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1.
"嫦娥"一号、二号绕月飞行经历地球磁尾边界层区域时,分别在2007年11月26日—2008年2月5日和2010年10月3日—2011年2月28日,发现了15次月球轨道0.1~2 MeV电子急剧增加(Bursts of 0.1~2 MeV Energetic Electrons,BEE),卫星周围等离子体离子加速的现象.统计研究表明,这类现象发生在稳定太阳风和弱行星际磁场条件下,且无显著空间环境扰动事件发生时,离子的加速滞后于高能电子爆发,离子能量的变化与高能电子通量的时间演化正相关,地球磁鞘内侧或边界层过渡区域是该类现象的高发区,离子能量增加时卫星表面电位大幅下降可达负几千伏.为了研究高能电子爆发与绕月卫星表面电位变化的关系及其对月球表面电位的影响,本文用电流平衡法建立绕月卫星和月球表面充电模型,并假设能量电子(2eV~2 MeV)满足幂律谱的分布,模拟急剧增加的能量电子对卫星和月球表面电位的影响.模拟结果表明,能量电子急剧增加使得绕月卫星和月球表面电位大幅下降;能量电子总流量1011 cm-2时,绕月卫星和月球表面充电电位可达负上千伏;月球充电到大的负电位的时间仅为卫星充电时间的1/10.鉴于高能电子急剧增加事件的高发生率(~125次/年),能量电子急剧增加使得绕月卫星表面电位大幅下降的发生率应大于实测等离子体离子加速现象的发生率(~25次/年).  相似文献   

2.
利用大约15个月的CRRES卫星MEA能量电子观测数据,分别在地磁活动平静(0≤Kp＜3)、中等(3≤Kp≤6)及强烈(6＜Kp≤9)的条件下,选取电子能量为148 keV,509 keV,1090 keV,1581 keV的辐射带能量电子通量进行统计分析,得到了不同地磁活动条件下地球辐射带高能电子通量在(L,MLT)...  相似文献   

3.
本文根据ＬＥＯ中等离子体温度低，密度高，德拜长度小的特点，采用薄鞘层近似，计算了离子收集电流；根据电流平衡方程，考虑表面二次电子发射，计算了大型航天器表面在沉降电子流辐照下的充电特性。  相似文献   

4.
The magnetotail lobes are two vast regions between the plasma sheet (PS) and the magnetotail boundary layers at the magnetopause, where the plasma has very low temperature and densities. The open magnetic field lines of the lobes directly couple the ionospheric polar caps with the solar wind (SW) through the magnetosheath. The survey of 576 h INTERBALL-1 measurements in the near (XGSM>−27RE) lobes in October–November 1997 shows that they are populated with plasmas of various origin and properties. Presented and discussed in details are four cases of lobe measurements under different geomagnetic conditions. Discrete plasma structures encountered in the lobes could originate from the PS, from the magnetosheath or the mantle. A ubiquitous picture in the lobes is the registration of ‘clouds’ of anisotropic electrons with energies up to 300–500 eV, with no accompanying ions. The electron distributions are highly variable and complex, with different degree of anisotropy. The earthward flowing electrons originate in the SW, the anisotropy of the electron fluxes reflects the anisotropy of the SW electrons. In some cases the tailward electrons are not only mirrored earthward fluxes but an additional source earthward of the observations is present. The positive spacecraft potential plays a substantial role in modifying the observed electron distributions.  相似文献   

5.
The relation of the Kp index of geomagnetic activity to the solar wind electric field (E SW) and the projection of this field onto the geomagnetic dipole has been estimated. An analysis indicated that the southward component of the IMF vector (B z < 0) is the main geoeffective parameter, as was repeatedly indicated by many researchers. The presence of this component in any combinations of the interplanetary medium parameters is responsible for a high correlation between such combinations and geomagnetic activity referred to by the authors of different studies. Precisely this field component also plays the main role in the relation between the Kp index and the relative orientation of E SW and the Earth’ magnetic moment.  相似文献   

6.
Using the foF2 database obtained from satellites and ground-based ionospheric stations, we have constructed a global empirical model of the critical frequency of the ionospheric F2-layer (SDMF2—Satellite and Digisonde Data Model of the F2 layer) for quiet geomagnetic conditions (Kp < 3). The input parameters of this model are the geographical coordinates, UT, day, month, year, and the integral index F10.7 (day, τ = 0.96) of solar activity for a given day. The SDMF2 model was based on the Legendre method for the spatial expansion of foF2 monthly medians to 12 in latitude and 8 in longitude of spherical harmonics. The resulting spatial coefficients have been expanded by the Fourier method in three spherical harmonics with respect to UT. The effect of the saturation of critical frequency of the ionospheric F2-layer at high solar activity was described in the SDMF2 model by foF2 as a logarithmic function of F10.7 (day, τ = 0.96). The difference between the SDMF2 and IRI models is a maximum at low solar activity as well as in the Southern Hemisphere and in the oceans. The testing on the basis of ground-based and satellite data has indicated that the SDMF2 model is more accurate than the IRI model.  相似文献   

