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Liping Yang Xueshang Feng Changqing Xiang Shaohua Zhang S. T. Wu 《Solar physics》2011,271(1-2):91-110
The observations both near the Sun and in the heliosphere during the activity minimum between solar cycles 23 and 24 exhibit different phenomena from those typical of the previous solar minima. In this paper, we have chosen Carrington rotation 2070 in 2008 to investigate the properties of the background solar wind by using the three-dimensional (3D) Solar?CInterPlanetary Conservation Element/Solution Element Magnetohydrodynamic (MHD) model. We also study the effects of polar magnetic fields on the characteristics of the solar corona and the solar wind by conducting simulations with an axisymmetric polar flux added to the observed magnetic field. The numerical results are compared with the observations from multiple satellites, such as the Solar and Heliospheric Observatory (SOHO), Ulysses, Solar Terrestrial Relations Observatory (STEREO), Wind and the Advanced Composition Explorer (ACE). The comparison demonstrates that the first simulation with the observed magnetic fields reproduces some observed peculiarities near the Sun, such as relatively small polar coronal holes, the presence of mid- and low-latitude holes, a tilted and warped current sheet, and the broad multiple streamers. The numerical results also capture the inconsistency between the locus of the minimum wind speed and the location of the heliospheric current sheet, and predict slightly slower and cooler polar streams with a relatively smaller latitudinal width, broad low-latitude intermediate-speed streams, and globally weak magnetic field and low density in the heliosphere. The second simulation with strengthened polar fields indicates that the weak polar fields in the current minimum play a crucial role in determining the states of the corona and the solar wind. 相似文献
994.
H. Lammer V. Eybl K. G. Kislyakova J. Weingrill M. Holmstr?m M. L. Khodachenko Yu. N. Kulikov A. Reiners M. Leitzinger P. Odert M. Xiang?Gr��? B. Dorner M. G��del A. Hanslmeier 《Astrophysics and Space Science》2011,335(1):39-50
The detection and investigation of EUV heated, extended and non-hydrostatic upper atmospheres around terrestrial exoplanets would provide important insights into the interaction of the host stars plasma environment as well as the evolution of Earth-type planets their atmospheres and possible magnetic environments. We discuss different scenarios where one can expect that Earth-like planets should experience non-hydrostatic upper atmosphere conditions so that dynamically outward flowing neutral atoms can interact with the stellar plasma flow so that huge hydrogen coronae and energetic neutral atoms (ENA) can be produced via charge exchange. By observing the size of the extended upper atmospheres and related ENA-clouds and by determining the velocities of the surrounding hydrogen atoms, conclusions can be drawn in respect to the origin of these features. Due to the large number of M-type stars in our neighbourhood and their long periods of strong and moderate stellar activity in comparison to G-stars, we expect that M-type stars represent the most promising candidates for the detection of hydrogen ENA-clouds and the subsequent study of the interaction between the host star and the planets?? upper atmosphere. We show that the low mass of M-type stars also makes them preferable targets to observe extended hydrogen clouds around terrestrial exoplanets with a mass as low as one Earth mass. Transit follow-up observations in the UV-range of terrestrial exoplanets around M-type stars with space observatories such as the World Space Observatory-UV (WSO-UV) would provide a unique opportunity to shed more light on the early evolution of Earth-like planets, including those of our own Solar System. 相似文献
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The S5 sample was monitored on a monthly basis since December 2008 at Urumqi Observatory. Most of the sources are variables and a considerable proportion (about 20%) exhibited a significant inter-month flux variability (modulation index >?4%) during the 1-year observation. 相似文献
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岛弧火山活动的数值热模拟研究是俯冲带构造热演化研究的重要方面,也是验证地表观测结果的重要方法。选取台湾-吕宋岛弧巴士段内东火山链(EVC)的甘米银活火山和西火山链(WVC)的加拉鄢死火山,根据地质和地球物理条件,进行了有限元热模拟计算。在计算模拟甘米银活火山和加拉鄢死火山现今的热流分布的基础上,分析了二者的差异。模拟结果表明,甘米银活火山顶部至周边30km热流值有明显升高,越靠近火山热流值越高且增加速率越快,岩浆房正上方的热流高达310mW.m-2。加拉鄢死火山顶部及周边热流略有升高,热流增量从周边40km处的小于3mW.m-2缓慢增加到火山顶部的15mW.m-2。 相似文献
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利用2004、2007、2010年在福建中南部沿海长期验潮站和临时验潮站获取的实测逐时潮位资料,采用基于最小二乘原理的潮汐调和分析方法,分析了福建中南部沿岸海域18个验潮站的潮汐调和常数,并根据调和常数分析了沿岸海域潮汐特征.结果表明:福建中南部沿岸海域以向南传播的半日分潮为主,传播至浮头湾以南海域后衰减明显,对应平潭至浮头湾海域的潮汐性质为半日潮,古雷半岛以南海域为不规则半日潮混合潮;福建中南部沿岸海域自北部平潭向南至诏安,平均海平面升高约25 cm,潮差减小超过3 m,平均大潮差与平均小潮差之差也减小2 m左右,理论高潮位降低约1.5m,而理论低潮位升高约2 m,潮时推迟约2h. 相似文献
999.
The status of a fishery is often defined as the probability of fishing mortality rate exceeding a perilous level for long‐term sustainability. Lobster stock assessments are often subject to large uncertainty in input data and high levels of natural variability in lobster life history processes, which calls for incorporating uncertainty associated with both indicator and management reference points in an evaluation of biological risk of overfishing. Using a Monte Carlo simulation approach, we evaluated the impacts of uncertainty in modelling on the determination of the status of the Taitung spiny lobster (Panulirus penicillatus) fishery (Taiwan), which has not been quantitatively determined despite its commercial importance. The commonly used biological reference points derived from the per recruit model (F 0.1 the fishing mortality rate where the slope of the curve of yield‐per‐recruit model is 10% of the maximum slope and F 4Q%, the fishing mortality rate that reduces the expected egg production for a cohort of female lobsters to 40% of that produced in the absence of a fishery of the egg‐per‐recruit model) were influenced by uncertainties associated with lobster life history and fishery parameters. A large uncertainty in the current fishing mortality rate (F cnr) and estimates of biological reference points (F BRPs) increased the uncertainty in determining the risk of overexploitation throughout the confidence levels of the stochastic decision‐making framework. This simulation study suggests that the target reference point of F 40% is less sensitive to the input parameters’ uncertainty than F 0.1 We suggest a further evaluation of other F‐based references points and development of biomass‐based reference points before final selection and implementation for the management of the Taitung lobster fishery. 相似文献
1000.