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M.O. Riazantseva O.V. Khabarova G.N. Zastenker J.D. Richardson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,40(12):1802-1806
Sharp (<10 min) and large (>20%) solar wind ion flux changes are common phenomena in turbulent solar wind plasma. These changes are the boundaries of small- and middle-scale solar wind plasma structures which can have a significant influence on Earth’s magnetosphere. These solar wind ion flux changes are typically accompanied by only a small change in the bulk solar wind velocity, hence, the flux changes are driven mainly by plasma density variations. We show that these events occur more frequently in high-density solar wind. A characteristic of solar wind turbulence, intermittency, is determined for time periods with and without these flux changes. The probability distribution functions (PDF) of solar wind ion flux variations for different time scales are calculated for each of these periods and compared. For large time scales, the PDFs are Gaussian for both data sets. For small time scales, the PDFs from both data set are more flat than Gaussian, but the degree of flatness is much larger for the data near the sharp flux change boundaries. 相似文献
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The purpose of this work is to improve the k-ω-γ transition model for separationinduced transition prediction. The fundamental cause of the excessively small separation bubble predicted by k-ω-γ model is scrutinized from the perspective of model construction. On the basis,three rectifications are conducted to improve the k-ω-γ model for separation-induced transition.Firstly, a damping function is established via comparing the molecular diffusion timescale with the rapid pressure-strain timescale... 相似文献
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Rodrigo A. Miranda Abraham C.-L. Chian Erico L. Rempel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We analyze the multifractal scaling of the modulus of the interplanetary magnetic field near and far upstream of the Earth’s bow shock, measured by Cluster and ACE, respectively, from 1 to 3 February 2002. The maximum order of the structure function is carefully estimated for each time series using two different techniques, to ensure the validity of our high-order statistics. The first technique consists of plotting the integrand of the pth order structure function, and the second technique is a quantitative method which relies on the power-law scaling of the extreme events. We compare the scaling exponents computed from the structure functions of magnetic field differences with the predictions obtained by the She–Lévêque model of intermittency in anisotropic magnetohydrodynamic turbulence. Our results show a good agreement between the model and the observations near and far upstream of the Earth’s bow shock, rendering support for the modelling of universal scaling laws based on the Kolmogorov phenomenology in the presence of sheet-like dissipative structures. 相似文献
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Energy must be continually supplied to the solar corona to maintain both its average temperature and its high energy manifestations. The energy is supplied by photospheric motions and the magnetic field acts both to transmit this energy to the corona and as the furnace in which the energy is stored. The means by which the energy is dissipated and transformed into the actual forms we observe is the activation of current sheets. We conjecture here the properties of such current sheets as derived by both energetical arguments and numerical evidence of the self-organization of a system of currents in a highly turbulent medium. The consequences of the appearance of spatial and temporal intermittency on the different aspects of solar acitvity are also discussed. 相似文献
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