基于卫星数据和NRLMSISE-00模型的低轨道大气密度预报修正方法

NRLMSISE-00大气模型广泛应用于航天器定轨和预测等方面,但存在着较大的误差,尤其是在短期变化方面.为了提高低轨道大气密度短期预报的精度,我们提出了一种基于实测数据对NRLMSISE-00大气模型密度结果进行修正预报的方法:利用GRACE(Gravity Recovery and Climate Experiment)和CHAMP(Challenging Mini-Satellite Payload)卫星2002-2008年大气密度探测数据对NRLMSISE-00模型进行误差分析,获得模型的修正因子,再对模型的大气密度结果进行修正.采用该修正方法对GRACE-A和CHAMP卫星轨道上的大气密度进行3天短期预报试验验证,结果表明可显著提高大气密度的预报精度,在太阳活动低年,修正后的大气密度预报误差比NRLMSISE-00模型误差降低50%以上.     

Multiparticle statistical model of the solar wind

A multiparticle statistical approach to plasma (gas) modeling is presented, in which the fact that the macroscopic parameters are measured with finite resolution scales is taken into account [Minkova, 2004; 2005; 2007]. This approach is based on the Liouville theorem formulated for a stationary open system in the approximation of detailed dynamic balance with its surroundings. When the finite resolution scales of measuring instruments are taken into account, the plasma (gas) is described by multiparticle distribution functions. The latter are used to derive the probability distribution functions of fluctuations and the average values of macroscopic parameters. The multiparticle statistical approach allows a stationary solar wind model to be constructed under a number of simplifying assumptions. Its results for the average values of macroscopic parameters coincide with those of the two-particle kinetic model [Vasenin et al., 2003] and agree with inecliptic observational data.     

Computation and analysis of the geomagnetic field model in China and its adjacent area for 2003

Based on the geomagnetic data at 135 stations and 35 observatories in China in 2003, the Taylor polynomial model and the spherical cap harmonic model in China and its adjacent area for 2003 were established. In the model calculation, the truncation order of the model and the influences of the boundary restriction on the model calculation were carefully analyzed. The results show that the geomagnetic data used are precise and reliable, and the selection of the truncation order is reasonable. The Taylor polynomial model and the spherical cap harmonic model in China and its adjacent area established in this paper are consistent very well.     

2003年中国及邻区地磁场模型的计算与分析

根据2003年中国地区的135个测点和35个台站的地磁数据, 建立了2003年中国及邻区地磁场泰勒多项式模型和球冠谐模型. 在模型计算过程中, 细致地分析了模型的截断阶数和边界约束对模型计算的影响. 结果表明, 所使用的地磁观测资料是准确可靠的, 模型截断阶数的选取是合理的. 本文所建立的中国区域地磁场球冠谐模型与泰勒多项式模型具有良好的一致性.      

2003年11月份日全食期间“创新一号”卫星母线电压异常的诱因分析

对2003年11月份发生在南极附近地区的日食事件进行了扼要介绍；利用STK软件，对日食事件进行了仿真计算，分析了造成11月23日日全食发生期间，CX-1卫星的母线电压异常的诱因.基于CX-1的最新轨道数据，利用STK软件，仿真了2004年CX-1卫星面临的日食事件，并给出了详细的时间表.     

UVB solar radiation climatology for Mexico

The measurement of solar B band Ultraviolet radiation (UVB) should be considered a priority in Mexico due to implications on public health throughout the country (total population, 108 million), but this is not carried out at present. Installed sensors cover only 0.12% of the country. However, there are alternative methods for estimating UVB radiation to overcome the lack of surface data. The most successful of these are based on the use of satellites for environmental monitoring. In the present work, UVB maps are constructed for the entire country using a single, daily satellite measurement of UVB at solar noon from 1978-2003. Satellite-derived values are compared with the ground measurements by a surface station located in Mexico City in order to validate the former. Wavelet spectrum analysis is employed to this end. A close correlation is observed between the two sets of data. Moreover, there is qualitative correspondence between the spatial distribution of the satellite-derived data and the surface topography. The difference resulting throughout the period mentioned is <2% of the average annual cumulative energy.     

