel of the fusion reaction $^{36}\mathrm{Ar}+^{176}\mathrm{Hf}$. It was separated in flight by the gas-filled recoil separator SHANS and identified on the basis of a correlated $\ensuremath{\alpha}$-decay chain. The $\ensuremath{\alpha}$ decay of $^{207}\mathrm{Th}$, measured with an $\ensuremath{\alpha}$-particle energy of 8167(21) keV and a half-life of $9.{7}_{\ensuremath{-}4.4}^{+46.6}$ ms, is assigned to originate from ground state. By combining with existing data, we find that the $\ensuremath{\alpha}$-decay energies of nuclei with $Z>82$ and $N<126$ show a regular and distinct odd-even staggering (OES) rather than the commonly supposed smooth pattern. A theoretical analysis has been performed within relativistic Hartree-Fock-Bogoliubov and large-scale shell-model approaches. It is found that the OES originates from both pairing correlations and blocking of particular orbitals by unpaired nucleons. Of particular importance is that pairing correlations result in the OES not only through the contribution of pairing energy to binding energy, but also by configuration mixing induced by scattering nucleons to orbitals away from Fermi levels.