2003 Vol. 23, No. 5
2003, 23(5): 321-328.
Abstract:
Solar flares are believed to result from the sudden release of energy stored in magnetic field. In this paper the X-ray solar flares with importance greater than and equal to M1.0 occurred from 1996 to 2002 on the South and North of the solar disk are investigated. The results show that the intensity of the solar flare activities occurred in the Northern and Southern hemisphere is different. As a whole, the solar flare activities in north hemisphere are more intense than that in the south hemisphere during the interval form 1996 to July 2001, while the situation is contrary from August 2001 to 2002. The period of the most intense solar activities for Solar Cycles 23 is July 2000. The solar flare activities in November 1999, March 2000, March and April 2001, September to December 2001 and July to August 2002 are also very intensive. The solar flare index for the interval from 1996-2001 is also investigated. The result shows that the value of solar flare index of the north hemisphere in July 2000 has the biggest value and very outstanding which means that the solar activities in July 2000 are the most intensive for Solar Cycle 23. This result is consistent with that the monthly sunspot numbers having the bigges value in July 2000 for Solar Cycle 23. Because the biggest value of the smoothed monthly mean sunspot number in Solar Cycle 23 is 120.4 in April 2000, so the monthly mean sunspot numbers can depict the solar activity better than smoothed monthly mean sunspot numbers. Now we can’t judge which hemisphere’s solar flare activities are more intensive, we will get the answer till the end of the Solar Cycle 23. If we want to really compare the solar activities for Solar Cycle 23 between the two hemispheres, the whole areas of the sunspot, coronal mass ejections, and solar proton events and so on must be compared between two hemispheres.
Solar flares are believed to result from the sudden release of energy stored in magnetic field. In this paper the X-ray solar flares with importance greater than and equal to M1.0 occurred from 1996 to 2002 on the South and North of the solar disk are investigated. The results show that the intensity of the solar flare activities occurred in the Northern and Southern hemisphere is different. As a whole, the solar flare activities in north hemisphere are more intense than that in the south hemisphere during the interval form 1996 to July 2001, while the situation is contrary from August 2001 to 2002. The period of the most intense solar activities for Solar Cycles 23 is July 2000. The solar flare activities in November 1999, March 2000, March and April 2001, September to December 2001 and July to August 2002 are also very intensive. The solar flare index for the interval from 1996-2001 is also investigated. The result shows that the value of solar flare index of the north hemisphere in July 2000 has the biggest value and very outstanding which means that the solar activities in July 2000 are the most intensive for Solar Cycle 23. This result is consistent with that the monthly sunspot numbers having the bigges value in July 2000 for Solar Cycle 23. Because the biggest value of the smoothed monthly mean sunspot number in Solar Cycle 23 is 120.4 in April 2000, so the monthly mean sunspot numbers can depict the solar activity better than smoothed monthly mean sunspot numbers. Now we can’t judge which hemisphere’s solar flare activities are more intensive, we will get the answer till the end of the Solar Cycle 23. If we want to really compare the solar activities for Solar Cycle 23 between the two hemispheres, the whole areas of the sunspot, coronal mass ejections, and solar proton events and so on must be compared between two hemispheres.
2003, 23(5): 329-333.
Abstract:
The comets are consisted mainly of water and dust and around cometary nuclear there are ionized gases mainly made up of water and hydrogen. Dust grains in comet will become charged. As a new composition, charged dust grains will take part in cometary plasma group behaviors. Three main charging mechanisms are considered in this paper. First, charged plasma particles spray onto surfaces of dust grains will be collected, this current is presented by J1; second, photoemission caused by the solar rays, the photoelectron current is J2; third, J3, current of secondary electron eject. At a certain stage, dust grains will stop charging and attain an equilibrium-state, i.e., ∑ Jα = 0, α = 1,2,3. Considering that comets are plasma environments of H2O+, and the main compositions of cometary dust are silicate and carbon, based upon observational data of comet Halley and comet G-Z, the charging characteristics and equilibrium potentials of dust grains are calculated. A curve of equilibrium potential at different distance from the nuclear of P/Halley is provided. It is found that the equilibrium potential is obviously correlative with electron density. Using algebraic equations about equilibrium potential and logarithm of electron density, too, the calculations showed that the equilibrium potential has little relativity with other plasma parameters such as electron temperature. Generally, these conclusions can be suitable for other plasma comets.
