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821.
Coronal Magnetic Flux Rope Equilibria and Magnetic Helicity 总被引:1,自引:0,他引:1
1 INTRODUCTIONObservations show that the magnetic helicity of solar magnetic structures has a predominantsign in each hemisphere of the Sun, positive in the southern hemisphere and negative in thenorthern, regardless of the solar cycle (Rust, 1994). The magnetic helicity is strictly conservedin the frame of ideal MHD (WOltjer, 1958), and approximately conserved in the presence ofresistive dissipation and magnetic reconnection in a highly conductive plajsma (Taylor, 1974;Berger, 1984; H… 相似文献
822.
J. T. Andrews 《第四纪科学杂志》1994,9(2):179-183
The importance of the Baffin-Labrador region is explained in terms of the channelling through this area of the mass flux of meltwater from the Laurentide Ice Sheet and the probable effects of this on the thermohaline circulation of the North Atlantic. The chronology of glaciation and deglaciation in the region is summarised. Reference is made to recent marine records from the Baffin Shelf. Isotopic changes recorded in foraminiferal assemblages obtained from marine sediments in the Baffin Shelf-Labrador Sea area indicate the timing and possible magnitude of meltwater fluxes during the period 14.0-11.0 ka BP. 相似文献
823.
介绍了地壳垂直运动的均衡理论 ,基于全球通量均衡基准 ,建立了任意坐标系下描述地壳垂直运动的动力学模型。该模型可表述为 L aplace方程的第二边值问题。将此模型与调和分析模型做了比较 ,认为此模型拟合精度较高 ,理论上更严密 相似文献
824.
Results of the analysis of the Comet Halley spectrophotometry,which has been carried out by H.K. Nazarchuk in 1985 with the
TVscanner of the 6-meter telescope (SAO, Russia) are presented. Timevariations in the intensities of the CN, CH, C2 and NH2bands were investigated using the series of spectra obtained inthe spectral region λλ=410÷ 510 nm. Theauto-correlation functions
for all the bands, thecross-correlation functions for C2 lines and their Fouriertransformations are calculated to determine the frequencies andperiods of the variations. A possibility
is considered thathigh-amplitude fast variations of spectral lines in Comet Halleyare caused by solar flares. The daily numbers
of solar spots andproton fluxes with energies of more then 1 MeV are compared withthe spectral variations of these lines.
It is shown that in theobservation periods the comet was projected onto an active regionof the Sun, but, among all the kinds
of solar activity, mainlythe solar proton flux with energies less than 4 MeV coincides intime with fast intensity variations
in the spectral lines. Analgorithm of cross-correlation analysis of discrete samplingseries with gaps is built, and average
cross-correlation coefficientsare calculated. 相似文献
825.
Based on the existing cumulus convective parameterization schemes,a mass flux scheme(MFS)for cumulus convective parameterization has been successfully developed by reference to thework of Chen et al.(1996).The MFS is a comprehensive scheme.In MFS,not only theimportance of the large-scale moisture convergence is taken into account,but also it includes thecumulus updrafts and downdrafts,cumulus-induced subsidence in the environmental air.entrainment,detrainment and evaporation.The interaction between the cumulus and theenvironment is described by using a one-dimensional bulk model.At the same time the schemeincludes the penetrative and shallow convections.The MFS has been successfully incorporated into the regional climate model RegCM2developed by NCAR.The new model has been applied to simulate summer monsoon characteristicsand their variations of heavy rainfall process in the Changjiang-Huaihe River Basins for threemonths from May to July 1991.The results show that the new model can successfully simulate thisrainfall prolonged process.By comparising the model outputs of RegCM2.using the Kuo schemeand the MFS.it is found that the MFS is better in simulating the surface temperature,rainfallposition and amount,and rainfall duration. 相似文献
826.