Time delays in the correlation between solar activity and the F2 region plasma frequency

The upper ionosphere electron density characterized by the critical frequency foF2 is correlated with solar activity when using monthly medians or averages from longer intervals. When shorter intervals are studied, time delays of different lengths in solar activity effects in the ionosphere are observed. The correlation between the foF2 values and the solar radiation intensity, given by the F10.7 index, is studied using the 1967–2003 data of mid-latitude ionosonde stations spaced at distances greater than 100° in geographical longitude. At which longitude the reaction of foF2 to the changes in solar activity appears sooner depends on the position of the interval studied in the 22-year solar cycle.     

Selection and ranking of ground motion models for seismic hazard analysis in the Pyrenees

The issue addressed in this paper is the objective selection of appropriate ground motion models for seismic hazard assessment in the Pyrenees. The method of Scherbaum et al. (2004a) is applied in order to rank eight published ground motion models relevant to intraplate or to low deformation rate contexts. This method is based on a transparent and data-driven process which quantifies the model fit and also measures how well the underlying model assumptions are met. The method is applied to 15 accelerometric records obtained in the Pyrenees for events of local magnitude between 4.8 and 5.1, corresponding to moment magnitudes ranging from 3.7 to 3.9. Only stations at rock sites are considered. A total of 720 spectral amplitudes are used to rank the selected ground motion models. Some control parameters of these models, such as magnitude and distance definitions, may vary from one model to the other. It is thus important to correct the selected models for their difference with respect to the magnitude and distance definitions used for the Pyrenean data. Our analysis shows that, with these corrections, some of the ground motion models successfully fit the data. These are the Lussou et al. (2001) and the Berge-Thierry et al. (2003) models. According to the selected ground motion models, a possible scenario of a magnitude 6 event is proposed; it predicts response spectra accelerations of 0.08–0.1 g at 1 Hz at a hypocentral distance of 10 km.     

Solar maximum epoch imprints in tree-ring width from Passo Fundo,Brazil (1741–2004)

A tree-ring thickness time series from Passo Fundo (Southern Brazil) for the interval 1741–2004 was studied by spectral, wavelet and cross-wavelet analyses in order to identify the non-stationary characteristics in tree-ring and sunspot number data. Periods corresponding to the solar cycles of 11, 22, and 80 yr were found. The 11 yr solar cycle is detected in tree-ring data only during maximum solar activity interval from 1764 to 1804, 1824 to 1884, and 1924 to 1984. The Hale 22 yr solar cycle was observed in tree-ring wavelet map for the 1764–1864 and 1904–2004 intervals. The Gleissberg solar cycle was also observed in tree-ring wavelet map for the 1844–1904 interval.     

Solar energetic events in the years 1996–2004. The analysis of their geoeffectiveness

Data concerning solar energetic events, published in 1996–2004 by the USAF/NOAA in the form of daily reports, have been collected. The analysis of the particular event types indicates that the degree of their geoeffectiveness depends on their size and on their solar disc location. The mere information that a solar X-flare (XRA) event or a Long Duration XRA Event (LDE) has occurred on the solar disc is insufficient to produce a relevant forecast of geomagnetic disturbances. The probability increases if the XRA is of class X which has occurred on the solar disk in central region (30 °E, 30 °W; 30 °S, 30 °N). XRAs associated with metric type II and IV radio bursts (RSP II and RSP IV), which occurred on the solar disc in this region will very probably cause a geomagnetic disturbance not only if X class are involved, but also M class and B–C class. The Disappearance of Solar Filament (DSF) data cannot be used in forecasting geomagnetic disturbances. The geoeffective and nongeoeffective DSFs are too disproportional. jboch@ig.cas.cz fridrich@geomag.sk     

