极地科学数据关联方法及应用研究

为了从海量极地科学数据中准确、智能地发现用户所需要的数据,首先,系统研究分析极地科学数据特征,挖掘极地科学数据本身隐含的语义信息,建立极地科学数据关联指标体系;其次,研究极地科学数据关联方法,最后设计并实现极地科学数据关联查询应用原型系统。以极地科学数据共享平台的元数据作为语料库,自动抽取极地科学数据关联指标数据,实现极地科学数据集之间的自动关联。应用实践表明,利用极地科学数据关联方法不仅可直接检索出满足条件的数据,还可以检索出潜在的相关联的数据。该关联方法研究可促进极地科学数据的集成、融合与共享应用。     

对流电场产生电离层扰动的典型事例

用欧空局ＥＩＳＣＡＴ极光区非相干散射雷达观测资料、南极中山站电离层垂测站和我国１２０°Ｅ电离层站链ｆ０Ｆ２资料，分析了１９９１年５月２～３日一次主要由磁层对流引起的电离层扰动过程。从形态特征上看，它与热层中性大气参与的动力耦合过程明显地不同。对照比较表明，这是一次典型的磁层－电离层电动耦合事例。全球地磁站网资料从另一侧面证实，本文讨论的耦合机制是正确的。     

Multixenobiotic resistance, acetyl-choline esterase activity and total oxyradical scavenging capacity of the Arctic spider crab, Hyasaraneus, following exposure to bisphenol A, tetra bromo diphenyl ether and diallyl phthalate

The Arctic has become a sink for persistent organic pollutants (POPs) originating from lower latitudes, and relatively high levels have been found in different biota. Recent studies have identified detrimental effects on wildlife including endocrine disruption, impairment of enzyme activity, and reduced immune function. The Arctic spider crab, Hyas araneus, shown interesting potential for its use as sentinel organism in polar ecosystems. This study investigated the effect of 2,2',4,4'-tetra bromo diphenyl ether (BPDE), bisphenol A (BPA), and diallyl phthalte (DPA) on H. araneus in a three weeks exposure study. Expression of multixenibiotic resistance (MXR) proteins has been studied using the C219 monoclonal antibody which allows identifying an immunoreactive protein of 40 kDa in the digestive gland while no such protein could be observed in the gills. Expression of this protein was increased by exposure to DPA (+75%; p<0.05, n=10). All compounds significantly affected muscle acetylcholine esterase (AChE) activity (p<0.05, n=10) with 50 microg/L DPA having the strongest effect by lowering the value to 37% of control. The total oxyradical scavenging capacity measured in the digestive gland toward peroxyl, hydroxyl and peroxynitrite was also significantly reduced indicating a decreased resistance to oxidative stress generated by DPA (p<0.05, n=5). These results thus suggest the potential detrimental effects of DPA even at concentration as low as 50 microg/L on H. araneus.     

Global plasmaspheric TEC and its relative contribution to GPS TEC

The plasmaspheric electron content is directly estimated from the global positioning system (GPS) data onboard JASON-1 Satellite for the first time. Similarly, the ground-based GPS total electron content (TEC) is estimated using about 1000 GPS receivers distributed around the globe. The relative contribution of the plasmaspheric electron content to the ground-based GPS TEC is then estimated globally using these two independent simultaneous measurements; namely ground-based GPS TEC and JASON-1 GPS TEC. Results presented here include data from 3 months of different solar cycle conditions (October 2003, May 2005, and December 2006). The global comparison between the two independent measurements was performed by dividing the data into three different regions; equatorial, mid- and high-latitude regions. This division is essential as the GPS raypaths traverse different distances through the plasmasphere at different latitudes. The raypath length through the plasmasphere decreases as latitude increases. The relative contribution of the plasmaspheric electron content exhibits a diurnal variation that depends on latitude with minimum contribution (10%) during daytime and maximum (up to 60%) at night. The contribution is also maximum at the equatorial region where the GPS raypath traverses a long distance through the plasmasphere compared to its length in mid- and high-latitude regions. Finally, the solar cycle variation of plasmaspheric contribution is also reported globally.     

