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Two possible mechanisms for vortex self-organization

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science china Earth {2. 2006年第2期49卷 202-211页

作者： LUO Zhexian2. ZHOU Xiuji1 & GAO Shouting3.1. chinese {2. of Meteorological sciences, Beijing 100081,{3. 2. Department of space Information science, Nanjing University of Information science and Technology, Nanjing 2.0044,{3. 3. Institute of Atmospheric Physics, chinese academy of sciences, Beijing 10002.,{3. Department of Environmental science Nanjing University of Information Science and Technology Nanjing China chinese academy of Meteorological {2. Beijing China Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China

The vortex self-organization is investigated in this paper by four groups of numerical experiments within the framework of quasi-geostrophic model, and based on the experimental results two types of possible mechanisms for vortex self-organization are suggested. The meso-scale to-pography may enable separated vortices to merge into a larger scale vortex; and the interaction of meso-γ and meso-β scale systems may make separated vortices to self organize a typhoon-like vor-tex circulation.

关键词： vortex, self-organization, meso-scale topography, interaction of different scales.

A tentative study for the prediction of the CME related geomagnetic storm intensity and its transit time

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science china(Technological {2.) 2005年第6期48卷 648-668页

作者： ZHAO Xinhua1,2.& FENG Xueshang1,3.1. SIGMA Weather Group, Key Laboratory of space Weather, Center for space science and Applied Re-search,{3., Beijing 100080, china 2. Graduate School of the{3., Beijing 10003., china 3. School of Geophysics and Geoinformation Systems, china University of Geo{12., Beijing 100083. china SIGMA Weather Group Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China Graduate School of the chinese academy of sciences Beijing China School of Geophysics and Geoinformation Systems China University of Geosciences Beijing China

Using 80 CME-ICME events during 1997.1―2.02.9, based on the eruptive source locations of CMEs and solar magnetic field observation at the photosphere, a current sheet magnetic coordinate (CMC) system is established in order to study the propagation of CME and its geoeffectiveness. In context of this coordinate system, the effect of the eruptive source location and the form of heliospheric current sheet (HCS) at the eruptive time of CME on the geomagnetic storm intensity caused by CME and the CME’s transit time at the Earth is investigated in detail. Our preliminary conclusions are: 1) The geomagnetic disturbances caused by CMEs tend to have the so-called “same side-opposite side effect”, i.e. CMEs erupt from the same side of the HCS as the earth would be more likely to arrive at the earth and the geomagnetic disturbances associated with them tend to be of larger magnitude, while CMEs erupting from the opposite side would arrive at the earth with less probability and the corresponding geomagnetic disturbance magnitudes would be relatively weaker. 2. The angular separation between the earth and the HCS affect the corresponding disturbance intensity. That is, when our earth is located near the HCS, adverse space weather events occur most probably. 3. The erupting location of the CME and its nearby form of HCS will also affect its arrival time at the earth. According to these conclusions, in this context of CMC coordinate we arrive at new prediction method for estimating the geomagnetic storm intensity (Dstmin) caused by CMEs and their transit times. The {2. of the empirical model for 80 CME-ICME events shows that the relative error of Dst is within 3.% for 59% events with Dstmin≤?50 nT, while the averaged absolute error of transit time is lower than 10 h for all events.

关键词： coronal mass ejections, current sheet magnetic coordinate system, geomagnetic storm intensity, transit time, prediction method.

Prediction method for October 2.03.solar storm

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science china(Technological {2.) 2006年第5期49卷 629-640页

作者： XIE Yanqiong1, 2. 3. WEI Fengsi1, FENG Xueshang1 & ZHONG Dingkun1, 2.1. State Key Laboratory of space Weather, Center for space science and Applied Research,{3., Beijing 100080, china 2. Graduate School,{3., Beijing 10003., china 3. Institute of Meteorology, PLA University of science and Technology, Nanjing 2.1101, china State Key Laboratory of space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China Graduate School Chinese Academy of Sciences Beijing China Institute of Meteorology PLA University of Science and Technology Nanjing China