行星际背景太阳风的三维MHD数值模拟

近地空间的太阳风参数预报具有重要的科学研究意义和实际应用价值,三维磁流体力学（MHD）数值模拟是太阳风参数预报的重要手段.本文建立了一套基于经验模型的三维MHD数值模型.模型的内边界设置在0.1天文单位（AU）处,在六片网格系统下利用TVD Lax-Friedrich格式求解理想MHD方程组,采用扩散法消除磁场的散度.模型以GONG的观测磁图作为输入数据,利用经验模型并结合卫星观测特征确定内边界条件.边界条件中保留了6个可调参数,以便适当调整参数使其方便适合模拟不同太阳活动期的太阳风.利用该模型分别模拟了2007年和2016年的背景太阳风,得到了太阳风速度、密度、温度和磁场强度,这些参数与ACE/WIND卫星观测符合较好.     

Peak characteristics of F2 region over Tucumán: Predictions and measurements

Ionosonde measurements obtained at Tucumán are used to check the validity of the International Reference Ionosphere model to predict the maximum electron density of the F2 region (NmF2) and its height (hmF2) over this station. Data corresponding to different months and solar activity conditions are considered. CCIR and URSI options are used to model calculations. The results show that, generally, the predictions of hmF2 are better than those of NmF2. Disagreements between predicted and measured NmF2 values are observed and the consequences in the vertical total electron content modeling are stressed.     

Monitoring of solar proton events at altitudes up to 1000 km: Data from the Russian space experiments. Solar proton effects in the Earth’s ozonosphere

The paper illustrates the opportunities provided by the use of data from Russian satellite experiments (CORONAS and Universitetsky-Tatiana of Meteor series) on the measurement of fluxes and spectra of solar cosmic rays at altitudes of 370–1000 km for simulation of the ozonosphere state. The results of photochemical simulation and observational data analysis showing the influence of solar protons on polar ozonosphere and lower ionosphere in periods of solar proton events (SPE) on November 4, 2001, October 28, 2003, and January 16, 2005 are presented. It is shown that the solar proton action causes ozone depletion in the mesosphere above the polar regions. The strongest depletion (up to 70%) was caused by the SPE that occurred on October 28, 2003.     

Petrology of lavas from the 2004–2005 flank eruption of Mt. Etna,Italy: inferences on the dynamics of magma in the shallow plumbing system

Following the 2001 and 2002–2003 flank eruptions, activity resumed at Mt. Etna on 7 September 2004 and lasted for about 6 months. This paper presents new petrographic, major and trace element, and Sr–Nd isotope data from sequential samples collected during the entire 2004–2005 eruption. The progressive change of lava composition allowed defining three phases that correspond to different processes controlling magma dynamics inside the central volcano conduits. The compositional variability of products erupted up to 24 September is well reproduced by a fractional crystallization model that involves magma already stored at shallow depth since the 2002–2003 eruption. The progressive mixing of this magma with a distinct new one rising within the central conduits is clearly revealed by the composition of the products erupted from 24 September to 15 October. After 15 October, the contribution from the new magma gradually becomes predominant, and the efficiency of the mixing process ensures the emission of homogeneous products up to the end of the eruption. Our results give insights into the complex conditions of magma storage and evolution in the shallow plumbing system of Mt. Etna during a flank eruption. Furthermore, they confirm that the 2004–2005 activity at Etna was triggered by regional movements of the eastern flank of the volcano. They caused the opening of a complex fracture zone extending ESE which drained a magma stored at shallow depth since the 2002–2003 eruption. This process favored the ascent of a different magma in the central conduits, which began to be erupted on 24 September without any significant change in eruptive style, deformation, and seismicity until the end of eruption.     

Changes in the chemical composition of the atmosphere in the polar regions of the Earth after solar proton flares (3d modeling)

The paper presents the results of numerical photochemical simulations of the impact of the most powerful solar proton flares during the 23rd solar cycle on the ozonosphere in the polar regions of the Earth. A global 3D photochemical model, CHARM, developed at Central Aerological Observatory (CAO) was used in the simulations. The model introduces an additional source of nitrogen atoms and OH radicals. These components are formed due to the ionization effect of solar protons in the Earth’s atmosphere. The ionization rate was determined from data on proton fluxes measured by GOES satellites. The production rate of additional NO _x and HО _x molecules per ion pair was based on published theoretical studies. It is shown that the most intense flares in the 23rd solar cycle (2000, 2001, and 2003) destroyed ozone in the mesosphere to a great extent (sometimes completely, for example, during the July 14, 2000, event). It is found that the response of ozone to solar proton events follows a seasonal pattern. For the first time, the long-term effect of solar proton events is identified; it is approximately one year.     

