Zhijun Zhao

This study systematically examines differential rotation of α- type (unipolar), β- type (bipolar), and βx- type (complex) sunspot groups (SGs) using 1986–2025 RGO/USAF/NOAA data across solar cycles (SCs) 22–25. Methods include daily displacement measurements for rotation rates, outlier removal, binomial fitting for differential rotation profiles, and comparisons across magnetic types, cycles, and hemispheres. Our key findings are as follows: βx- type SGs exhibit the most pronounced differential rotation and significant cycle-dependent variations, with stronger differential rotation in active cycles (22–23) and weaker in less active ones (24–25); α- and β- type SGs show similar stable profiles. A comparison of near-equatorial low-latitude (10°) rotation rates across SCs reveals that both α- and β- type SGs are ordered as follows: SC 25 > SC 24 > SC 23 > SC 22; in contrast, βx- type SGs exhibit a different sequence: SC 25 > SC 23 > SC 22 > SC 24. The rotational rates of βx- type SGs exhibit inconsistent hemispheric dominance across different cycles; the north–south hemispheric differences in rates between α- and β- type SGs are relatively weak.

Using multi-wavelength imaging and spectroscopic observations from the New Vacuum Solar Telescope (NVST), the Chinese Hα Solar Explorer (CHASE), and the Solar Dynamics Observatory (SDO), we investigate a highly twisted magnetic structure associated with a filament eruption in active region (AR) NOAA 13762 during 2024 July 25–26. Initially, several jets were triggered along coronal loops by magnetic flux emergence, resulting in an exchange of loop footpoints toward the emerging negative polarity. Meanwhile, distinct brightenings were observed at the interface between two filament segments, accompanied by photospheric magnetic flux cancellation. Subsequently, the two filament segments merged into a single filament. The merged filament later erupted, exhibiting a highly righthanded twisted magnetic structure, while its threads displayed a left-handed rotational motion. This behavior suggests that the filament interacted with nearby closed magnetic fields, injecting magnetic twist into the surrounding coronal system. The total twist of the magnetic structure during the eruption is estimated to be about 2.59 turns, implying that the original filament possessed an intrinsic twist of approximately 1.59 turns. During the later phase of the eruption, several brightenings and moving bright threads exhibiting right-handed rotational motion or bidirectional propagation were observed, after which the structure evolved into a less twisted configuration. We propose that the magnetic twist was partially transport to the surrounding coronal loop through magnetic reconnection during the twist-transfer stage. The observed brightenings and moving threads are interpreted as signatures of magnetic reconnection occurring between the edge of the highly twisted structure and surrounding coronal loops. These results provide new insight into the transfer of magnetic twist during the interaction between a highly twisted filament and surrounding closed magnetic loops.

Solar coronal rotation exhibits significant complexity, and its relationship with the 11 yr solar cycle remains poorly understood. Using 597 McIntosh synoptic maps (CR1601–CR2197), we construct the temporal evolution of coronal rotation by performing cross-correlation analysis of coronal hole areas between consecutive Carrington rotations. Results show coronal rotation rate decreases from the equator to mid-latitudes (45°–60°), then increases at high latitudes (>60°). Comparison across solar cycles 21–24 reveals that cycle 23 displays the highest equatorial rotation rate and the strongest differential rotation. Equatorial rotation rates in odd-numbered cycles are generally higher than in preceding even-numbered ones. The latitudinally averaged rotation rate reaches a minimum near solar maximum and recovers during the declining phase, likely due to the latitudinal migration of coronal holes. Hemispheric asymmetry analysis shows no significant north–south difference in rotation rates, contrasting sharply with the strong asymmetry in sunspot distributions. Time series analysis of rotational parameters A, B, and C reveals a significant negative correlation between A and B, and a positive correlation between A and C. Singular spectrum analysis identifies prominent 5.6 and 6.9 yr periods in all three, with only C showing a strong 10 yr period.

In the smelting and processing of alloys, the precise control of temperature is highly dependent on non-contact radiation temperature measurement technology, and spectral emissivity is the core parameter that determines the measurement accuracy of this technology. In this study, electromagnetic suspension devices were used to conduct multi-period suspension melting experiments on four alloys. Aiming at the problem that the emissivity is unknown and varies dynamically with time during the phase transition of alloys, an unconstrained algorithm based on spectral wavelength response band differential analysis is proposed, and then the dependence of spectral emissivity on wavelength and temperature of four alloys (304, 316, Inconel 600, and GH3030) is systematically studied. The results show that in the solid state, the emissivity of the alloy increases with the increase in temperature. In the molten state, the correlation between emissivity and temperature is weak. In addition, unlike the monotonous decrease in emissivity of pure metals with wavelength, the emissivity of alloys shows a non-monotonic trend. The comparison of measurement and simulation results verifies the reliability of the emissivity inversion results and shows that the unconstrained algorithm provides an effective new way to accurately obtain the true temperature and emissivity of the alloy.