The comets are consisted mainly of water and dust and around cometary nuclear there are ionized gases mainly made up of water and hydrogen. Dust grains in comet will become charged. As a new composition, charged dust grains will take part in cometary plasma group behaviors. Three main charging mechanisms are considered in this paper. First, charged plasma particles spray onto surfaces of dust grains will be collected, this current is presented by J1; second, photoemission caused by the solar rays, the photoelectron current is J2; third, J3, current of secondary electron eject. At a certain stage, dust grains will stop charging and attain an equilibrium-state, i.e., ∑ Jα = 0, α = 1,2,3. Considering that comets are plasma environments of H2O+, and the main compositions of cometary dust are silicate and carbon, based upon observational data of comet Halley and comet G-Z, the charging characteristics and equilibrium potentials of dust grains are calculated. A curve of equilibrium potential at different distance from the nuclear of P/Halley is provided. It is found that the equilibrium potential is obviously correlative with electron density. Using algebraic equations about equilibrium potential and logarithm of electron density, too, the calculations showed that the equilibrium potential has little relativity with other plasma parameters such as electron temperature. Generally, these conclusions can be suitable for other plasma comets.
2003, 23(5): 334-342.
Abstract:
In this paper, the behavior of the electron density between the height of 66 and 80km observed by MF radar at Waknnai station （45.36°N, 141.81°E） during four X-class flares is studied. The sudden increase of the electron density is observed during all of the flare period. The results show that the MF radar can be used as one routine method to observe electron density of the ionospheric D region. By comparison with the soft X-ray flux, it is found that the temporal variation of the electron density in the lower D region has a good correlation with the soft X-ray flux observed by GOES. Nevertheless, the correlation is not good in the higher altitude because of the atmospheric disturbances in the D region. On the other hand, the increases of electron density depends on the parameters of these four flares, the increase of the electron density for some of flare reach as high as 400 cm-3, some of them is only about 100cm-3. Compared with the increase of the total electron content （TEC） caused by the flare with similar parameters, the total increase of electron density between the height of 66 and 80 km is only about one thousandth of TEC that almost has no effect on the delay time of the radiowave. But, the effect of the Sudden Ionospheric Disturbances caused by the increase of the electron density is very strong due to the very high number density of the atmospheric neutral compositions in the height of D region. In the end, the effective recombination coefficient at different heights is estimated using the electron density at the recovery period during the flare on Nov. 4, 1997.
In this paper, the behavior of the electron density between the height of 66 and 80km observed by MF radar at Waknnai station （45.36°N, 141.81°E） during four X-class flares is studied. The sudden increase of the electron density is observed during all of the flare period. The results show that the MF radar can be used as one routine method to observe electron density of the ionospheric D region. By comparison with the soft X-ray flux, it is found that the temporal variation of the electron density in the lower D region has a good correlation with the soft X-ray flux observed by GOES. Nevertheless, the correlation is not good in the higher altitude because of the atmospheric disturbances in the D region. On the other hand, the increases of electron density depends on the parameters of these four flares, the increase of the electron density for some of flare reach as high as 400 cm-3, some of them is only about 100cm-3. Compared with the increase of the total electron content （TEC） caused by the flare with similar parameters, the total increase of electron density between the height of 66 and 80 km is only about one thousandth of TEC that almost has no effect on the delay time of the radiowave. But, the effect of the Sudden Ionospheric Disturbances caused by the increase of the electron density is very strong due to the very high number density of the atmospheric neutral compositions in the height of D region. In the end, the effective recombination coefficient at different heights is estimated using the electron density at the recovery period during the flare on Nov. 4, 1997.
2003, 23(5): 343-351.
