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971.
E.O. Falayi B.O. Adebesin O.S. Bolaji 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(3):985-1003
This work investigates the influence of coronal mass ejection (CME) on the time derivatives of horizontal geomagnetic and geoelectric fields, proxy parameters for identifying GICs. 16 events were identified for the year 2003 from the CORONAS-PHOTON spacecraft. Five of the events (May 29, June 9, October 28, October 29, and November 4) were extensively discussed over four magnetic observatories, were analyzed using the time derivatives of the horizontal geomagnetic (dH/dt) and geoelectric (EH) fields obtained from data of the INTERMAGNET network. It was observed that energy distributions of the wavelet power spectrum of the horizontal geoelectric field are noticed at the nighttime on both 29 May and 9 June 2003 across the stations. Daytime and nighttime intensification of energy distribution of the wavelet power spectrum of the horizontal geoelectric field are observed on both 28 and 29 October 2003 due to strong westward electrojet. The 4 November 2003 event depicts daytime amplification of energy distributions of the wavelet power spectrum across the stations. The highest correlation magnitude is obtained in the event of 4 November 2003 between dH/dt and EH relationships during the intense solar flare of class X 17.4. We observed that the correlation magnitude between dH/dt and EH increases with increase in CME activity. We concluded that the response of the surface impedance model for different stations plays a key role in determining the surface electric field strength, due to large electric field changes at different stations. 相似文献
972.
基于星上实时信号处理机的Chirp Scaling算法实现方法 总被引:3,自引:0,他引:3
基于改进的Chirp Scaling算法,提出了一种适用于星上实时信号处理机的高效成像处理实现方法,其核心思想也可应用于其它高分辨率星载SAR的精确成像算法.首先介绍了实时信号处理机的结构,分析了数据处理粒度及其并行流水处理结构.在此基础上,针对单个粒度的成像处理重新设计了算法流程,提出了一种高效的实现方法.利用实时信号处理机,对仿真的回波数据进行了成像处理实验,结果表明:在41?s内能够完成成像处理,成像处理速度和图像质量满足系统设计要求,从而验证了该方法的有效性. 相似文献
973.
Gordon Reikard 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Space weather forecasts are currently used in areas ranging from navigation and communication to electric power system operations. The relevant forecast horizons can range from as little as 24 h to several days. This paper analyzes the predictability of two major space weather measures using new time series methods, many of them derived from econometrics. The data sets are the Ap geomagnetic index and the solar radio flux at 10.7 cm. The methods tested include nonlinear regressions, neural networks, frequency domain algorithms, GARCH models (which utilize the residual variance), state transition models, and models that combine elements of several techniques. While combined models are complex, they can be programmed using modern statistical software. The data frequency is daily, and forecasting experiments are run over horizons ranging from 1 to 7 days. Two major conclusions stand out. First, the frequency domain method forecasts the Ap index more accurately than any time domain model, including both regressions and neural networks. This finding is very robust, and holds for all forecast horizons. Combining the frequency domain method with other techniques yields a further small improvement in accuracy. Second, the neural network forecasts the solar flux more accurately than any other method, although at short horizons (2 days or less) the regression and net yield similar results. The neural net does best when it includes measures of the long-term component in the data. 相似文献
974.
Il-Hyun Cho Young-Sil Kwak Katsuhide Marubashi Yeon-Han Kim Young-Deuk Park Heon-Young Chang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
We explore a possibility that the daily sea-level pressure (SLP) over South Korea responds to the high-speed solar wind event. This is of interest in two aspects: first, if there is a statistical association this can be another piece of evidence showing that various meteorological observables indeed respond to variations in the interplanetary environment. Second, this can be a very crucial observational constraint since most models proposed so far are expected to preferentially work in higher latitude regions than the low latitude region studied here. We have examined daily solar wind speed V, daily SLP difference ΔSLP, and daily log(BV2) using the superposed epoch analysis in which the key date is set such that the daily solar wind speed exceeds 800 km s−1. We find that the daily ΔSLP averaged out of 12 events reaches its peak at day +1 and gradually decreases back to its normal level. The amount of positive deviation of ΔSLP is +2.5 hPa. The duration of deviation is a few days. We also find that ΔSLP is well correlated with both the speed of solar wind and log(BV2). The obtained linear correlation coefficients and chance probabilities with one-day lag for two cases are r ? 0.81 with P > 99.9%, and r ? 0.84 with P > 99.9%, respectively. We conclude by briefly discussing future direction to pursue. 相似文献
975.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(6):1663-1672
Solar radio type IV bursts can sometimes show directivity, so that no burst is observed when the source region in located far from the solar disk center. This has recently been verified also from space observations, at decameter wavelengths, using a 3D-view to the Sun with STEREO and Wind satellites. It is unclear whether the directivity is caused by the emission mechanism, by reduced radio wave formation toward certain directions, or by absorption/blocking of radio waves along the line of sight. We present here observations of three type IV burst events that occurred on 23, 25, and 29 July 2004, and originated from the same active region. The source location of the first event was near the solar disk center and in the third event near the west limb. Our analysis shows that in the last two events the type IV bursts experienced partial cut-offs in their emission, that coincided with the appearance of shock-related type II bursts. The type II bursts were formed at the flanks and leading fronts of propagating coronal mass ejections (CMEs). These events support the suggestion of absorption toward directions where the type II shock regions are located. 相似文献
976.
为解决雷达图像仿真中海量地面材质数据的存储和加载问题,采用基于自适应最大行程长度编码和修正 偶对的压缩算法进行材质数据的压缩,从而有效地减少了数据的存储量,消除数据传输的瓶颈,提高了数据传输的 吞吐能力。压缩算法面向 GPU快速处理,得到压缩数据适用于 GPU进行快速解压。 相似文献
977.
978.
刘兴明 《海军航空工程学院学报》2011,26(6):691-694
为了减少反舰导弹受冲淡干扰的几率,要求末制导雷达在保证捕捉概率的同时尽量减小角度搜索范围。为此,提出了末制导雷达捕捉目标所需最小角度搜索范围模型,推导了最小角度搜索范围表达式及其对应的最佳开机距离表达式。在不同的探测距离下,以高亚声速反舰导弹为例进行了仿真计算。结果表明,最小角度搜索范围在+30°之内,小于某些反舰导弹... 相似文献
979.
980.