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The hourly averaged Polar Cap (PC) index was used as the input parameter for the ring current index Dst variation forecasting. The PC index is known to describe well the principal features of the interplanetary magnetic field as well as the total energy input to the magnetosphere. This allowed us to design a neural network that was able to forecast the Dst variations 1 h ahead. 1995 PC and Dst data sets were used for training and testing and 1997 data sets were used for validation. From 15 moderate and strong geomagnetic storms observed during 1997, 10 were successfully forecasted. In 3 cases the observed minimum Dst value was less than the predicted value, and only in 3 cases the neural network was not able to reproduce the features of the geomagnetic storm. 相似文献
3.
Based on ion distribution function found from the dynamic equation, the density distribution of He+ ions originating from the polar ionosphere and up-flowing along the magnetic field line is studied during quiet and weakly disturbed geomagnetic conditions. The results show the following. (1) The ionospheric up-flowing He+ ions mainly reside in the inner magnetosphere and their density has a negative radial gradient. (2) The ionospheric up-flowing He+ ion distributions along the magnetic field line are mainly controlled by gravity and the geomagnetic field configuration. Larger the gravity, larger is the ion density. Smaller the intensity of magnetic field, smaller is the ion density. (3) If the geomagnetic activity index Kp is high, more up-flowing He+ ions will enter the magnetosphere and the region where the up-flowing ions are dominant will grow. This is consistent with observations of ionospheric up-flowing ions. Some features of the geopause can be understood based on our theoretical results. 相似文献
4.
785 traces of vertical components from shallow earthquakes recorded by 10 CDSN (Chinese Digital Seismographic Network) stations
and 5 GSN (Global Seismographic Network) stations were collected to study the attenuation characteristics ofL
g coda in the Chinese continent and its adjacent regions. The records were processed first using the stack spectral ratio method
to obtain the average values ofQ
0 (Q at 1Hz) and η, the frequency dependence, ofL
g coda in the ellipses corresponding to the paths. The back-projection technique was then employed to obtain the tomographic
maps ofQ
0 and η values, and the distribution of their errors. Results indicate that in the studied areaQ
0 varies between 200 and 500. The lowest value ofQ
0 exists in the Yun-nan-Tibetan region, while the highest value ofQ
0 occurs in the southern edge of Siberian platform. η varies between 0.3 and 0.8. For most part of the studied area η varies
inversely withQ
0. 相似文献
5.
Based on satellite observation data, using dynamics equation, the ionospheric O+ ion’s distribution in the synchronous altitude region for different geomagnetic activity indexK
p is studied by theoretical modeling and numerical analyzing, and semi-empirical models for the O+ ion’s density and flux versus longitude in the synchronous altitude region for differentK
p
are given. The main results show that in the synchronous altitude region: (i) The O+ ion’s density and flux in day-side are larger than those in nightside. (ii) With longitude changing, the higher the geomagnetic
activity indexK
p
is, the higher the O+ ion’s density and flux, and their variation amplitude will be. The O+ ion’s density and flux whenK
p ≥ 6 will be about ten times as great as that whenK
p
= 0. (iii) WhenK
p
= 0 orK
p ≥ 6, the O+ ion’s density reaches maximum at longitudes 120° and 240° respectively, and minimum in the magnetotail. WhenK
p
= 3−5, the O+ ion’s density gets to maximum at longitude 0°, and minimum in the magnetotail. However, the O+ ion’s flux reaches maximum at longitude 120° and 240° respectively, and minimum in the magnetotail for anyK
p
value. 相似文献
6.
Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang MS6.1 earthquake and the Ludian MS6.5 earthquake in 2014. We processed the geomagnetic vertical component diurnal variation data by the spatial correlation method. The results show that during the period from April 1 to May 20, 2014,there existed quasi-synchronous decrease changes in the coefficient curves between the five geomagnetic stations of Guiyang,Hechi,Nanshan,Muli,Yongning and Xinyi and Hongshan stations.Furthermore,there was a high gradient zone in the normalized correlation coefficient contour map with background values removed. The epicenters of the Yingjiang MS6.1 earthquake and the Ludian MS6.5 earthquake are located in the gradient zone or near the gradient zone. 相似文献
7.