为了评价积尘对镜面反射特性影响程度并预测积尘环境中镜面反射率的变化趋势，利用时域有限差分法对不同积尘状态下的镜面红外反射率进行仿真计算，基于响应面法构建了反射率多因素影响模型，通过双向反射分布函数测量实验验证了模型准确性。实验结果表明：在1.55 μm~5 μm波长范围，镜面反射率随波长增加而增大，随积尘密度增加而显著下降，随入射角增大而明显降低；积尘密度、波长和入射角对镜面反射率有明显的协同影响，对于50 mg/m²积尘密度，入射角55°时，波长从1.55 μm增加到5 μm时反射率相对增幅为15°时入射角的7.5倍；对于3.6 μm波长，积尘密度为100 mg/m²时，入射角从15°增加到55°时反射率降幅是无尘时的3倍。研究结果为光学系统杂散光分析提供了数据支持，可为反射镜等光学元件清洁维护提供指导。

天空背景辐射是限制红外天文观测灵敏度的重要参数，是红外台址评价的关键指标。为了满足大口径红外望远镜选址需要，提出一种8 μm~12 μm波段便携式天空辐射仪设计方案。根据测量天空辐射0.1%时天空变化需求确定了光学系统性能参数，采用2片透镜组成的光学系统最大限度降低杜瓦制冷的热负载，利用二元面和非球面组合消除工作温度范围内的色差和热离焦，光学系统在不同环境下均达到了衍射极限（艾里斑半径30 μm）。将有限元分析和光学仿真结合，研究不同环境温度下光学元件形变和温度梯度对像差的影响。结果表明：环境温度−60 ℃时像差最大，点列图几何半径大于42 μm，但均方根半径小于20 μm，截止频率处调制传递函数大于0.069 54，接近衍射极限。因此，无需调焦机构及封窗控温，该辐射仪能够满足天空辐射时空变化的测量需求。

• Synchronized observations of sporadic Ni and sporadic Na layers were conducted using a Na-Ni dual-wavelength lidar system. • The seasonal variation of sporadic Ni is similar to that of sporadic Na. • The peak density ratio of sporadic Na to sporadic Ni is approximately 5, which is half the density ratio of the two main layers.

We present a comprehensive analysis of solar photospheric rotation during the ascending phase of solar cycle 25 using Carrington synoptic magnetic maps (December 2019–July 2025) and cross-correlation techniques. By constructing rotational profiles and deriving the coefficients A (equatorial rotation rate) and B (latitudinal differential rotation), we investigate their temporal evolution and polarity dependence. Our key findings are as follows: (1) The rotational profile during solar cycle 25 exhibits classic differential rotation, peaking at the equator and decreasing with latitude, along with a transition to quasi-rigid rotation above 55○. (2) A hemispherically antisymmetric polarity dependence emerges at low-mid latitudes (0○–60○), where positive-polarity fields rotate faster in the northern hemisphere, while negative-polarity fields dominate in the southern hemisphere. (3) Temporal analysis during solar cycle 25 reveals a significant negative correlation between A and B. Notably, negative-polarity fields exhibit stronger A–B anticorrelations and larger parameter variations, dominating the total magnetic field evolution.

The polar magnetic field, polar coronal holes (PCHs), and polar jets play an essential role in the generation of solar wind. To investigate their relationships during Solar Cycle 24, we applied the degradation factor of the SDO/AIA 304 Å channel correction to Liu et al.'s coronal jet counts. Using the adjusted jet data in conjunction with coronal hole information from the McIntosh Archive and polar magnetic field observations from the Wilcox Solar Observatory, we analyzed spatiotemporal correlation and hemispheric asymmetry of polar coronal jets and PCHs, and links to polar magnetic polarity changes. Our findings reveal a significant statistical correlation between the temporal variations in polar jets and the periodic behavior of PCHs. Both phenomena exhibit consistent hemispheric asymmetries throughout their evolution, which are closely associated with changes in the polar magnetic field. The cessation of polar jets and the disappearance of PCHs occur concurrently with the reversal of polar magnetic field polarity. This temporal alignment provides significant evidence supporting the hypothesis that polar jets and CHs are modulated by the sequence of magnetic polarity reversals in both hemispheres.

To distinguish the contributions of electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) in their applications in precision laser spectroscopy, we propose a real-imaginary spectrum decomposition method to investigate the transparency spectra in a four-level microwave (MW) dressed Rydberg system. We show that the opening transparency windows in the absorption spectra of probe field is a prominent character by EIT, EIT-ATS crossover, and ATS when the MW field is turned off and the intensity of the control field is adjusted. When the MW field is turned on and gradually increased, the EIT is destroyed and disappears. In addition, the most prominent characters that open a transparency window are the EIT-ATS crossover and the ATS. Then, if we further increase the intensity of the MW field, we find that the transparency windows open mainly due to the ATS. Compared to the previous considerations of this issue, which were limited to three-level systems, our four-level scheme reported here is useful for understanding the features of quantum interference in multilevel atomic systems, and has potential applications to study enhanced sensitivity, measurement spectroscopic, quantum processing, quantum communication, and transmission.