《国际泥沙研究》2022,37(5):539-552
A detailed analysis of horizontal and vertical particulate matter (PM) fluxes during wind erosion has been done, based on measurements of PM smaller than 10, 2.5, and 1.0 μm, at windward and leeward positions on a measuring field. The three fractions of PM measurement are differently influenced by the increasing wind and shear velocities of the wind. The measured concentrations of the coarser fractions of the fine dust, PM10, and PM2.5, increase with wind and shear velocity, whereas the PM1.0 concentrations show no clear correlation to the shear velocity. The share of PM2.5 on PM10 depends on the measurement height and wind speed and varies between 4 and 12 m/s at the 1 m height ranging from 25% to 7% (average 10%), and at the 4 m height from 39% to 23% (average 30%). Although general relationships between wind speed, PM concentration, and horizontal and vertical fluxes could be found, the contribution of the measuring field was very low, as balances of incoming and outgoing fluxes show. Consequently, the measured PM concentrations are determined from a variety of sources, such as traffic on unpaved roads, cattle drives, tillage operations, and wind erosion, and thus, represent all components of land use and landscape structure in the near and far surroundings of the measuring field. The current results may reflect factors from the landscape scale rather than the influence of field-related variables. The measuring devices used to monitor PM concentrations showed differences of up to 20%, which led to considerable deviations when determining total balances. Differences up to 67% between the calculated fluxes prove the necessity of a previous calibration of the devices used. 相似文献
827.
为了揭示滩涂对近岸水温影响,开展潮间带滩涂沉积物与海水之间热量交换研究。以韩国西南海岸的滩涂为例,建立滩涂沉积物温度模型,模拟不同潮汐状态下沉积物垂向剖面温度以及沉积物与水体间的热通量,并分析了季节、滩涂位置、潮位-太阳辐射相位对热通量的影响。研究表明:模拟出的沉积物温度与实测值吻合较好。沉积物与水体存在大量热量交换,且集中在淹没后的前3 h,最大热通量可达398.7 W/m2。冬季月份海水向滩涂净传热。夏季月份滩涂向水体净传热,且当滩涂淹没时刻发生在当地正午或正午过后3 h内,滩涂传递给水体的热量相对较大,达2.0 MJ/(m2·d);累积热通量随滩涂干滩率的减小而减小。研究成果为进一步深入研究滩涂影响下近岸水温变化提供了技术支撑。 相似文献
828.
利用常规观测资料及NCEP 1.0°×1.0°再分析资料,对2016年3月31日至4月2日发生于呼伦贝尔市的一次暴雪天气过程的环流形势、成因机制进行分析,以期总结出此次暴雪的特殊之处,为今后的暴雪天气预报提供可参考的经验。从天气学角度详细地分析此次暴雪过程的高低空影响系统的生消演变,特别对产生极端降水的水汽输送条件、水汽辐合情况、局地水汽聚集以及垂直运动情况进行详尽的分析。研究结果表明:此次暴雪天气过程是由短波扰动叠加低空锋区,导致斜压有效位能释放转变为扰动动能,并促使扰动发展加深为大型涡动而产生;水汽通量分布形态在一定程度上决定了水汽输送效果,“均匀狭长”的分布形态具有更高的水汽输送效率;涡度差动平流与温度平流表明动力因子与热力因子在本次过程中对垂直运动均有显著贡献,而水平散度作为直接反映质量汇集、流失的参量可以更为直观地反映垂直运动的强弱与分布;整层水汽通量散度积分作为与降水强度直接相关的物理量,对于降水量级的反映异常精准,配合中低空气流强度与方向,可对降水落区与时段进行精确判断。 相似文献
829.
利用世界上唯一深入流动沙漠腹地200 km以上的塔克拉玛干沙漠塔中站所采集的2011年4月、7月的气象资料,分析了塔克拉玛干沙漠腹地春、夏季CO2通量的变化特征及影响因素。结果表明:塔克拉玛干沙漠腹地CO2通量表现为白昼地表吸收CO2,夜间地表排放CO2,且地表吸收强度明显大于地表排放;塔克拉玛干沙漠腹地春、夏季CO2平均净吸收速率分别为0.93μmol·m2·s-1和0.82μmol·m2·s-1;CO2通量受大气稳定性影响较大,稳定大气条件利于沙漠地表CO2的释放,不稳定大气条件有利于沙漠地表CO2的吸收;此外,地表温度、土壤湿度、风速均与CO2通量呈不同程度的负相关关系。 相似文献
830.
综述了近年来人们对磁浮现与耀斑,暗条,CME等太阳表面磁活动的相关关系的研究进展。概述了磁浮现的一些观测特性和理论研究现状。最后提出了今后对磁浮现做进一步研究工作的一些设想。 相似文献