The monthly means of north component X of geomagnetic field from 16 observatories during 1984–1988 were analyzed using the
Sompi spectral analysis technique Most of these observatories are located in China. The analysis of the semiannual variations
indicates that the latitude has no apparent effect on the X component. This clearly implies that the source field mode of
semiannual variations cannot simply be described by using the p
1
0
mode. Using the p
1
0
mode to estimate the inductive scale lengthC in the semiannual period, the value ofC at each observatory would be biased significantly. The purpose of this study is to find which kind of modes is optimal for
estimating the values ofC corresponding to the semiannual variations. The results show that a composite mode, involving five terms P
n
0
(n = 1,, 5), might be a reasonable and acceptable one 相似文献
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9.
分析距离九寨沟MS7.0地震震中分别为65 km、254 km和238 km的松潘地磁台、成都地磁台和天水地磁台2017年连续观测结果,发现九寨沟地震前,松潘地磁台出现异常变化,主要表现为2017年5月开始,松潘地磁台长时间垂直分量累积变化量达40 nT。短时间内也存在地磁场突变,最高可达10 nT,而成都地磁台和天水地磁台地磁场无明显异常。通过对观测数据的详细检查发现松潘地磁台很多观测日的最后一个观测值与后一观测日的第一个观测值相差超过1 nT,因此认为九寨沟地震前观测数据的异常是由观测系统异常导致。对三个台站地磁场垂直分量日变化的统计分析发现垂直分量在不同时段相关性保持一致,说明地震前短时间内不存在地磁垂直分量的明显异常变化,三个台站地磁场日变化的差异是由地下介质性质不同导致。岩石圈磁场在震中西侧区域出现正负异常交替现象,这可能与九寨沟地震的孕育有关。 相似文献
10.
The results from Raman spectroscopy analysis of salt aqueous solutions at −170°C demonstrate that for those clearly sharp
iron peaks whose Raman wavenumber is close to each other such as NO
3
−
and CO
3
2−
, their original shape could be restorable by the stripping technique, and that ice’s sharp characteristic peak 3090–3109
cm−1) is steady, while the spectrum band of the complex compound (nCl−-[H+-OH−]n) chlorine ion combined chemically with water molecule is 3401–3413 cm−1. On the other hand, the research shows that the higher the negative iron concentration, the stronger its Raman characteristic
peak intensity and the smaller the ice’s. Based on the number of data and theoretical work, the strong correlation of the
molar concentration of negative ion with the S
i/S
H
2O band area ratio is built up. Moreover, the developed Raman method is successfully used in the component analysis of the
field fluid inclusions from Silurian sandstone in Tarim basin. 相似文献
11.
We have collected 432 vertical component records from 45 stations of new CENC （China Earthquake Network Center） in Chinese mainland and adjacent regions. These records were used to calculate Q0 （Q at 1Hz） and η values of Lg coda from each station by the stack spectral ratio （SSR） method. Then the tomography method was applied to obtaining lateral variation of Q0 and η values in Chinese mainland and adjacent regions. The result indicates that Q0 value varies between 150 and 600 in the studied areas. Yunnan, southwest Sichuan, and northwest Myanmar show the lowest Q0 value （Q0〈240） and the crust of these regions is characterized by complicated crack and strong hydrothermal activity. The highest Q0 value （Qo〉510） exists in the border of southern Mongolia, Alxa and Ordos block. The η value varies between 0.45 and 0.75 in Chinese mainland and its adjacent regions. 相似文献
12.
