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Ionospheric Feedback Instability in the Coupling of Magnetosphere—Ionosphere

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Chinese Physics Letters 2003年第8期20卷 1401-1404页

作者：王旭宇曹晋滨 LaboratoryofSpaceWeather CenterforSpaceScienceandAppliedResearchChineseAcademyofSciencesBeijing100080 hysikalisckesInstitut UniversityofBernBernCH-3012Switzerland LaboratoryofSpaceWeather CenterforSpaceScienceandAppliedResearchChineseAcademyofSciencesBeijing100080

The ionospheric feedback instability is discussed by using the conductivity argument. We give an exact quantitative description to show that the free energy for this instability comes from the reduction of the Joule dissipation produced by the pre-existing convection electric field through self-consistent changes in ionization and conductivity due to Alfvenic perturbations in the ionosphere. By the over-reflection of Alfven waves, the energy in the active ionosphere is pumped into the magnetosphere, which is contrary to the usual case whereby energy carried by Afven waves is deposited in the ionosphere by Joule dissipation. The ionospheric feedback enhances the electron E * B drift. The electron conductivity is controlled by the ion Perdersen conductivity rather than by the electrons Pedersen conductivity. We also provide a qualitative theoretical explanation to the intense aurora favoured by a lower ambient ionospheric conductivity in the ionospheric feedback instability.

关键词： ionospheres N conductivity J(Joule) Free energy magnetospheres Feedback ionization conductivity Energy sources ionospheric conductivity Earth magnetosphere planetary magnetospheres

Neutral Barium Cloud Evolution at different Altitudes

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Chinese Physics Letters 2002年第8期19卷 1214-1216页

作者：李磊徐荣栏 centerforspacescienceandappliedresearch ChineseAcademyofSciencesPOBox8701Beijing100080

Considering the joint effects of diffusion, collision, oxidation and photoionization, we study the evolution of barium cloud at different altitude in the space plasma active experiment. The results present the variation of the loss rate, number density distribution, and brightness of the barium cloud over the range from 120 to 260 km, this can be divided into oxidation, oxidation plus photoionization and photoionization regions.

关键词： Oxidation

The O^+ Ion Flux in the Martian Magnetosphere and Martian Intrinsic Moment

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Chinese Journal of Astronomy and Astrophysics 2001年第2期1卷 185-189页

作者： Jian－KuiShi Zhen－XingLiu 等 centerforspacescienceandappliedresearch ChineseAcademyofSciencesBeijing100080 CenterforSpaceSciencea

A model is developed to study the ionospheric ion flux distribution along magnetic force lines in Martian magnetosphere and the influence of Martian intrinsic moment on the distribution. It is discovered that the intrinsic moment has significant influence on the O+ ion flux distribution that a lower flux in the magnetotail will be associated with a stronger intrinsic moment. According to the theoretical result and the observed data on the ion flux which is about 7.6 × 106 cm-2 s-1 in the Martian magnetotail, the deduced Martian moment is about 2×1021 G cm3. This agrees well with the most recent data obtained by MAG/ER on the Mars Global Surveyor spacecraft.

关键词： Planets and satellites: individual: Mars

Wavelet Analysis of Several Important Periodic Properties in the Relative Sunspot Numbers

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Chinese Journal of Astronomy and Astrophysics 2003年第5期3卷 391-394页

作者： Gui-MingLe Jia-LongWang centerforspacescienceandappliedresearch ChineseacademyofSciencesBeijing100080 NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012

We investigate the wavelet transform of yearly mean relative sunspot number series from 1700 to 2002. The curve of the global wavelet power spectrum peaks at 11-yr, 53-yr and 101-yr periods. The evolution of the amplitudes of the three periods is studied. The results show that around 1750 and 1800, the amplitude of the 53-yr period was much higher than that of the the 11-yr period, that the ca. 53-yr period was apparent only for the interval from 1725 to 1850, and was very low after 1850, that around 1750, 1800 and 1900, the amplitude of the 101-yr period was higher than that of the 11-yr period and that, from 1940 to 2000, the 11-yr period greatly dominates over the other two periods.

关键词： Sun: sunspots - Sun: activity - methods: data analysis

Verification of a Similar Cycle Prediction for the Ascending and Peak Phases of Solar Cycle 23

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Chinese Journal of Astronomy and Astrophysics 2002年第5期2卷 396-398页

作者： Jia-Long Wang Jian-Cun Gong 等 NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 centerforspacescienceandappliedresearch ChineseAcademyofSciencesBeijing100080

Reviews of long-term predictions of solar cycles have shown that a precise prediction with a lead time of 2 years or more of a solar cycle remains an unsolved problem. We used a simple method, the method of similar cycles, to make long-term predictions of not only the maximum amplitude but also the smoothed monthly mean sunspot number for every month of Solar Cycle 23. We verify and compare our prediction with the latest available observational results.

