Fast blue optical transients (FBOTs) represent one of the most exotic astrophysical transients, exhibiting unusually strong emission across X-ray, optical, and radio wavelengths. Their physical origins remain highly debated, with proposed explanations ranging from stellar explosion to tidal disruption event (TDE). Here we report observations of the most luminous FBOT, AT 2024wpp whose post-peak luminosity rebrightens in X ray and becomes flattening in optical in a manner follows the decay rate characteristic of TDEs (L_ bol∝ t^-5/3). This invokes energy contribution of accretion by a central compact object, getting further corroborations from hardening of X-ray spectral index and detection of outflow inferred from the emission lines at similar phase. Detailed modeling of luminsoity evolution favors a coalesce explosion of a 34 M_⊙ Wolf-Rayet star with a 15 M_⊙ black hole (BH), demonstrating that some FBOTs may be associated with TDE of a stellar blackhole.

Ion cyclotron waves are widely present upstream from the Martian bow shock, with frequencies near the local proton cyclotron frequency in the spacecraft frame. The waves propagate quasi-parallel to the background magnetic field, and are associated with the solar wind picking up newly-ionized hydrogen from the Martian exosphere. In this work, a typical ion cyclotron wave event was observed by MAVEN (Mars Atmosphere and Volatile Evolution) probe upstream from the Martian bow shock. The further MVA (minimum variance analysis) results for this event show that the magnetic field perturbations are left-handed polarized and propagate quasi-parallel (the propagation angle θ = 12.37∘) to the background magnetic field. The relationship between the plasma perturbations and magnetic field perturbations is theoretically derived for slow magnetosonic, Alfv{\'e}n, and fast magnetosonic waves based on the magnetohydrodynamic theory. If we take the wave propagation angle θ = 12.37∘ estimated from the MVA method, the theoretically expected density perturbation and velocity perturbation along the background magnetic field are in serious disagreement with the MAVEN data. Through fitting the plasma density perturbation, velocity perturbation, and magnetic field perturbation, it is found that the ion cyclotron wave event can be explained by the superposition of oblique fast magnetosonic waves with a propagation angle of 63∘ relative to the background magnetic field and parallel propagating Alfv{\'e}n waves. The results are helpful to further understand the physical nature of the observed ion cyclotron wave-related perturbations upstream from the Martian bow shock, and have guiding implications for the re-modeling and numerical simulation of the plasma physical processes therein.

Alfvén ion cyclotron waves (ACWs) and kinetic Alfvén waves (KAWs) are found to exist at <0.3 au observed by Parker Solar Probe in Alfvénic slow solar winds. To examine the statistical properties of the background parameters for ACWs and KAWs and related wave disturbances, both wave events observed by Parker Solar Probe are selected and analyzed. The results show that there are obvious differences in the background and disturbance parameters between ACWs and KAWs. ACW events have a relatively higher occurrence rate but with a total duration slightly shorter than KAW events. The median background magnetic field magnitude and the related background solar wind speed of KAW events are larger than those of ACWs. The distributions of the relative disturbances of the proton velocity, proton temperature, the proton number density, and β cover wider ranges for ACW events than for KAW events. The results may be important for the understanding of the nature and characteristics of Alfvénic slow solar wind fluctuations at ion scales near the Sun, and provide the information of the background field and plasma parameters and the wave disturbances of ACWs and KAWs for further relevant theoretical modeling or numerical simulations.

Ion cyclotron waves (ICWs) are one kind of plasma waves whose frequency is close to the ion cyclotron frequency. They exist widely in the upstream of Mars, and the frequency observed by satellites is generally near the proton cyclotron frequency. ICWs are byproducts in the production processes of pick-up ions. The occurrence of ICWs constitutes, in principle, an indirect signature of the presence of newborn planetary protons. ICWs in the upstream of Mars have received much attention since they were first reported in 1990. In this review, we summarize the research progress of ICWs in the upstream of Mars, including the observation of ICWs, the wave generation mechanism, their statistical properties, and related future research trends.