7.
We present Prognoz-8 observations of low-frequency plasma waves (2-105 Hz) associated with plasma fluxes near the outer boundary of the plasma sheet. These plasma fluxes were different from the regular plasma sheet boundary layer and consisted of tailward flowing warm proton and cold oxygen beams accompanied by rather cold electrons (T e less than 100 eV). Observed plasma characteristics were used in the numerical solution of the dispersion relation for the ion-beam acoustic instability. Detailed analysis shows that this instability can be a source of observed emissions at frequencies up to 25 Hz.  相似文献   

8.
By analyzing the variations of global electron content (GEC) during geomagnetic storm events, the ratio “GEC/GECQT” is found to be closely correlated with geomagnetic Kp index and time weighted Dst index, where GECQT is the quiet time reference value. Moreover, the GEC/GECQT will decrease with the increase of the solar flux F10.7 index. Furthermore, we construct a linear model for storm-time response of GEC. Eighty-two storm events during 1999–2011 were utilized to calculate the model coefficients, and the performance of the model was tested using data of 8 storm events in 2012 by comparing the outputs of the model with the observed GEC values. Results suggest that the model can capture the characteristics of the GEC variation in response to magnetic storms. The component describing the solar activity influence shows a counteracting effect with the geomagnetic activity component; and the influence of Kp index causes an increase of GEC, while the time weighted Dst index causes a decrease of GEC.  相似文献   

9.
李程  陈东 《地球物理学报》2019,62(6):1991-2000
高能电子穿透航天器并在其内部沉积电荷从而引发深层充电效应,是导致卫星故障的重要因素之一.为了评估深层充电效应诱发卫星异常的风险,本文基于贝叶斯方法,使用一颗地球同步轨道卫星的异常数据和GOES-8卫星的电子通量探测数据,计算了不同能量阈值及累积时间的电子注量、不同卫星配置下模拟仿真的沉积电荷,并分别与卫星异常建立一系列概率风险模型.本文从模型中随机抽样得到模拟异常,并与实测异常构造混淆矩阵以评估模型拟合优度,结果表明1.0MeV电子3日累积注量-卫星异常概率风险模型为该卫星最优模型.本文利用最优模型对该卫星深层充电效应风险进行了计算,在1.0MeV电子3日累积注量达到2.0×10~(10)cm~(-2)·sr~(-1)时,该卫星发生深层充电异常的平均后验概率为27%,且95%最小可信值为22%.根据最优模型,我们对该卫星最可能导致异常的部件的材料和结构等特征做出了推断.  相似文献   

10.
The transport of water through the sediments of Lake Kinneret was estimated using tritium of fallout origin as a tracer. The calculation model takes into account the diffusion of the tracer and its decay, and allows for the advective flux through the sediment pores as a free parameter. The dependence of the interstitial diffusion constant on the porosity was assumed identical to that for chloride ions. Tritium profiles in nine cores were used for estimating the advective fluxes and velocities, by finding the best fit between data and model. Water advective fluxes of 3.4 g cm?2 yr?1 into the lake were found. This water flux is negligible in the hydrological balance of Lake Kinneret; but it carries along 7% of the unaccounted-for chloride input to the lake.  相似文献   

11.
The suggestion that the polar cap can completely disappear under certain northward IMF conditions is still controversial. We know that the size of the polar cap is strongly controlled by the interplanetary magnetic field (IMF). Under a southward IMF, the polar cap is usually large and filled with weak diffuse polar rain electrons. The polar cap shrinks under a northward IMF. Here we use the global auroral images and coincident particle measurements on May 15, 2005 to show that the discrete arcs (due to precipitation of both electrons and ions) expanded from the dayside oval to the nightside oval and filled the whole polar ionosphere after a long (8 h) and strong (～5–30 nT) northward IMF Bz, The observations suggested that the polar cap disappeared under a closed magnetosphere.  相似文献   