Aiming at two intense shock events on October 2. and 2., 2.03. this paper presents a two-step method, which combines synoptic analysis of space weather ——“observing” and quantitative prediction ——“palpating”, and then uses it to test predictions. In the first step of “observing”, on the basis of observations of the solar source surface magnetic field, interplanetary scintillation (IPS) and ACE spacecraft, we find that the propagation of the shocks is asymmetric relative to the normal direction of their solar sources, and the Earth is located near the direction of the fastest speed and the greatest energy of the shocks. As the two fast ejection shock events, the fast explosion of coronal mass of the extremely high temperature, the strong magnetic field, and the high speed background solar wind are also helpful to their rapid propagation. In the second step of “palpating”, we adopt a new membership function of the fast shock events for the ISF method. The predicted results show that for the onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8% and 6.7%; and for the magnetic disturbance magnitude, the relative errors are 4.1% and 3.1%, re- spectively. Furthermore, the comparison among the predicted results of our two-step method with those of five other prevailing methods shows that the two-step method is advantageous. The results tell us that understanding the physical features of shock propagation thoroughly is of great importance in improving the prediction precision.

关键词： solar storm, interplanetary shock, interplanetary scintillation, two-step method, ISF method.

Nonlinear interactions between gravity waves and background winds

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Progress in Natural science:Materials International 2007年第6期17卷 639-644页

作者： Liu Xiao1,2.and Xu Jiyao1(1. State Key Laboratory for space Weather, Center for space {2. and Applied Research,{3., Beijing 100080, china 2. Graduate University of{3., Beijing 10003., china) State Key Laboratory for space Weather Chinese Academy of Sciences Beijing 100080 China Center for space science and Applied Research Chinese Academy of Sciences Beijing 100080 China Graduate University Chinese Academy of Sciences Beijing 100039 China

Using the nonlinear propagating gravity waves (GW) model in the two-dimensional compressible atmosphere and the linear GW theory, the process of GW propagation in different background winds, e.g. the direction of the background wind is opposite to (dead wind) or the same as (tail wind) the direction of the horizontal phase velocity of GW, is studied. The results show that the dead wind prolongs the vertical wavelength and accelerates GW propagation. Therefore, GW propagates up to a higher height becomes instable in a short time and eventually induces an inverse jet flow. Then, the vertical wavelength is becoming short due to the nonlinear interactions between GW and the inverse jet flow. The vertical wavelength and group velocity decrease after GW propagates into the tail wind. The initial instable time is delayed. Although most of GW is trapped in the instable region, some of GW propagates above the instable region. Compared with GW propagation in the tail wind, the nonlinear interactions between GW and the dead wind are also strong. In contrast, the linear GW theory predicts that GW can propagate freely in the dead wind. The vertical wavelength simulated by the nonlinear numerical model is different from that predicted by the linear theory greatly after GW propagates into the dead wind.

关键词： gravity waves background winds vertical group velocity vertical wavelength nonlinear interactions.

The gravity wave instability induced by photochemistry in summer polar mesopause region

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chinese science Bulletin 2000年第3期45卷 267-272页

作者： Center for space science and Applied Research,{2., Beijing {3., china Laboratory of Numeric Study of Heliospheric Physics,{2., Beijing {3., china Center for space science and Applied Research Chinese Academy of Sciences Beijing China Laboratory of Numeric Study of Heliospheric Physics Chinese Academy of Sciences Beijing China

The effect of diabatic process due to the photochemical heating and cooling on the gravity wave propagation in middle atmosphere is studied. A linear gravity wave model which considers the diabatic process is established. The unstable region and the growth rate of the gravity wave caused by photochemistry are calculated. And the comparison between the model and the adiabatic gravity wave theory of pure dynamics is made. The results indicate that the photochemical heating process can induce the instability of gravity wave at mesopause. The intensity of the instability becomes stronger as the temperature decreases. The temperature feature and the altitude characteristics of the instability are consistent with the observation. Therefore, the instability of the gravity wave induced by photochemistry may be an important mechanism in polar mesopause region in summer.

关键词： photochemistry instability gravity wave growth rate.

Simulation studies of high-latitude magnetospheric boundary dynamics

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science china(Technological {2.) 2004年第4期47卷 421-435页

作者： PU Zuyin1, SHI Quanqi1,3. XIAO Chijie1, FU Suiyan1, ZHANG Hui1,2. ZONG Qiugang2.& LIU Zhenxing3.1. School of Earth and {2. sciences, Peking University, Beijing 100871, china 2. Center for {2. Physics, Boston University, 72. Commonwealth Avenue, Boston, MA 02.15, USA 3. Center for {2. science and application Research, chinese academy of sciences, Beijing 100080, china School of Earth and space sciences Peking University Beijing China Center for space science and {2. Research Chinese Academy of Sciences Beijing China Center for space Physics Boston University Boston USA

