Sawtooth and dune auroras simultaneously driven by waves around the plasmapause

The dune aurora,at a scale of~30 kilometers,was reported recently using ground camera.The small-scale dune aurora occurs on the duskside and exhibits a monochromatic oscillation in the auroral emission,implying fundamental energy conversions.However,whether the dune auroras correspond to atmospheric waves or are associated with magnetospheric dynamics should be determined.This paper reports a dune aurora that occurred during a storm;further,we demonstrate that it was the substructure of the sawtooth aurora that was generated by plasmapause surface waves.Conjugate observations in the magnetospheric source region suggest that the exohiss waves,which are periodically modulated by the plasmapause surface wave-excited ultralow frequency wave,might be responsible for the generation of the dune aurora.Most reported dune aurora events have occurred simultaneously with sawtooth auroras,suggesting that both are plasmapause-driven cross-scale auroral structures.

Wavenumber-4 spectral component extracted from TIMED/SABER observations

The wavenumber spectral components WN4 at the mesosphere and low thermosphere(MLT)altitudes(70–10 km)and in the latitude range between±45°are obtained from temperature data(T)observed by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instruments on board the National Aeronautics and Space Administration(NASA)’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics(TIMED)spacecraft during the 11-year solar period from 2002 to 2012.We analyze in detail these spectral components WNk and obtain the main properties of their vertical profiles and global structures.We report that all of the wavenumber spectral components WNk occur mainly around 100 km altitude,and that the most prominent component is the wavenumber spectral component WN4 structure.Comparing these long duration temperature data with results of previous investigations,we have found that the yearly variation of spectral component WN4 is similar to that of the eastward propagating non-migrating diurnal tide with zonal wavenumber 3(DE3)at the low latitudes,and to that of the semi-diurnal tide with zonal wavenumber 2(SE2)at the mid-latitudes:the amplitudes of the A4 are larger during boreal summer and autumn at the low-latitudes;at the mid-latitudes the amplitudes have a weak peak in March.In addition,the amplitudes of component WN4 undergo a remarkable short period variation:significant day-to-day variation of the spectral amplitudes A4 occurs primarily in July and September at the low-latitudes.In summary,we conclude that the non-migrating tides DE3 and SE2 are likely to be the origins,at the low-latitudes and the mid-latitudes in the MLT region,respectively,of the observed wavenumber spectral component WN4.

火星全大气模式与沙尘活动模拟研究:回顾与展望

基于火星全大气模式的数值模拟研究有助于深入理解火星陆面-大气-空间环境多圈层相互耦合过程,是当今国际研究热点.模式对整个火星大气区域气象要素的描述亦可作为保障火星探测活动顺利开展的重要参考依据.沙尘活动显著影响着火星气候与天气变化,也对火星表面探测器可造成巨大安全威胁.对沙尘活动及其影响完善的模拟是目前全大气模式开发与研究工作中的重点之一.本文回顾了火星全大气模式的发展历程,概述了其构建方法,总结了相关科研成果,多角度论述了自主发展火星全大气模式的重要科研与工程价值,建议以火星沙尘活动为重点研究方向,牵引我国火星全大气模式的自主研发.模式的开发与应用涉及行星科学、空间科学、大气科学、计算机科学多领域协同合作.其开发过程势必带动我国行星科学全面发展,为相关研究领域积累经验、储备人才.

Influence of annual atmospheric tide asymmetry on annual anomalies of the ionospheric mean state

Through respectively adding June tide and December tide at the low boundary of the GCITEM-IGGCAS model (Global CoupledIonosphere–Thermosphere–Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences), we simulate theinfluence of atmospheric tide on the annual anomalies of the zonal mean state of the ionospheric electron density, and report that thetidal influence varies with latitude, altitude, and solar activity level. Compared with the density driven by the December tide, the June tidemainly increases lower ionospheric electron densities (below roughly the height of 200 km), and decreases electron densities in thehigher ionosphere (above the height of 200 km). In the low-latitude ionosphere, tides affect the equatorial ionization anomaly structure(EIA) in the relative difference of electron density, which suggests that tides affect the equatorial vertical E×B plasma drifts. Although thetide-driven annual anomalies do not vary significantly with the solar flux level in the lower ionosphere, in the higher ionosphere theannual anomalies generally decrease with solar activity.

The source of tropospheric tides

With the method of Hough mode decomposition(HMD),the tidal sources of the three main tidal components,namely,the migrating components DW1(diurnal westward propagating wavenumber 1)and SW2(semidiurnal westward propagating wavenumber 2)and the non-migrating component DE3(diurnal eastward propagating wavenumber 3),at the tropospheric altitudes(1–12 km)and in the latitude range of±60°,were obtained from National Centers for Environmental Prediction(NCEP)Climate Forecast System Reanalysis(CFSR)data during the interval from 1988 to 2011.We analyzed these sources in detail at 6 km and obtained the main properties of their yearly variations.The DW1 source was found to present a weak seasonal variation in the lower latitudes(about±10°–15°).That is,the amplitudes of the DW1 sources were larger in the summer months than in the winter months,and DW1 presented semi-annual variation near the equator(±10°)such that the DW1 source was larger at the equinoxes than at the solstices.In addition,the SW2 source was symmetric and was stronger in the southern hemisphere than in the northern hemisphere.The SW2 source presented remarkable annual and semi-annual variation such that the amplitudes were largest during the March equinox months and larger during the June solstice months.In contrast,DE3 appeared mainly around the equatorial latitudes within about±30°.The DE3 source presented remarkable semiannual variation that was larger around the solstices than the equinoxes in the southern hemisphere,and it was opposite in the northern hemisphere.By HMD,we found that the tropospheric tides were primarily dominated by some leading propagating Hough modes,specifically,the(1,1),(2,3),and(3,3)modes;the influences of the other Hough modes were negligible.The consequences of an El Niño–Southern Oscillation modulation of tidal amplitudes for the energy and momentum budgets of the troposphere may now be expected to attract attention.In summary,the above yearly variations of the main tidal sources and the Hough coefficients demonstrate that an HMD analysis can be used to investigate the tropospheric tides.

