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Richa Trivedi Sudhir Jain Amit Jain A.K. Gwal 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The ionospheric Total Electron Content (TECs), derived by dual frequency signals from the Global Positioning System (GPS) recorded near the Indian equatorial anomaly region, Bhopal (23.2°N, 77.4°E, Geomagnetic 14.2°N) were analyzed for the period of January, 2005 to February, 2008. The work deals with monthly, diurnal, solar and magnetic activity variations on night-time enhancement in TEC. From a total of 157 night-time enhancements, 75 occur during pre-midnight and 82 post-midnight hours. The occurrence of night-time enhancement in TEC is utmost during summer months, followed by equinox and winter months. The occurrence of night-time enhancement in TEC decreases with increase in solar and magnetic activities. We observed that peak size and half amplitude duration are positively correlated, while time of occurrence of night-time enhancement in TEC and time of peak enhancement are negatively correlated with solar activity. The peak size, half amplitude duration, time of peak enhancement and time of occurrence of night-time enhancement in TEC shows negative correlation with magnetic activity. The results have been compared with the earlier ones and discussed in terms of possible source mechanism responsible for the enhancement at anomaly crest region. 相似文献
363.
Mariano Poisson Marcelo López Fuentes Cristina H. Mandrini Pascal Démoulin Etienne Pariat 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We study the extremely complex active region (AR) NOAA 10314, that was observed from March 13–19, 2003. This AR was the source of several energetic events, among them two major (X class) flares, along a few days. We follow the evolution of this AR since the very first stages of its emergence. From the photospheric evolution of the magnetic polarities observed with SOHO/MDI we infer the morphology of the flux tube that originates the AR. Using a computation technique that combines Local Correlation Tracking with magnetic induction constrains, we compute the rate of magnetic helicity injection at the photosphere during the observed evolution. From our results we conclude that the AR originated by the emergence of a severely deformed magnetic flux tube having a dominantly positive magnetic helicity. 相似文献
364.
Habibeh Valizadeh Alvan Farid Haydari Azad Shattri Mansor 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Pre-earthquake physical and chemical interactions in the earth’s ground may cause anomalies in latent heat flux, air and surface temperature. Earthquakes occur when the energy accumulated in rocks releases. Sometimes, the movements of the ground cause ruptures in the earth’s surface and sometimes the two sides of an existing fault shift towards each other. In a structurally complex and inhomogeneous collision region such as the Iranian Plateau, seismicity is not the result of activity of a single fault but is due to energy discharge in fault zones hundreds of kilometers wide. 相似文献
365.
Stefano Casadio Olivier Arino 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The South Atlantic Anomaly (SAA) has been monitored for 19 years using the Along Track Scanning Radiometer (ATSR) series of instruments onboard the ERS-1, ERS-2 and ENVISAT ESA satellites. The time evolution of the night-time particle induced noise in the short wavelength infrared (SWIR, 1.6 μm) and visible (VIS, 0.55 μm) channels of the ATSR instrument series have been analysed. The monthly location and extension of the SAA are inferred by fitting a two-dimensional, elliptical Gaussian function to the coordinates of the night-time hot spots detected over the SAA region. The location of the centre of the SAA is found to drift westwards with an average drift rate of about 0.24 deg/year and northward with an average drift rate of about 0.12 deg/year. Irregularities are found where the drift speed is inverted and the SAA moves eastward and southward. Results indicate that, as expected, the retrieved values of SAA’s strength and extension are anti-correlated with the solar activity expressed by the solar flux at 10.7 cm (F10.7). Finally, the peak-to-peak amplitude of the seasonal variation of the SAA strength, estimated from monthly VIS data, is found to be 30% of the average value with the annual to semiannual amplitude ratio of 1.38. 相似文献
366.
本文在绝对/对流不稳定性的理论框架下,对二维射流的稳定性进行了数值分析。研究表明射流流场各局部剖面是对流不稳定的,不会产生整体失稳,射流频率由流场中最大增长的不稳定频率确定。将一NACA012翼型放置于射流势流核心区中,改变翼型的偏转角度θ,可使射流剪切层频率与翼型尾流频率发生共振,整个流场产生自激振荡,加强了射流与外界流场和混合,并使射流发生矢量偏转。 相似文献
367.
以压缩拐角流动为例,对分离流中旋涡运动的热行为及其控制进行了数值模拟研究。研究结果表明,光滑表面上流动的分离特性及其热行为受到壁面温度的极大影响,提高壁面温度可以使分离点前移,再附点后移,分离范围扩大,涡心提高,而再附点附近及峰值热流则经历了一个先上升后下降的非单调变化过程;分离区和现附点附近的温度型与附着流差别明显,具有很高的峰值和很靠近物面的峰值点,从而造成高热流。而且温度梯度随壁温的不敏感性 相似文献
368.
线圈法漏磁探伤的信号特性分析 总被引:1,自引:0,他引:1
本文由标量磁位计算圆柱形点缺陷的漏磁场,然后计算穿过式线圈及旋转式线圈探测点缺陷的漏磁场产生的感应电动势,分析这些检测信号的特性并得出相应的结论。 相似文献
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