关键词： Sun: sunspots - solar-terrestrial relations

Experimental research and statistical analysis on the dielectric properties of lunar soil simulators

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Chinese Science Bulletin 2005年第10期50卷 1034-1043页

作者： LIDihui JIANGJingshan WUJi ZHANGDehai ZHANGXiaohui centerforspacescienceandappliedresearch ChineseAcademyofSciencesBeijing100080China

To support the microwave brightness data re- trieval of future China space-borne lunar exploration mi- crowave radiometer, based on the collection of plentiful ter- restrial basalts and anorthosites and their chemical composi- tions got by X-ray fluorescence, nine lunar soil simulators were prepared and made respectively into 0.8, 1.0, 1.2, 1.4 and 1.6 g/cm3 five densities each. We measured their relative dielectric constants over the range of 0.5?20 GHz with open-ended coaxial line model on the HP8722C Network Analyzer and then processed and analyzed the measurement data. This study shows that among the three parameters of density, frequency and composition, density has the strongest effect on the relative dielectric constants, frequency comes second, composition the least. The three parameters account for 45%, 33% and 22% respectively of the changed real part of a relative dielectric constant, and 55%, 27% and 19% respectively of the changed imaginary part. The real parts of the relative dielectric constants are linearly linearly corre- lated with density or frequency, and the imaginary parts have a linear relation with both approximately over the range of 0.5?10 GHz and tend to be poorly correlated with them in 10?20 GHz. The effect of composition on a relative dielectric constant seems very complicated, both probably do not follow a simple function relation, with the least correla- tion. Multiple regression analysis indicates that major ele- ment oxides SiO2, Al2O3, CaO, MgO, TiO2 and ?Fe are cor- respondent to a one-order polynomial, and TiO2 or ?Fe or TiO2+?Fe has not been proven to be the indicators in the contribution to the relative dielectric constants.

关键词：月球土壤模拟探测技术绝缘体玄武岩

Excitation of Electromagnetic Waves by an Electron Ring Beam in a Magnetized Plasma Waveguide

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Chinese Physics Letters 2002年第10期19卷 1556-1559页

作者：周国成吴京生等 centerforspacescienceandappliedresearch ChineseAcademyofSciencesBeijing100080 DepartmentofEarthandSpaceSciences UniversityofScienceandTechnologyofCHinaHefei230026

We study the resonant interactions between an electron ring beam and plasma waveguide modes. This is motivated by the research ofradio emission in low solar corona. We consider a density-depleted duct (above an active region near a flare site) that may be treated as amagnetized plasma waveguide. The electromagnetic waves excited in the waveguide are classified into the so-calledE-type andB-type waves. The results show that there are two unstable modes ofB-type waves propagating parallel and anti-parallel to the direction of theelectron beam. The effect of the finite radius and boundary conditions of the waveguide on the excitation of waveguide modes isimportant. For a givenB-type mode, the smaller the radiusR, the larger the temporal and spatial amplification rate. We suggest thatthese excited waveguide modes could be one of the processes responsible for the observed solar radio emission.

关键词： Circular waveguides

A Quasi—One—Dimensional Model for a Solar Flux Tube

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Chinese Physics Letters 2002年第8期19卷 1217-1220页

作者：杨志良冯学尚等 SolarPhysics BeijingAstronomicalObservatoryBeijing100012 SpaceWeatherLaboratory CenterforSpaceScienceandAppliedResearchChineseAcademyofSciencesBeijing100080

We develop the quasi-one-dimensional flux tube model with magnetohydrodynamical equations. In order to know whether themagnetic field can maintain their similar structure from photosphere to chromosphere, we suppose that the flux tube is thin inradius relative to the length, and that the quantities in the cross section are averaged. The radii of the flux tube and the magnetic field arenumerically simulated. One of the important results shows that the flux tube does not expand as quickly as the existing model when it is out ofthe photosphere with high velocity. This is consistent with observations of the magnetic field in the photosphere andchromosphere.

关键词： Magnetic fields Chromosphere Solar models

Plasma structures inside boundary layers of magnetic clouds

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Chinese Science Bulletin 2004年第23期49卷 2533-2537页

作者： WEIFengsi FENGXueshang YANGFang ZHONGDingkun SIGMAWeatherGroup LaboratoryforSpaceWeatherCenterforSpaceScienceandAppliedResearchChineseAcademyofSciencesBeijing100080China

We analyze the plasma structures for 50 mag- netic cloud boundary layers (BLs) which were observed by the spacecraft WIND from February, 1995 to June 2003. Main discoveries are: (ⅰ) The BL is a non-pressure balanced structure, its total pressure, PT,L, (the thermal pressure, Pth,L, plus the magnetic pressure, PM,L) is generally less than the total pressure PT,S and PT,C of the front solar wind (SW) and the following magnetic clouds (MC), respectively. The rising of the Pth,L inside the BLs is often not enough to compensate the declining of PM,L; (ⅱ) The ratio of electron and proton temperatures, (Te/Tp)L, inside the BLs is offen less than (Te/Tp)s and (Te/Tp)c in the SW and the MC, respectively, be- cause the heating of proton is more obvious than that of elec- tron; and (ⅲ) The reversal jet is observed in 80% BLs inves- tigated, in which the reversal jets from all of three directions (±Vx, ±Vy, ±Vz), were observed in ≈25% BLs. These basic characteristics could be associated with a possible magnetic reconnection process inside the BLs. The results above suggest that the cloud BL owns the plasma structures different from those in the SW and MC. It is a manifestation for the existing significant dynamic interaction between the magnetic cloud and the solar wind.

关键词：等离子体结构分析磁云分界层平衡结构温度太阳风