II型多功能天文经纬仪是中国科学院云南天文台为了满足利用多台仪器组网监测本地铅垂线变化信息的需求研制的一种地面天体测量仪器。仪器的图像采集系统使用3台非制冷CCD作为采集终端,工作在外触发模式,利用望远镜控制系统提供的外触发信号按照观测时序触发相机。介绍了望远镜的具体工作模式,对图像采集系统的工作流程给予说明;介绍了采集系统的硬件构成、软件框架和涉及的主要编程方法;给出了图像采集系统的软件工作界面和所采集的图像,并对拍摄的恒星像成像质量进行了简单分析。

We report efficient generation of 671 nm red light based on quasi-phase-matched second harmonic generation of 1342 nm in LiNbO3 waveguides. The design method and fabrication process of the high-quality annealed proton-exchanged periodically poled channel waveguides were presented. A continuous-wave 1.71 mW red light was obtained with a single-pass conversion efficiency of 47%·W-1·cm-2, which is 88% that of the theoretical value. While for 1 mW quasi-continuous-laser input, the corresponding peak power being 2 W, the conversion efficiency reached up to 60%. Our results indicate that the annealed proton-exchanged periodically poled LiNbO3 waveguide is promising for high-efficiency and low power consumption nonlinear generation of visible light.

Electromagnetic waves (EMWs) near the proton cyclotron frequency fcp are transverse left-handed (LH) or right-handed (RH) polarized waves, and are ubiquitous in the solar wind. However, the characteristics of these waves in the sheath regions of interplanetary coronal mass ejections (ICMEs) are poorly understood. Through a comprehensive survey of Wind magnetic field and plasma data using dynamic spectra and repeated filtering analyses, 700 EMW events (7.1% of the analysis time) are identified in the 62 ICME sheath regions associated with quasi-perpendicular shocks involved with a low shock Mach number Mf and low upstream β1. In the ICME sheath regions, outward (inward)-propagating LH (RH) EMWs have relatively higher counts and longer duration than inward (outward)-propagating LH (RH) EMWs in the plasma frame, consistent with previous STEREO observations. The spatial distributions of the magnetic field, plasma, and frequency parameters of EMWs are also presented in both spacecraft and plasma frames, especially the proton (alpha) temperature anisotropy , α abundance Nα/Np, and normalized differential alpha-proton speed Vd/VA. After removing the Doppler shift, 81.1% (59%) of all outward (inward)-propagating LH EMWs have a frequency below (above) 0.5fcp, while 68.3% (64%) of all outward (inward)-propagating RH EMWs have a frequency smaller (greater) than 0.5fcp. Further investigations of local plasma parameters reveal that different excitation mechanisms for EMWs are in different subregions of the ICME sheath regions. These results are helpful in understanding the important role of EMWs in the solar wind–ICME coupling process with different sheath regions.

In this work, we propose a new scheme to generate frequency-doubled vortex beams from a radially poled LiNbO3 micro-ring resonator based on nonlinear Cherenkov radiation. The near-infrared fundamental wave is resonant in the micro-ring, while the second harmonic is emitted from the resonator along the Cherenkov phase-matching direction. The topological charge of the emitted second-harmonic vortex beam is determined by both the azimuthal order of the whispering galley modes and the number of nonlinear grating elements. The field distribution and the conversion efficiency of the emitted vortex beam are investigated.

Although it is believed that Alfven waves can be present in the form of torsional modes in interplanetary magnetic flux ropes, convincing observational evidence remains elusive. In this Letter, we report the detection of Alfven waves embedded within an interplanetary magnetic cloud (MC) on 2003 March 20, which exhibited features quite different from those upstream and downstream. The magnetic field inside the MC underwent alternate rotations along an arc through a relatively small angle in the plane perpendicular to the minimum variance direction, which seems consistent with the appearance of torsional modes. A significant poloidal motion of plasma existed in the MC, thus it is possible that the field-aligned helical plasma flow was mixed with Alfven waves exhibiting high correlation between plasma velocity and the magnetic field.