Abstract:
Using momentum equation, energy equation and continuity equation of electrons in the upper ionosphere, with the assumption of ambipolar diffusion and β combination of electrons, a theoretical model for heating of the upper ionosphere by powerful high-frequency radio waves is presented. In this paper, these equations are solved numerically to calculate the change of the electron temperature and density at the heights between 150km and 400km in the ionosphere. For specific transmitter’s parameters and specific radio waves energy absorbed model, the calculated results show that the perturbation of the electron temperature and density are obvious. In terms of the selected parameters in this paper, the calculated results show that the electron temperature is increased by about 10%-25%, and the electron density is decreased by 1%-2% or so in the vicinity of the reflective point of radio waves. The time scales of electron temperature to reach its steady state is much faster than that of electron density. Finally, by means of these results, some observed phenomena in many heating experiments are explained in this paper.
Using momentum equation, energy equation and continuity equation of electrons in the upper ionosphere, with the assumption of ambipolar diffusion and β combination of electrons, a theoretical model for heating of the upper ionosphere by powerful high-frequency radio waves is presented. In this paper, these equations are solved numerically to calculate the change of the electron temperature and density at the heights between 150km and 400km in the ionosphere. For specific transmitter’s parameters and specific radio waves energy absorbed model, the calculated results show that the perturbation of the electron temperature and density are obvious. In terms of the selected parameters in this paper, the calculated results show that the electron temperature is increased by about 10%-25%, and the electron density is decreased by 1%-2% or so in the vicinity of the reflective point of radio waves. The time scales of electron temperature to reach its steady state is much faster than that of electron density. Finally, by means of these results, some observed phenomena in many heating experiments are explained in this paper.
2003, 23(5): 352-360.
Abstract:
By comparing the modeled results with observations obtained by Wuhan University Lidar, the validity of the current Na layer model is examined. With a small number of permitted adjustable parameters, the model is able to reproduce many observed features of the Na layer remarkably well. The stability of a simplified model is analyzed by using the perturbation method. It is indicated that the model is a stable system because all the model’s five eigenvalues’ real parts are negative when reasonably adjusting the mayor coefficients, including the wavelengths of perturbations, the concentration of the background chemical species, eddy coefficient, and temperature. The results show that the wavelengths of perturbations and the magnitude of eddy coefficient strongly influence all the five eigenvalues: the magnitudes of all the eigenvalues’ real parts ascend with the increasing perturbation wavelengths and descend with the increasing eddy coefficient. However, the concentrations of the background clemical species and temperature have strong effects on only part of them.
By comparing the modeled results with observations obtained by Wuhan University Lidar, the validity of the current Na layer model is examined. With a small number of permitted adjustable parameters, the model is able to reproduce many observed features of the Na layer remarkably well. The stability of a simplified model is analyzed by using the perturbation method. It is indicated that the model is a stable system because all the model’s five eigenvalues’ real parts are negative when reasonably adjusting the mayor coefficients, including the wavelengths of perturbations, the concentration of the background chemical species, eddy coefficient, and temperature. The results show that the wavelengths of perturbations and the magnitude of eddy coefficient strongly influence all the five eigenvalues: the magnitudes of all the eigenvalues’ real parts ascend with the increasing perturbation wavelengths and descend with the increasing eddy coefficient. However, the concentrations of the background clemical species and temperature have strong effects on only part of them.
2003, 23(5): 361-370.
Abstract:
An all-sky meteor radar was set up in January 2002 in Wuhan and it is the first meteor radar in China. The characteristics of diurnal and semidiurnal tides over Wuhan from February 19 to July 31 are discussed in this paper. The main tidal component is diurnal tide which is much greater than the semidiurnal tide, and the sources of both tide components are below 80km. The diurnal tidal components reach their maximum in February and March, and the meridional components are stronger than the zonal components. Zonal and meridional diurnal tides reach their maximum of 44 m/s and 60 m/s at about 95 km, respectively. The semidiurnal tide reaches its maximun amplitude 24 m/s at about 93 km at the beginning of April. The amplitudes and phases of diurnal and semidiurnal tides show some quasi-periodic characteristics which may be resulted from nonlinear interaction between tides and planetary waves. The comparison of the observed tide and GSWM values shows that the variation of both diurnal and semidiurnal tidal phase with height is agreement. But the diurnal tidal phases of the GSWM are 1-2 hours ahead of the observed phases and the semidiurnal tidal phases of the GSWM are 1-4 hours lag of the observed phases. There are significant difference between GSWM tidal amplitudes and the observed amplitudes while the tides are strong. And the observed tidal amplitudes have maximum values at about 95km, but GSWM values have not maximum from 80 to 100km. The observed amplitudes of semidiurnal tide are generally greater than the GSWM amplitudes, as much as twise greater in some months.