12.
We have analyzed the onsets of energetic particle bursts detected by the ICS and STICS sensors of the EPIC instrument on board the GEOTAIL spacecraft in the deep magnetotail (i.e., at distances greater than 180 RK). Such bursts are commonly observed at the plasma-sheet boundary layer (PSBL) and are highly collimated along the magnetic field. The bursts display a normal velocity dispersion (i.e., the higher-speed particles are seen first, while the progressively lower speed particles are seen later) when observed upon entry of the spacecraft from the magnetotail lobes into the plasma sheet. Upon exit from the plasma sheet a reverse velocity dispersion is observed (i.e., lower-speed particles disappear first and higher-speed particles disappear last). Three major findings are as follows. First, the tailward-jetting energetic particle populations of the distant-tail plasma sheet display an energy layering: the energetic electrons stream along open PSBL field lines with peak fluxes at the lobes. Energetic protons occupy the next layer, and as the spacecraft moves towards the neutral sheet progressively decreasing energies are encountered systematically. These plasma-sheet layers display spatial symmetry, with the plane of symmetry the neutral sheet. Second, if we consider the same energy level of energetic particles, then the H layer is confined within that of the energetic electron, the He++ layer is confined within that of the proton, and the oxygen layer is confined within the alpha particle layer. Third, whenever the energetic electrons show higher fluxes inside the plasma sheet as compared to those at the boundary layer, their angular distribution is isotropic irrespective of the Earthward or tailward character of fluxes, suggesting a closed field line topology.  相似文献   

13.
Rhythms of heliogeomagnetic activity and their dynamics in the solar activity (SA) cycles are analyzed. Heliogeomagnetic rhythms are the mixture of a periodic signal and noise component, which differs from a periodic signal by a substantial suddenness. Therefore, the filtering methods optimized for smoothness were used to analyze these rhythms and to separate rhythm periodic components. Short-period rhythms of the Kp index of geomagnetic activity and Wolf numbers (W) have been revealed. The rhythm dynamics in SA cycles has been indicated. Clearly defined near-seven-day, semi-seven-day, and other components, which are harmonics of the solar rotation period, are present in the rhythms of the Kp index in contrast to W. A comparison of the Kp and Dst rhythms indicates that the seasonal and annual variations in these indices are substantially similar. It has been indicated that the rhythms of heliogeomagnetic activity could be the external synchronizers of biological rhythms, having integrated into the endogenous temporal structure of these rhythms in the process of evolution, and that the dependence of the population macroparameters on W is much weaker than on Kp.  相似文献   

14.
A planetary pattern of substorm development in auroral precipitation has been constructed on the basis of the F6 and F7 satellite observations. The behavior of the auroral injection boundaries and characteristics of precipitating electrons in various precipitation regions during all phases of a statistically mean magnetospheric substorm with an intensity of AL ～ ?400 nT at a maximum is considered in detail. It is shown that during a substorm, the zone of structured auroral oval precipitation AOP and the diffuse auroral zone DAZ are the widest in the nighttime and daytime sectors, respectively. In the daytime sector, all precipitation regions synchronously shift equatorward not only at the origination phase but during the substorm development phase. The strongest shift to low latitudes of the daytime AOP region is observed at a maximum of the development phase. As a result of this shift, the area of the polar cap increases during the phases of substorm origination and development. It is shown that the average position of the precipitation boundaries and the energy fluxes of precipitating electrons at each phase are linearly related to the intensity of a magnetic disturbance. This makes it possible to develop a model of auroral precipitation development during each phase of substorms of any intensity.  相似文献   

15.
We investigate the flux evolution of geostationary orbit energetic electrons during a strong storm on 24 August 2005(event A,the storm index Dst<200 nT,the average substorm index AE=436 nT)and a weak storm on 28 October 2006(event B,Dst>50 nT,average AE=320 nT).Data collected by LANL and GOES-12 satellites show that energetic electron fluxes increase by a factor of 10 during the recovery phase compared to the prestorm level for both events A and B.As the substorm continued,the Cluster C4 satellite observed strong whistler-mode chorus waves(with spectral density approaching 10 5nT2/Hz).The wave amplitude correlates with the substorm AE index,but is less correlated with the storm Dst index.Using a Gaussian distribution fitting method,we solve the Fokker-Planck diffusion equation governing the wave-particle interaction.Numerical results demonstrate that chorus waves efficiently accelerate~1 MeV energetic electrons,particularly at high pitch angles.The calculated acceleration time scale and amplitude are comparable to observations.Our results provide new observational support for chorus-driven acceleration of radiation belt energetic electrons.  相似文献   