The compressed and turbulent sheath regions of interplanetary magnetic clouds (IMCs) provide a natural laboratory to study electromagnetic waves (EMWs) around the proton cyclotron frequency f(cp). Based on the Morlet wavelet spectral analysis, the repeated filtering analysis and the minimum variance analysis of high-resolution magnetic field data from the STEREO spacecraft, 81 EMW events are identified in the sheath regions of six IMCs. These EMWs are all transverse, almost circularly polarized, and quasi-parallel propagating along the background magnetic field B-0. They can be left-handed (LH) or right-handed (RH) polarized in the spacecraft frame, where the occurrence rate of the LH-polarized EMWs is higher than that of RH-polarized ones, consistent with previous observations in the solar wind. Also, a comparative analysis of polarization sense of these EMWs has been made in the spacecraft and plasma frames. Our results show that more than half of EMW events suffer a polarization reversal from the spacecraft to plasma frames, which are deduced to propagate inward relative to the solar wind flow. Others are outward-propagating waves. In the plasma frame, the outward-propagating LH-EMWs and inward-propagating RH-EMWs have relatively higher occurrence rates than the inward-propagating LH-EMWs and outward-propagating RH-EMWs, respectively. Furthermore, in the plasma frame all the frequencies of LH-EMWs are below f(cp), but the RH-EMW frequencies can exceed f(cp). These results are helpful in understanding the physical properties of EMWs and their roles in the sheath regions of IMCs.

Directional discontinuities (DDs) are common structures in the interplanetary space. Correctly determining the normal of a DD is important to understand the changes of phase fronts of magnetic fields adjacent to a discontinuity as well as helpful for the applications in many regimes of space physics research. In this work, we propose a new scheme to estimate the normal directions of DDs by finding the smallest standard deviation of normal magnetic fields derived from the cross product of magnetic fields on both sides of the discontinuity, based on the idea that the phase fronts of the adjacent magnetic fields are closely parallel to the DD plane. By comparing with the normal direction determined from Cluster multiple spacecraft, we show that our scheme can provide the same accuracy as that from the multispacecraft estimation. Moreover, our scheme gives a consistent result of normal estimations at different Cluster spacecraft. We notice that in some cases, the normal directions derived from the minimum variance analysis have large differences between those of multispacecraft method and our scheme implying significant influence of the kinetic effect of particles in the transition region of the discontinuity. A few events of STEREO B observations are further studied to show that our scheme can be applied to DDs in single‐spacecraft measurements with even small rotation of magnetic fields across the discontinuities. With the help of an accurate normal estimation, we can understand the variations of magnetic field phase fronts in the vicinity of discontinuities.

Atmospheric refraction is a major correction term which directly influences the position measurement of celestial bodies.The existing atmospheric refraction table only adopts the average atmospheric density of observation area,while the actual distribution of atmospheric density is affected by the geographical environment,building and meteorological environment of observation station.Therefore,for highly-accurate observation,it is not enough to make correction by adopting unitary refraction table.The fundamental method to improve atmospheric refraction correction accuracy is to establish atmospheric refraction measurement model of observation station.Based on the characteristics of the multi-function theodolite,this paper proposes approach which can get the instantaneous astronomical latitude value only by using apparent zenith distance of the meridian direction.Meanwhile,we have separately established the actual atmospheric refraction measurement modal of meridional direction and multiple directions.The compiling of star-choosing program is also made to meet some conditions (∑ tan z →0) so that the system errors affecting the measurement of instantaneous astronomical latitude can be reduced artfully.

Narrow bipolar pulses (NBE) are special flashes in thunderstorms which are different from regular incloud discharges and cloud-to-ground discharges.They can produce intense radiation in both VLF/LF and VHF bands.To explore the meteorological environment and discharge characteristics of NBE,locations and radiation strength of 608 positive NBE and 82 negative NBE detected in a thunderstorm day are analyzed using the dual band 3D lightning locating system in Chongqing.Results show that positive NBE occur at the altitude of 7-15 km,with the average altitude of 10.0 km.According to the radar reflectivity of positive NBE,they can be divided into three groups.49 positive NBE,which occur in the thunderstorm cores (reflectivity),are categorized as Group Ⅰ.350 NBE occurring in regions outside cores with the reflectivity higher than 5 dBZ are categorized as Group Ⅱ.The rest 209 positive NBE are Group Ⅲ.The radiation strength of these three groups are in descending order on both bands.The mean value of all positive NBE VLF/LF electric field change peaks normalized to 100 km is 13.4 V · m-1.The mean value of their VHF radiant powers is 73.5 kW.Negative NBE are generally produced in two regions in the thunderstorm.Among 82 negative NBE,72 of them occur at the altitude of 16-20 km,and the average altitude is 18.0 km.They occur on or beside tops of thunderstorms with 30-35 dBZ echo heights higher than 18 km.The mean value of their VLF/LF electric field change peaks normalized to 100 km is 42.7 V · m-1.The mean value of the VHF radiant powers is 76.9 kW.10 negative NBE occur at the altitude of 4-10 km,whose average altitude is 6.0 km.They all occur in thunderstorm cores.The mean value of VLF/LF electric field change peaks normalized to 100 km is 2.7 V · m-1.The mean value of VHF radiant powers is 18.2 kW.According to statistical results,the radiation strength of the upper negative NBE is mostly stronger than those of positive NBE and the lower negative NBE on VLF/LF band.In VHF band,values are similar,both of which are stronger than the lower negative NBE.The radiation strength of the lower negative NBE is weaker than that of positive NBE in both bands.