Regional response of the mesosphere–lower thermosphere dynamics over Scandinavia to solar proton events and geomagnetic storms in late October 2003

The short-term regional responses of the mesosphere–lower thermosphere (MLT) dynamics over Scandinavia to the exceptionally strong solar storms with their accompanying solar proton fluxes on the Earth in late October 2003 have been investigated using radar measurements at Andenes (69°N, 16°E) and Esrange (68°N, 21°E). Several solar activity storms resulted in solar proton events (SPEs) at this time, but a particularly active period of high proton fluxes occurred between 28 and 31 October 2003. The significant temperature drop (∼25 K), detected by the meteor radar at Andenes at altitude ∼90 km, was in line with the enhancement of the proton fluxes and was caused by the dramatic reduction of the ozone in the high-latitude middle atmosphere monitored by satellite measurements. This exceptionally strong phenomenon in late October 2003 was composed of three geomagnetic storms, with the first one occurring in the daytime of 29 October and the other two storms in the nighttime of 29 and 30 October, respectively. The responses of the prevailing wind and the main tides (24- and 12-h tides) were studied in detail. It was found that the response of the MLT dynamics to the first geomagnetic storm occurring in the daytime and accompanied by solar proton fluxes is very different from those to the second and third geomagnetic storms with onsets during the nighttime. Some physical mechanisms have been suggested in order to explain the observed short-term variability of the MLT dynamics. This case study revealed the impact of the SPEs observed in late October 2003 and the timing of the geomagnetic storms on the MLT neutral wind responses observed over Scandinavia.     

Kalman filter-based algorithms for monitoring the ionosphere and plasmasphere with GPS in near-real time

Data collected from a GPS receiver located at low latitudes in the American sector are used to investigate the performance of the WinTEC algorithm [Anghel et al., 2008a, Kalman filter-based algorithm for near realtime monitoring of the ionosphere using dual frequency GPS data. GPS Solutions, accepted for publication; for different ionospheric modeling techniques: the single-shell linear, quadratic, and cubic approaches, and the multi-shell linear approach. Our results indicate that the quadratic and cubic approaches perform much better than the single-shell and multi-shell linear approaches in terms of post-fit residuals. The performance of the algorithm for the cubic approach is then further tested by comparing the vertical TEC predicted by WinTEC and USTEC [Spencer et al., 2004. Ionospheric data assimilation methods for geodetic applications. In: Proceedings of IEEE PLANS, Monterey, CA, 26–29 April, pp. 510–517] at five North American stations. In addition, since the GPS-derived total electron content (TEC) contains contributions from both ionospheric and plasmaspheric sections of the GPS ray paths, in an effort to improve the accuracy of the TEC retrievals, a new data assimilation module that uses background information from an empirical plasmaspheric model [Gallagher et al., 1988. An empirical model of the Earth's plasmasphere. Advances in Space Research 8, (8)15–(8)24] has been incorporated into the WinTEC algorithm. The new Kalman filter-based algorithm estimates both the ionospheric and plasmaspheric electron contents, the combined satellite and receiver biases, and the estimation error covariance matrix, in a single-site or network solution. To evaluate the effect of the plasmaspheric component on the estimated biases and total TEC and to assess the performance of the newly developed algorithm, we compare the WinTEC results, with and without the plasmaspheric term included, at three GPS receivers located at different latitudes in the American sector, during a solar minimum period characterized by quiet and moderate geomagnetic conditions. We also investigate the consistency of our plasmaspheric results by taking advantage of the specific donut-shaped geometry of the plasmasphere and applying the technique at 12 stations distributed roughly over four geomagnetic latitudes and three longitude sectors.