16.
The study aims to calibrate/validate and apply the dune-erosion model, XBeach, in order to predict morphological response to storm events along a meso-tidal, steeply sloping beach. More than 10,000 XBeach calibration runs, including different model parameters and erosion events, were compared with measurements of beach-profile response to storm conditions. Off-shore wave and tidal measurements were used as input for a SWAN wave model, which was used to provide wave conditions to XBeach. The results indicate that using XBeach to predict beach-profile morphodynamic response during storm events on steeply sloping intermediate-to-reflective beaches may be more demanding than for dissipative beaches and that the default model setup can overestimate dune/beach-face erosion. The performance of the model after calibration was satisfactory, with Brier Skill Scores from 0.2 to 0.72. XBeach was found to be more sensitive to input parameters such as the beach-face slope and the surf similarity parameter ξ (especially for values ξ?>?0.6). The calibrated XBeach setup was used for simulations of storm scenarios with different return periods (5, 25, and 50?years), and the simulations highlighted the fragility of the dune field and the potential for storm-induced dune retreat, lowering, and overwash in the study area. Finally, the nested SWAN/XBeach models were forced by an existing operational wave-forecast WAVEWATCH-III/SWAN model, operated by the Portuguese Hydrographic Institute to generate daily forecasts of storm impact and serve as a prototype-case for an early warning system for storm hazard mitigation.  相似文献   

17.
Increases in solar protons and variations in the electron and proton fluxes from the outer radiation belt are studied based on the GLONASS satellite measurements (the circular orbit at an altitude of ～20000 km with an inclination of ～65°) performed in December 2006. Indications in the channels, registered protons with energies of Ep = 3–70 MeV and electrons with energies of Ee > 0.04 and >0.8 MeV, are analyzed. The data on electrons with Ee = 0.8–1.2 MeV, measured on the Express-A3 geostationary satellite, are also presented. Before the strong magnetic storm of December 14 (|Dst|max = 146 nT), the maximum of the outer belt electrons with the energy >0.7 MeV was observed at L ～ 4.5. After the storm, the fluxes of these electrons increased by more than an order of magnitude as compared to the prestorm level, and the maximum of a “new” belt shifted to L < 4 (minimal L reached by the GLONASS orbit). Under quiet geomagnetic conditions, solar protons with the energies >3 MeV fill only high-latitude legs of the GLONASS orbit. During the strong magnetic storm of December 15, the boundary of proton penetration into the magnetosphere almost merged with the orbital maximum of the proton radiation belt.  相似文献   

18.
Simulations of quiet time terrestrial H-ENA fluxes are shown. The simulations are obtained by using average proton differential fluxes from AMPTE-CCE/CHEM. A functional form which provides the ring current quiet time proton fluxes as a function of energy, L-shell and magnetic local time is also used. The energy neutral atom (ENA) fluxes are simulated at a specific location along the Geotail spacecraft orbit, where ENA data have been collected by the HEP-LD spectrometer. A detailed analysis of the ENA generation along the instrument look directions is presented, in order to evaluate the significance of the ENA signal with respect to the locations of ion sources and to the instrument energy resolution. At energies above 70 keV, we show that the ENA energy is directly related to the ion source location.  相似文献   

19.
The dynamics of wave disturbances in the ionospheric E region in the band of periods of thermal tidal waves and waves of planetary scales (T = 48, 72, and 192 h) has been studied based on the variations in the horizontal component of the geomagnetic field, observed at Paratunka and Barrow observatories in September–October 1999. It has been found that, at midlatitudes during high geomagnetic activity, the intensity of oscillations in the power spectra with T = 24 and 12 h varies with a periodicity of 16 days different from the periodicity of changes in the ΣKp index. The maximal deviations of these periods from the values under quiet conditions coincide with the maximal changes in the ΣKp index. The variations in the 48–192 h band of periods (especially with T ～192 h) intensify simultaneously with increasing geomagnetic activity. The intensity of this harmonic is several times as high as that of the harmonic with T ～ 24 h. The periodicity of changes in the harmonics intensity within the 48–192 h band coincides with the periodicity of changes in the ΣKp index. In the polar ionosphere, the effect of high geomagnetic activity is observed as an increase in the variations with a quasi-period of T ～ 24 h and as an appearance of variations in the 48–192 h band with the periodicity coinciding with the maximums in the ΣKp index variations.  相似文献   

20.
Disturbances in the solar wind density, geomagnetic field, and magnetospheric plasma density and fluxes are analyzed. The disturbances have the same sign and are close to each other in time. They accompany the process of amplitude modulation of Pc1 geomagnetic pulsations during the recovery phase of the moderate magnetic storm of April 10–11, 1997. The magnetospheric disturbances were recorded by ground-based observatories and on spacecraft in all local time sectors with insignificant time delays. It is concluded that in this case variations in the geomagnetic field and magnetospheric plasma density are primary, whereas the amplitude modulation of Pc1, 2 is a secondary manifestation of fast magnetosonic (FMS) waves that are generated during the interaction between the magnetosphere and solar wind density irregularities.  相似文献   

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