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941.
Ye Xu Dong-Rong Jiang Zhi-Yao Yu Xing-Wu Zheng Chuan-Yi Yang Yan-Ping Zhang Chun-Chuan Pei Jun-Mei Ma Jin-Jiang Sun Li-Ming Wang Deng-Rong Lu Jie-Qing Wu Yang Li Cheng-Ming Lei 《中国天文和天体物理学报》2001,(1)
1 INTRODUCTIONA violent molecular outflow is a bajsic component of star formation process. Such outflowsare observed over a wide range of wavelength from the ultraviolet to the radio, resulting fromthe interaction of highly supersonic stellar winds with the alnbiellt material and the windejection takes place in the vicinity of a newly formed star. Outflows are produced by starsof all massess but currellt outflow theories are predominantly based on observations of nearby,low-mass outflow sy… 相似文献
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Li-Cai Deng Heidi Jo Newberg Chao Liu Jeffrey L. Carlin Timothy C. Beers Li Chen Hsu-Tai Lee Carl J. Grillmair Puragra Guhathakurta Zhan-Wen Han Jin-Liang Hou Sebastien Lepine Jing Li Xiao-Wei Liu Kai-Ke Pan J. A. Sellwood Bo Wang Hong-Chi Wang Fan Yang Brian Yanny Hao-Tong Zhang Yue-Yang Zhang Zheng Zheng Zi Zhu 《天体物理学报》2012,(7):735-754
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In mean-field dynamo theory, the electromotive force term 〈u′ × B′〉 due to small-scale fields connects the small-scale magnetic field with the large-scale field. This term is usually approximated as the α-effect, assumed to be instantaneous in time and local in space. However, the approximation is valid only when the magnetic Reynolds number Rm is much less than unity, and is inappropriate when Rm ? 1, which is the condition satisfied in the Earth's core or solar convection zone. We introduce a function φ qr as a non-local and non-instantaneous generalization of the usual α-effect and examine its behaviour as a function of Rm in the range 1/64 ≤ Rm ≤ 10 for a kinematic dynamo model. We use the flow of G.O. Roberts 1972 (Phil, Trans. Roy. Soc. London Ser. A, 1972, 271, 411–454), which is steady and has non-zero helicities and two-dimensional periodicity. As a result, we identify three regions in Rm space according to the behaviour of the function φ qr : (i) Rm ? 1/4, where the function φ qr is local and instantaneous and can be approximated by the traditional α and β effects, (ii) 1/4 ? Rm ? 4, where the deviation from the traditional α and β effects increases and non-localness and non-instantaneousness increase, and (iii) Rm ? 4, where boundary layers develop fully and non-localness and non-instantaneousness are prominent. We show that the non-local memory effect for Rm ? 4 strongly affects the dynamo action and explains an observed augmentation of the growth rate in the dispersion relation. The results imply that the non-local memory effect of the electromotive force should be important in the geodynamo or the solar dynamo. 相似文献