本文關(guān)鍵詞： 頻高圖 圖像處理 反演 夜間增強(qiáng)　出處：《武漢大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：電離層探測(cè)得到的主要結(jié)果是以頻高圖的方式顯示,獲取頻高圖中的特征參數(shù)和電子密度剖面一直以來都是電離層研究工作者的重要目標(biāo)。從這些參數(shù)信息和電子密度剖面可以大概了解電離層的結(jié)構(gòu)和狀態(tài)變化,進(jìn)而更加深入地對(duì)電離層進(jìn)行分析和研究。為了準(zhǔn)確獲取日本區(qū)域電離層頻高圖中的特征參數(shù)和電子密度剖面,本文提出了一種利用數(shù)字圖像處理等技術(shù)對(duì)頻高圖進(jìn)行轉(zhuǎn)換的方法,然后運(yùn)用此方法對(duì)當(dāng)?shù)仉婋x層夜間的異�，F(xiàn)象進(jìn)行分析,并給出觸發(fā)機(jī)制的物理解釋。主要內(nèi)容包括:1.提出了電離層頻高圖轉(zhuǎn)換的一種新方法。利用圖像處理中的Radon變換和最大類間方差法對(duì)頻高圖濾噪優(yōu)化,并運(yùn)用連通分量標(biāo)記法對(duì)濾噪后出現(xiàn)的斷裂和弱化現(xiàn)象進(jìn)行增強(qiáng);然后對(duì)頻高圖中的回波描跡幅度信息格式化,寫入到可以被SAO Explorer軟件識(shí)別的SBF格式文件中;最后運(yùn)用軟件自帶的ARTIST算法對(duì)轉(zhuǎn)換后的頻高圖進(jìn)行自動(dòng)度量和電子密度剖面的反演。將此方法中的圖像處理和格式轉(zhuǎn)換過程編寫為電離層頻高圖處理軟件。運(yùn)用此軟件對(duì)Okinawa電離層探測(cè)站點(diǎn)的頻高圖數(shù)據(jù)進(jìn)行實(shí)例統(tǒng)計(jì)分析,對(duì)頻高圖轉(zhuǎn)換前后度量得到的電離層F2層臨界頻率f0F2統(tǒng)計(jì)對(duì)比分析。結(jié)果表明該方法具有較高的準(zhǔn)確性和通用性。此方法不僅適用于日本地區(qū)電離層頻高圖的批量轉(zhuǎn)換,也適合不能被SAO Explorer軟件直接識(shí)別的一些數(shù)據(jù)和頻高圖圖像的轉(zhuǎn)換。2.電離層夜間增強(qiáng)現(xiàn)象的分析和理論解釋。實(shí)際運(yùn)用電離層頻高圖轉(zhuǎn)換方法對(duì)日本地區(qū)Wakkanai、Kokubunji、Yamagawa和Okinawa四個(gè)電離層探測(cè)站點(diǎn)2011年1月至2月期間垂直探測(cè)頻高圖轉(zhuǎn)換處理,獲取相應(yīng)地區(qū)電離層的特征參數(shù)和電子密度剖面。通過對(duì)獲取的四個(gè)站點(diǎn)電離層參數(shù)如電離層F2層臨界頻率(f0F2)以及虛高(hmF2)變化的分析,研究了日本地區(qū)夜間電離層異�，F(xiàn)象的特點(diǎn),并對(duì)其進(jìn)行了相應(yīng)的理論分析。本文分別對(duì)電離層午夜前和午夜后的增強(qiáng)現(xiàn)象進(jìn)行描述和物理機(jī)制的解釋。在對(duì)電離層午夜前增強(qiáng)現(xiàn)象統(tǒng)計(jì)分析時(shí)發(fā)現(xiàn)其表現(xiàn)出了緯向特征:緯度越高,增強(qiáng)出現(xiàn)的時(shí)間越早。也就是說,對(duì)于位在日本地區(qū)的四個(gè)站點(diǎn),增強(qiáng)現(xiàn)象最先出現(xiàn)在緯度較高的地區(qū)Wakkanai,然后增強(qiáng)逐漸向南移動(dòng),并被位于緯度最低的站點(diǎn)Okinawa最晚觀測(cè)到,同時(shí)我們初步對(duì)發(fā)現(xiàn)的這一現(xiàn)象給出了理論分析。
[Abstract]:The main result of ionospheric detection is to display it in the form of a frequency map. The acquisition of characteristic parameters and electron density profiles in the frequency map has been an important objective of ionospheric researchers. From these parameters and electron density profiles, the structure and state changes of the ionosphere can be roughly understood. In order to obtain the characteristic parameters and electron density profiles of the ionospheric frequency map in Japan, the ionosphere is analyzed and studied more deeply. In this paper, a method of converting the frequency map using digital image processing techniques is proposed, and then the local ionospheric anomalies at night are analyzed by using this method. The physical explanation of the trigger mechanism is given. The main contents are as follows:. 1. A new method of ionospheric frequency map conversion is proposed, which is optimized by using Radon transform and maximum inter-class variance method in image processing. The connected component marking method is used to enhance the phenomenon of fracture and weakening after noise filtering. Then, the echo trace amplitude information in the frequency height map is formatted and written to the SBF format file which can be recognized by the SAO Explorer software. Finally, the ARTIST algorithm is used to measure the converted frequency map automatically and to retrieve the electron density profile. The process of image processing and format conversion in this method is programmed as ionospheric frequency height map processing. Software. Using this software to analyze the frequency chart data of Okinawa ionospheric sounding station. The statistical comparison and analysis of the ionospheric F2 critical frequency obtained before and after the conversion of the frequency height map show that the proposed method has high accuracy and generality. This method is not only suitable for the ionospheric frequency in Japan. Batch conversion of high graphs. Also suitable for not being SAO. Conversion of some data and frequency map images directly identified by Explorer software .2.Analysis and theoretical explanation of ionospheric nocturnal enhancement phenomenon. Practical application of ionospheric height map conversion method to WA in Japan. Kkanai. Four ionospheric sounding stations, Kokubunji Yamagawa and Okinawa, were used to convert vertical sounding frequency patterns between January 2011 and February. The characteristic parameters and electron density profiles of the ionosphere in the corresponding region are obtained. The variation of the ionospheric parameters such as the critical frequency of the ionospheric F2 layer f _ 0F _ 2 and the virtual height of the ionosphere are analyzed. The characteristics of nocturnal ionospheric anomalies in Japan are studied. The enhancement phenomena before and after midnight in the ionosphere are described and the physical mechanism is explained. The statistical analysis of the enhancement phenomenon in the ionosphere before midnight shows that. Zonal characteristics:. The higher the latitude. The earlier the enhancement occurs, that is, for the four stations located in Japan, the enhancement occurs first in the higher latitudes of Wakkanai, and then gradually moves southward. It was observed at the lowest latitude station Okinawa at the latest, and a theoretical analysis of this phenomenon was given.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P352.7

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