Ulysses magnetic and plasma data are used to study hourly scale Alfvenic fluctuations in the solar polar wind. The calculated energy ratio R-vA(2) (cal) of inward to outward Alfven waves is obtained from the observed Walen slope through an analytical expression, and the observed R-vA(2) (obs) is based on a direct decomposition of original Alfvenic fluctuations into outward-and inward-propagating Alfven waves. The radial variation of R-vA(2) (cal) shows a monotonically increasing trend with heliocentric distance r, implying the increasing local generation or contribution of inward Alfven waves. The contribution is also shown by the radial increase in the occurrence of dominant inward fluctuations. We further pointed out a higher occurrence (similar to 83% of a day in average) of dominant outward Alfvenic fluctuations in the solar wind than previously estimated. Since R-vA(2) (cal) is more accurate than R-vA(2) (obs) in the measurement of the energy ratio for dominant outward fluctuations, the values of R-vA(2) (cal) in our results are likely more realistic in the solar wind than those previously estimated as well as R-vA(2) (obs) in our results. The duration ratio R-T of dominant inward to all Alfvenic fluctuations increases monotonically with r, and is about two or more times that from Voyager 2 observations at r >= 4 au. These results reveal new qualitative and quantitative features of Alfvenic fluctuations therein compared with previous studies and put constraints on modeling the variation of solar wind fluctuations.

The light lever detector can be used to detect error of angular encoder so as to improve precision of motion control of astronomical telescope. The device needs to achieve high precision of rotation control and automatic detection. According to the functional requirements of the detecting device,the control system of the angle encoder detection device is designed based on the programmable multi-axis motion controller (PMAC), hardware platform of the system is built,and the application software of the control system is compiled,and the synchronous between the CCD camera and data acquisition and exposure the encoder is implemented. Experimental results indicate that absolute value of repetitive positioning error of the turntable is less than 4″,which meet the requirements of the encoder detection system.

For solving the problems of offshore heavy oil exploitation,researchers developed the multiple thermal fluid thermal recovery technology.Compared with steam,multiple thermal fluids can significantly reduce the viscosity of heavy oil and increase the reservoir pressure,improve the mining efficiency.Based on real gas state equation and mixed rules,the model for flow and heat transfer of multiple thermal fluids is established to compare with flow and heat transfer of steam injected in wellbore,detailed conditions of two kinds of thermal medium in wellbore are analyzed.The results show:compared with steam under the same injection temperature and rate injected in wellbore,pressure and temperature of the multiple thermal fluid wellbore drop faster.Bottom hole pressure is larger and temperature is lower when it reaches wellbore bottom,and the temperature difference between formation and reservoir is smaller,heat loss is less,but heat is lower,oil heating range is smaller.To achieve the same heating effect with steam,it need increase injection rate and injection temperature of the multiple thermal fluids.At the same time,due to the effect of CO2 and N2,reservoir temperature distribution is more uniform,and more heat is injected into reservoir,so heat range of oil is bigger,the multiple thermal fluid extraction effect is better.

The Moon-solar wind interaction results in the formation of a complicated lunar space plasma environment. Here, we investigate the solar wind turbulence around the Moon using the magnetic field observed by the dual-probe mission Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS). Structure functions in a time range on kinetic scales are computed to measure the scaling index., the spatial distribution of which reveals the global aspects of the lunar space plasma and shows the dependence on the local instability. On the lunar nightside, in the plasma void, the dominating magnetic pressure over the thermal pressure restrains the turbulence, and a quiet zone is built with xi << xi(0), where xi(0) = 0.36 is the scaling index in the ambient solar wind. Downstream in the lunar wake, xi is elevated gradually and goes above xi(0) at a radial distance of similar to 3R(m) (lunar radius), which implies that the plasma refilling process in the lunar wake begins to generate the local turbulence. On the dayside around the subsolar point, xi is enhanced at a low altitude of similar to 200 km, where the solar wind turbulence might be strengthened due to interaction with the lunar source plasma. The largest scaling indices lie around the day-night terminator with xi > 0.65, and the observed dawn-dusk asymmetry could be an effect of the magnetic field not being parallel with the solar wind. The correspondence between the enhanced scaling index and the local instability also raises new questions about the description of solar wind turbulence.