The discussion in the preceding paper is restricted to the uncertainties in magnetic-field-iine tracing in the magnetosphere resulting from published standard errors in the spherical harmonic coefficients that define the axisymmetric part of the internal geomagnetic field (i.e. gn0 ± gn0). Numerical estimates of these uncertainties based on an analytic equation for axisymmetric field lines are in excellent agreement with independent computational estimates based on stepwise numerical integration along magnetic field lines. This comparison confirms the accuracy of the computer program used in the present paper to estimate the uncertainties in magnetic-field-line tracing that arise from published standard errors in the full set of spherical harmonic coefficients, which define the complete (non-axisymmetric) internal geomagnetic field (i.e. gnm ± gnm and hnm ± hnm). An algorithm is formulated that greatly reduces the computing time required to estimate these uncertainties in magnetic-field-line tracing. The validity of this algorithm is checked numerically for both the axisymmetric part of the internal geomagnetic field in the general case (1 n 10) and the complete internal geomagnetic field in a restrictive case (0 m n, 1 n 3). On this basis it is assumed that the algorithm can be used with confidence in those cases for which the computing time would otherwise be prohibitively long. For the complete internal geomagnetic field, the maximum characteristic uncertainty in the geocentric distance of a field line that crosses the geomagnetic equator at a nominal dipolar distance of 2 RE is typically 100 km. The corresponding characteristic uncertainty for a field line that crosses the geomagnetic equator at a nominal dipolar distance of 6 RE is typically 500 km. Histograms and scatter plots showing the characteristic uncertainties associated with magnetic-field-line tracing in the magnetosphere are presented for a range of illustrative examples. Finally, estimates are given for the maximum uncertainties in the locations of the conjugate points of selected geophysical observatories. Numerical estimates of the uncertainties in magnetic-field-line tracing in the magnetosphere, including the associated uncertainties in thelocations of the conjugate points of geophysical observatories, should be regarded as first approximations in the sense that these estimates are only as accurate as the published standard errors in the full set of spherical harmomic coefficients. As in the preceding paper, howerver, all computational techniques developed in this paper can be used to derive more realistic estimates of the uncertainties in magnetic-field-line tracing in the magnetosphere, following further progress in the determination of more accurate standard errors in the spherical harmonic coefficients.Also Visiting Reader in Physics, University of Sussex, Palmer, Brighton, BN1 9QH, UK 相似文献
13.
Yogui GT Santos MC Bertozzi CP Sericano JL Montone RC 《Marine pollution bulletin》2011,62(12):2666-2670
Limited information is available in the literature on the levels of brominated flame retardants in the southern hemisphere. This study presents concentrations of polybrominated diphenyl ethers (PBDEs) in the blubber of small cetaceans from the coast of São Paulo (Brazil), southwestern Atlantic. PBDE levels were highest in Stenellafrontalis (770 ng g−1 lipid) followed by Stenobredanensis (475 ng g−1 lipid), Sotaliaguianensis (65.6 ng g−1 lipid), Tursiopstruncatus (64.2 ng g−1 lipid) and Pontoporiablainvillei (60.3 ng g−1 lipid). In general, continental shelf individuals exhibited higher contamination than inshore animals. This might be related to larger prey items consumed by continental shelf dolphins. The pattern of contamination indicates that Penta-BDE commercial mixtures are a major source of PBDEs to top predators in the southwestern Atlantic. Congeners found in Octa-BDE formulations were not detected in the investigated animals. 相似文献
14.
针对高邮-宝应4.9级地震发生前后附近地区未发生其它中等以上地震、地震事件孤立及周边地磁台站分布较密有利于研究地震地磁异常时空特征的特点,较为系统地分析总结了该地震发生前后地磁谐波振幅比的变化特征,研究结果进一步验证了目前对地磁谐波振幅比异常特征的认识,即地磁谐波振幅比异常特征表现出与地电阻率类似的下降-转折-恢复上升的异常变化过程,地震一般发生在异常转折或恢复上升过程中,距震中较近的台站会出现不同步现象——南北向与东西向的不同步以及长短周期的不同步。 相似文献
15.