The Polar Cap (PC) indices: Relations to solar wind parameters and global magnetic activity

The polar geomagnetic activity resulting from solar wind–magnetosphere interactions can be characterized the Polar Cap (PC) indices, PCN and PCS. PC index values are derived from polar magnetic variations calibrated on a statistical basis such that the index approximate values in units of mV/m of the interplanetary “geo-effective” (or “merging”) electric field (E_M) conveyed by the solar wind. The timing and amplitude relations of the PC index to solar wind plasma and magnetic field parameters are reported. The solar wind effects are parameterized in terms of the geo-effective electric field (E_M) and the dynamical pressure (P_DYN). The PC index has a delayed and damped response to E_M variations and display saturation-like effects for E_M values exceeding 10 mV/m. Steady or slowly varying levels of solar wind dynamical pressure have little or no impact on the PC index above the effects related to E_M for which the solar wind velocity is also a factor. Sharp increases in the dynamical pressure generate impulsive variations in the PC index comprising a initial negative impulse of 5–10 min duration followed by a positive impulse lasting 10–20 min. Typical amplitudes of both the negative and the positive impulses are 0.2–0.5 units. A sharp decrease in the pressure produces the inverse sequence of pulses in the PC index. Auroral substorm activity represented by the AL index level has a marked influence on the average PC/E_M level at the transition from very quiet (AL0 nT) to disturbed conditions while more or less disturbed conditions (AL<−100 nT) have no systematic effect on the average PC/E_M values. At distinct substorm events the PC/E_M ratio has a minimum (0.8) in the pre-onset phase at around 20 min before substorm onset. The average ratio gradually increases in the expansion phase to reach a maximum value (1.1) at around 40 min after substorm onset (or 20 min after the largest (negative) peak in AL). At substorm recovery during the next 2 h the PC/E_M ratio decreases. Finally, we report on the application of polar magnetic variations to model the disturbance storm time (Dst) index development during magnetic storms by using the PC index as a source function to quantify the energy input to the ring current representing accumulated storm energy and characterized by the Dst index.     

Ionospheric electromagnetic perturbations observed on DEMETER satellite before Chile M7.9 earthquake

Based on the ionospheric electromagnetic data observed on DEMETER satellite of France, the ionospheric electromagnetic signals were analyzed within 10 days before Chile M7.9 earthquake on November 14, 2007. It is found that, low frequency electromagnetic disturbances began to increase in a large scale of latitude, and reached to a maximum one week prior to the earthquake, and at about three days before the quake, the peak values shifted to lower latitude. Taking three days as a group, spatial images of a fe...     

Possible ion-acoustic soliton formation in the ionospheric perturbations observed on DEMETER before the 2007 Pu’er earthquake

The data of ionospheric perturbations observed on DEMETER before the 2007 Pu’er earthquake are analyzed. The three-component plasma (ions, electrons and heavy ions) is studied in the fluid concept. The linear dispersion relation for ion-acoustic wave is found in the presence of heavy ions. The nonlinear dynamics is studied for arbitrary amplitude of the wave. The Sagdeev potential is calculated, which shows that solitary structure exists for Mach number within a range defined by the presence of heavy ions. ...     

A climatological study of nocturnal equatorial F-region irregularities at the west Pacific longitudes by using phase fluctuations of the global positioning system

This study investigated a long-term climatology of nocturnal equatorial F-region irregularities by using phase fluctuations of the global positioning system during the solar cycle of 1996–2006 at the west Pacific longitudes. The results showed that the distribution of the occurrence of irregularities is a two-peak pattern, which peaks in equinoxes with a shallow/deep dip in June/December solstice during high solar activity but with two about the same dips in magnitude in both June and December solstices during low solar activity. Moreover, the most interesting longitudinal effect in the area is in solstice occurrences of irregularities during high solar activity that the irregularities in December solstice months develop easier in the west area but those in June solstice months develop easier in the east area.     

On the spectrum of mid-latitude sporadic-E irregularities

We discuss the creation of mid-latitude sporadic-E plasma irregularities (with length-scales smaller than sporadic layer thickness) by the neutral atmosphere turbulence. Using fluid equations, the relation between plasma density fluctuations and the velocity field of neutrals is derived. After a brief discussion of the relevant neutral turbulence, the analytical expression for the power spectrum of plasma irregularities is obtained. This expression allows a power-law type of experimental irregularity spectra (the spectral index depends on sporadic-E characteristics) and possible departures in detail of the irregularity spectra from the power-law form to be explained. In addition, it allows us to make estimates of length-scales at which such departures must occur.