Assuming that the observed Alfven waves in the solar wind are the superposition of inward-and outward-propagating Alfven waves, we obtain an analytical relation from which the observed Walen slope R-W can give a theoretical estimate of the amplitude ratio R-vA of inward to outward waves. From the Wind data at 1 AU, we select 37 Alfven wave events classified observationally as three kinds: dominant outward Alfven waves with vertical bar R-W vertical bar >= 0.75 (Class A), dominant outward Alfven waves with vertical bar R-W vertical bar < 0.75 (Class B), and dominant inward Alfven waves with vertical bar R-W vertical bar < 0.75 (Class C). For Class A events the theoretical predictions of R-vA based on R-W deviate from the wave amplitude observations, but for Class B and C events the theoretical predictions agree well with related observations, being a direct observational evidence that the superposition of inward and outward Alfven waves can cause the subunity of R-W. A simple simulation is made with a white Gaussian noise to demonstrate that a small noise could reproduce the observed properties of all three kinds of events cause the measured parameters of waves with vertical bar R-W vertical bar >= 0.75 in Class A to deviate significantly from the true values more than waves with vertical bar R-W vertical bar < 0.75. The simulation implies that the observational results based on wave amplitudes seem. reliable only for waves with vertical bar R-W vertical bar < 0.75. The R-vA ratios calculated from the analytical relation based on R-W are closer to true values than those obtained from wave amplitude observations.

In this study, three methods of analysis are compared to test the Walen relation. Method 1 requires a good de Hoffmann-Teller ( HT) frame. Method 2 uses three components separately to find the frame that is slightly modified from Method 1. This method is intended to improve the accuracy of the HT frame and able to demonstrate the anisotropic property of the fluctuations. The better the relation is, the closer the slope of a regression fitting the data of plasma versus Alfven velocities is to 1. However, this criterion is based on an average HT frame, and the fitted slope does not always work for the Walen test because the HT frame can change so fast in the high-speed streams. We propose Method 3 to check the Walen relation using a sequence of data generated by taking the difference of two consecutive values of plasma and Alfven velocities, respectively. The difference data are independent of the HT frame. We suggest that the ratio of the variances between plasma and Alfven velocities is a better parameter to qualify the Walen relation. Four cases in two solar wind streams are studied using these three methods. Our results show that when the solar wind HT frame remains stable, all three methods can predict Alfvenic fluctuations well, but Method 3 can better predict the Walen relation when solar wind contains structures with several small streams. A simulated case also demonstrates that Method 3 is better and more robust than Methods 1 and 2. These results are important for a better understanding of Alfvenic fluctuations and turbulence in the solar wind.

An analytical comparative study of a two-fluid and a gyrokinetic model of kinetic Alfven waves (KAWs) is presented for various solar and space plasma environments. Based on the linear KAW dispersion relation for gyrokinetics (Howes et al. 2006), the wave group velocity and electromagnetic polarizations are obtained analytically. Then the gyrokinetic wave properties are compared with those of the two-fluid model. The results show that both models agree well with each other not only in the long wavelength regime (>> the ion gyroradius rho(i)) for all cases considered, but also in wavelengths similar to rho(i) and <> 1) ion/electron temperature ratio T-0i/T-0e, respectively. However, the fluid model calculations deviate strongly from the gyrokinetic model at scales < rho(i) for a relatively low T-0i/T-0e due to the electron gyroradius effect. Meanwhile, the plasma beta(i) can make the gyrokinetic dispersion relation of KAWs become complex and sometimes have an oscillation-like structure. With the inherent simplicity of the fluid theory, these results may improve our understanding of the applicability of the two-fluid model, and may have important implications for computer simulation studies of KAWs in the solar and space plasma surroundings.