An all-sky meteor radar was set up in January 2002 in Wuhan and it is the first meteor radar in China. The characteristics of diurnal and semidiurnal tides over Wuhan from February 19 to July 31 are discussed in this paper. The main tidal component is diurnal tide which is much greater than the semidiurnal tide, and the sources of both tide components are below 80km. The diurnal tidal components reach their maximum in February and March, and the meridional components are stronger than the zonal components. Zonal and meridional diurnal tides reach their maximum of 44 m/s and 60 m/s at about 95 km, respectively. The semidiurnal tide reaches its maximun amplitude 24 m/s at about 93 km at the beginning of April. The amplitudes and phases of diurnal and semidiurnal tides show some quasi-periodic characteristics which may be resulted from nonlinear interaction between tides and planetary waves. The comparison of the observed tide and GSWM values shows that the variation of both diurnal and semidiurnal tidal phase with height is agreement. But the diurnal tidal phases of the GSWM are 1-2 hours ahead of the observed phases and the semidiurnal tidal phases of the GSWM are 1-4 hours lag of the observed phases. There are significant difference between GSWM tidal amplitudes and the observed amplitudes while the tides are strong. And the observed tidal amplitudes have maximum values at about 95km, but GSWM values have not maximum from 80 to 100km. The observed amplitudes of semidiurnal tide are generally greater than the GSWM amplitudes, as much as twise greater in some months.
2003, 23(5): 371-378.
Abstract:
The present paper deals with both the computer simulation and statistical study of sporadic E-layers at mid-latitude regions. According to the widely accepted wind shear theory, simulation for the formation of Es under the action of wind fields and electric fields was carried out. The simulation work is based on the continuity equation and momentum equation and method of characteristics curve is adopted. We accomplish simulating the convergence of metal ions to form a thin layer under reasonable dynamics conditions. The wind field data come from the HWM93 empirical model and the electric field data from the drift empirical model. The results of simulation confirm the validity of the wind shear theory indirectly. When changing the input parameter of the HWM93 empirical model and the drift empirical model, we obtained different results, which make it possible for us to study the reaction of Es peak density on the diurnal and seasonal variations of the background dynamics conditions. The results agree with the statistical temporal variation feature of the sporadic E occurrence. After a comparison of data statistic results, the reliable part of the theory is confirmed and its irrationality is discussed.
The present paper deals with both the computer simulation and statistical study of sporadic E-layers at mid-latitude regions. According to the widely accepted wind shear theory, simulation for the formation of Es under the action of wind fields and electric fields was carried out. The simulation work is based on the continuity equation and momentum equation and method of characteristics curve is adopted. We accomplish simulating the convergence of metal ions to form a thin layer under reasonable dynamics conditions. The wind field data come from the HWM93 empirical model and the electric field data from the drift empirical model. The results of simulation confirm the validity of the wind shear theory indirectly. When changing the input parameter of the HWM93 empirical model and the drift empirical model, we obtained different results, which make it possible for us to study the reaction of Es peak density on the diurnal and seasonal variations of the background dynamics conditions. The results agree with the statistical temporal variation feature of the sporadic E occurrence. After a comparison of data statistic results, the reliable part of the theory is confirmed and its irrationality is discussed.
2003, 23(5): 379-387.