A comparison of flight energetics and kinematics of migratory Brambling and residential Eurasian Tree Sparrow

Background:Unlike resident birds,migratory birds are generally believed to have evolved to enhance flight efficiency;however,direct evidence is still scarce due to the difficulty of measuring the flight speed and mechanical power.Methods:We studied the differences in morphology,flight kinematics,and energy cost between two passerines with comparable size,a migrant(Fringilla montifringilla,Brambling,BRAM),and a resident(Passer montanus,Eurasian Tree Sparrow,TRSP).Results:The BRAM had longer wings,higher aspect ratio,lower wingbeat frequency,and stroke amplitude compared to the TRSP despite the two species had a comparable body mass.The BRAM had a significantly lower maximum speed,lower power at any specific speed,and thus lower flight energy cost in relative to the TRSP although the two species had a comparable maximum vertical speed and acceleration.Conclusions:Our results suggest that adaptation for migration may have led to reduced power output and maximum speed to increase energy efficiency for migratory flight while residents increase flight speed and speed range adapting to diverse habitats.

我国未来在轨监测火星沙尘暴的设想和方案

火星是地球的近邻,它的自转周期(约为24.6 h)及自转倾角(约为25°)都与地球的接近.火星公转周期为687 d,有稀薄的大气(主要成分为CO_(2)),有四季交替的气候变化,表面温度(夏天)最高时可达20°C.火星两极被冰(干冰和水冰的混合物)所覆盖,并有着消融和冰冻的季节周期变化.火星表面布满河道、峡谷、沟壑、冲积平原等地貌特征.在太阳系行星系统中,火星的气候环境最为接近地球.

火星沙尘暴监测方法

沙尘暴是火星表面-大气-空间构成的圈层耦合系统中一种重要的天气现象.火星沙尘暴具有显著的季节性,但对不同时空尺度和等级的沙尘暴的发生规律至今仍认识不清.沙尘暴会对火星表面探测器带来诸多影响,如降低太阳能电池板发电量、降低环境温度、扰动大气密度和风场、阻碍通信、污染仪器等,是火星表面探测任务面临的最大安全威胁之一.本文系统性地回顾了人类历史上对火星沙尘暴的监测方法及其数据反演方法,以期为我国构建完善的火星沙尘暴监测体系提供基本的方法支撑.为了更好地保障和服务我国未来火星采样返回任务和后续火星探测任务,我国应考虑尽早建立完善的火星沙尘暴监测体系,这一体系应包含的探测方法包括着陆器可见光相机监测、环绕器可见-红外多光谱相机监测和地基光学望远镜监测.通过这些不同平台、不同时空尺度的监测手段相互配合,既能有效保障我国的火星探测任务安全实施,也将极大促进我国的火星系统科学研究.

Cellbow:a robust customizable cell segmentation program

Backgrounds Time-lapse live cell imaging of a growing cell population is routine in many biological investigations.A major challenge in imaging analysis is accurate segmentation,a process to define the boundaries of cells based on raw image data.Current segmentation methods relying on single boundary features have problems in robustness when dealing with inhomogeneous foci which invariably happens in cell population imaging.Methods:Combined with a multi-layer training set strategy,we developed a neural-network-based algorithm—Cellbow.Results'Cellbow can achieve accurate and robust segmentation of cells in broad and general settings.It can also facilitate long-term tracking of cell growth and division.To facilitate the application of Cellbow,we provide a website on which one can online test the software,as well as an I mage J plugin for the user to visualize the performance before software installation.Conclusions Cellbow is customizable and generalizable.It is broadly applicable to segmenting fluorescent images of diverse cell types with no further training needed.For bright-field images,only a small set of sample images of the specific cell type from the user may be needed for training.

Delphi Survey on China's Advanced Energy Technology towards 2035

Facing the multiple challenges of low-carbon transformation,China urgently needs to adopt a new energy development path.This study used the Delphi method combined with vision analysis to analyze the advanced energy fields and gain insights into the development trends of energy technology towards 2035.The Delphi survey convened 762 domestic experts to predict the development demands and trends of advanced energy technology,and to identify important technology topics.A key list,including 91 technology topics in 9 sub-fields,was analyzed with respect to promoting economic growth,improving quality of life,and safeguarding national security.Furthermore,we conducted a research on these technology topics in context of technology research and development(R&D)level,leading countries,technology realization possibility,and constraints.The results from the Delphi survey show that the R&D level of China’s advanced energy technology is still at an elementary stage,and China,significantly,lags behind the US and the EU in the fields of advanced energy.These results reveal that insufficient R&D investment is the primary factor restricting the technology development in China’s advanced energy,though human resources,infrastructure,regulations,policies and standards also play significant roles in restricting technology development.The results from the Delphi survey may serve as a reference and help in exploring the development path of low-carbon transformation and achieving goals for addressing climate change in China.