Francesco Ricciardi Valerio Matozzo Maria Gabriella Marin 《Marine pollution bulletin》2008,57(6-12):365
Since it is often difficult to estimate possible adverse effects due to contamination in selected ecosystems, multi-species biomonitoring may provide more information, taking into account different routes of exposure, ecological roles and metabolic capabilities of animals. In this context, we exposed for 7 days the mussel Mytilus galloprovincialis and the crab Carcinus aestuarii to 4-nonylphenol (NP), a well-known xenoestrogen. In mussels (0–0.2 mg NP l−1), we measured NP bioaccumulation in soft tissues and vitellogenin (Vg)-like protein levels in digestive glands from both males and females by the alkali-labile phosphate assay (ALP). As no reference data were available for crab exposure, the NP 96-h LC50 value was previously determined. Then, in sublethally exposed (0–1.0 mg NP l−1) male crabs, NP bioaccumulation and Vg levels were measured in hemolymph, gonads and digestive gland. Bioaccumulation of NP increased from 43 to 371 μg g−1 d.w. in mussels, and from 3.6 to 37 μg g−1 d.w. in crabs, depending on the NP concentration in water. Dose-dependent Vg-like protein induction was observed in both species, appearing to be related to NP bioaccumulation, although a partial decrease was recorded at the highest concentration tested. A similar trend was observed in both digestive gland and gonad of exposed crabs; Vg increased to a lesser extent, although significantly, in hemolymph. Results demonstrated that NP induces Vg synthesis both in male and female mussels, as well as in male crabs. On the basis of the responsiveness of both species investigated, a multi-species approach is indicated in biomonitoring programmes. 相似文献
16.
2017年精河MS6.6地震前地磁异常特征分析 总被引：1，自引：0，他引：1
2017年8月9精河发生MS6.6地震,距震中300km范围内的温泉台、克拉玛依台、乌鲁木齐台捕捉到此次地震前的地磁异常信息,本文对此进行了分析和总结,结论如下：①地磁谐波振幅比反应了观测点深部电阻率变化,2016年呼图壁MS6.2、此次精河MS6.6地震均发生在克拉玛依台地磁谐波振幅比异常下降之后的转折和恢复阶段;②震前83天、21天沿北天山断裂带分布的地磁台站逐日比和加卸载响应比均成组出现超限的高值,且异常高值的空间分布与震中位置有一定关联;③全国大陆地磁台站震前34天出现低点位移突变分界线,且异常集中于震中附近。 相似文献
17.
The relation between the gravity variation features and Ms=8.1 earthquake in Qinghai-Xizang monitoring area is analyzed preliminarily,by using spatial dynamic variation results of regional gravity field from absolute gravity and relative gravity observation in 1998 and 2000.The results show that:1)Ms\8.1 earthquake in Kulun mountain pass westem occurred in the gravity variation high gradient near gravity‘s high negative variation;2)The Main tectonic deformation and emnergy accumulation before MS=8.1 earthquake are distributed at south side of the epicenter;3)The range of gravity‘s high negative variation at east of the MS=8.1 earthquake epicenter relatively coincides with that rupture region according to field geology investigation;4)Gravity variation distribution in high negative value region is just consistent with the second shear strain‘s high value region of strain field obtained from GPS observation. 相似文献
18.
Wen-Yao Xu 《Pure and Applied Geophysics》1989,131(3):371-393
Geomagnetically quiet day variations in the polar region are reviewed with respect to geomagnetic field variation, ionospheric plasma convection, electric field and current. Persistently existing field-aligned currents are the main source of the polar regionSq. Consequently, the morphology and variability of the polar regionSq largely depend upon both field-aligned currents and ionospheric conductivity. Since field-aligned currents are the major linkage between the ionosphere and the magnetosphere, the latter is controlled by solar wind state, in particular, the interplanetary magnetic field, the polar regionSq exhibits remarkable IMF dependence. 相似文献
19.