Abstract:
The operation frequency band of microwave radiometer on SZ-4 spaceship is located up to millimeter wave, This is hither to unprecedented in development of our spacecraft antennas. By means of computer aided integrated method for mechanical, electrical and thermal design, beginning with choice of materials the optimal design on electro-and structure has been combined with manufacture and assembly technology effectively to guarantee the minimum deformation of the reflector. This paper describes controlling and realization of high accuracy of reflector shape.
The operation frequency band of microwave radiometer on SZ-4 spaceship is located up to millimeter wave, This is hither to unprecedented in development of our spacecraft antennas. By means of computer aided integrated method for mechanical, electrical and thermal design, beginning with choice of materials the optimal design on electro-and structure has been combined with manufacture and assembly technology effectively to guarantee the minimum deformation of the reflector. This paper describes controlling and realization of high accuracy of reflector shape.
2003, 23(5): 388-395.
Abstract:
Double-Star positioning system is one kind of regional satellite positioning system built up in China, it’s aim is to provide more accurate position information for the user, but it’s shortcoming is that the real-time positioning is dufficulty to get. It is one new concept to use the Double-Star positioning system to measure the attitude. This paper introduces one kind of the basic principles of attitude determination with Double-Star positioning system on the basis of the satellite simulator and gives the mathematic model of the attitude measurement. Thus the shortcoming mentioned above can be overcome. When the position and attitude information of Double-Star positioning system and strap-down inertial system are integrated, the state and measurement functions are built up, the simulation is made under specific orbit. The simulation results show that the system’s accuracy can be improved effectively.
Double-Star positioning system is one kind of regional satellite positioning system built up in China, it’s aim is to provide more accurate position information for the user, but it’s shortcoming is that the real-time positioning is dufficulty to get. It is one new concept to use the Double-Star positioning system to measure the attitude. This paper introduces one kind of the basic principles of attitude determination with Double-Star positioning system on the basis of the satellite simulator and gives the mathematic model of the attitude measurement. Thus the shortcoming mentioned above can be overcome. When the position and attitude information of Double-Star positioning system and strap-down inertial system are integrated, the state and measurement functions are built up, the simulation is made under specific orbit. The simulation results show that the system’s accuracy can be improved effectively.
2003, 23(5): 396-400.
Abstract:
Natural space radiation such as that found in the Van Allen belts （electrons and protons） inflicts ionizing dose damage on semiconductor devices. This damage degrades the performance of many types of semiconductor. Consequently, the life of important military and commercial missions is shortened. A simple and direct way to lengthen the life of semiconductor is to shield them against the energetic radiation particle environment. Electrons and protons can be shielded effectively, while energetic heavy ions and gamma radiation are difficult to shield. The secondary package technique of compositing material of 54HCT00 CMOS device is adopted and experimental circuit of device is designed in this paper. Devices on bias are irradiated by electron source and results are obtained with the help of measurement on line. The level of ionizing dose is increased by 1-2 order of magnitude using secondary package. The anticipated data and results are achieved. An approach is provided to exploit space application for commercial semiconductor device.
Natural space radiation such as that found in the Van Allen belts （electrons and protons） inflicts ionizing dose damage on semiconductor devices. This damage degrades the performance of many types of semiconductor. Consequently, the life of important military and commercial missions is shortened. A simple and direct way to lengthen the life of semiconductor is to shield them against the energetic radiation particle environment. Electrons and protons can be shielded effectively, while energetic heavy ions and gamma radiation are difficult to shield. The secondary package technique of compositing material of 54HCT00 CMOS device is adopted and experimental circuit of device is designed in this paper. Devices on bias are irradiated by electron source and results are obtained with the help of measurement on line. The level of ionizing dose is increased by 1-2 order of magnitude using secondary package. The anticipated data and results are achieved. An approach is provided to exploit space application for commercial semiconductor device.
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Publisher：Science Press
ISSN：ISSN 0254-6124
CN：CN 11-1783/V
Editor chief：WU Ji
Counselor：Gu YiDong
Deputy-chief-editor：
CAO Jinbin
FALANGA Maurizio (Switzerland)
FU Suiyan KANG Qi
LIN Baojun LIN Yangting
SHI Jiancheng YANG Huigen
YANG Zhen ZHANG Shuangnan
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