Magnetic reconnection at the high-latitude magnetopause is studied using 2.5-dimensional Hall-MHD simulation. Concentric flow vortices and magnetic islands appear when both Hall effect and sheared flow are considered. Plasma mixing across the magnetopause occurs in the presence of the flow vortices. Reconnected structure generated in the vicinity of the subsolar point changes its geometry with increasing flow shear while moving to high latitudes. In the presence of flow shear, with the Hall-MHD reconnection a higher reconnection rate than with the traditional MHD is obtained. The out-of-plane components of flow and magnetic field produced by the Hall current are redistributed under the action of the flow shear, which makes the plasma transport across the boundaries more complicated. The simulation results provide some help in understanding the dynamic processes at the high latitude magnetopause.

关键词： magnetopause, entry layer, magnetic reconnection, vortex reconnection, Hall effect, flow shear.

Formal analysis and design of multi-party fair exchange protocols

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science in china(Series F) 2006年第2期49卷 155-174页

作者： QING Sihan1,2.3.& LI Gaicheng1,3.1. Engineering Research Center for Information Security Technology, Institute of Software,{2., Beijing 100080, china 2. Beijing Zhongke Ansheng Corporation of Information Technology, Beijing 100080, china 3. Graduate School of the{2., Beijing 10003., china Engineering Research Center for Information Security Technology Institute of Software Chinese Academy of Sciences Beijing China Beijing Zhongke Ansheng Corporation of Information Technology Beijing China Graduate School of the chinese academy of sciences Beijing China

Based on the origin of message items and channel combination between transacting parties, and events and relations among events, this paper presents a concise, precise, and hierarchical model for general fair exchange protocols, formally specifies various security requirements which are able to reflect inherent requirements for fair exchange protocols more rigorously, and partition these security requirements with fine granularity. This work helps analyze, debug, and design multi-party fair exchange protocols more effectively and elaborately,

关键词： fair exchange logical protocol formal model security requirement.

Wavelet Analysis of the Schwabe Cycle Properties in Solar Activity

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chinese Journal of Astronomy and Astrophysics 2004年第6期4卷 578-582页

作者： Gui-Ming LeNational Astronomical Observatories, chinese academy of sciences, Beijing 100012.Center for space {2. and Applied Research Center, chinese academy of sciences, Beijing 100080 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 Center for space science and Applied Research Center Chinese Academy of Sciences Beijing 100080

Properties of the Schwabe cycles in solar activity are investigated by using wavelet transform. We study the main range of the Schwabe cycles of the solar activity recorded by relative sunspot numbers, and find that the main range of the Schwabe cycles is the periodic span from 8-year to 14-year. We make the comparison of 11-year’s phase between relative sunspot numbers and sunspot group numbers. The results show that there is some difference between two phases for the interval from 1710 to 1810, while the two phases are almost the same for the interval from 1810 to 1990.

关键词： sun sunspot sun activity method data analysis

A new DNA algorithm to solve graph coloring problem

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Progress in Natural science:Materials International 2007年第6期17卷 733-738页

作者： Jiang Xingpeng1, Li Yin2. Meng Ya3.and Meng Dazhi2.1. National Laboratory of Pattern Recognition,Institute of Automation, chinese academy of sciences, Beijing {2., china 2. College of Applied {3., Beijing University of Technology, Beijing 10002., china 3. School of science, Beijing Institute of Technology, Beijing 100081, china) National Laboratory of Pattern Recognition Institute of Automation Chinese Academy of Sciences Beijing 100080 China College of Applied sciences Beijing University of Technology Beijing 100022 China School of science Beijing Institute of Technology Beijing 100081 China

Using a small quantity of DNA molecules and little experimental time to solve complex problems successfully is a goal of DNA computing. Some NP-hard problems have been solved by DNA computing with lower time complexity than conventional computing. However, this advantage often brings higher space complexity and needs a large number of DNA encoding molecules. One example is graph coloring problem. Current DNA algorithms need exponentially increasing DNA encoding strands with the growing of problem size. Here we propose a new DNA algorithm of graph coloring problem based on the proof of four-color theorem. This algorithm has good properties of needing a relatively small number of operations in polynomial time and needing a small number of DNA encoding molecules (we need only 6R DNA encoding molecules if the number of regions in a graph is R).

关键词： DNA computing NP-hard problem graph coloring problem.