电离层频高图转换方法及应用研究

发布时间：2018-01-26 04:51

本文关键词： 频高图图像处理反演夜间增强　出处：《武汉大学》2017年硕士论文　论文类型：学位论文

【摘要】：电离层探测得到的主要结果是以频高图的方式显示,获取频高图中的特征参数和电子密度剖面一直以来都是电离层研究工作者的重要目标。从这些参数信息和电子密度剖面可以大概了解电离层的结构和状态变化,进而更加深入地对电离层进行分析和研究。为了准确获取日本区域电离层频高图中的特征参数和电子密度剖面,本文提出了一种利用数字图像处理等技术对频高图进行转换的方法,然后运用此方法对当地电离层夜间的异常现象进行分析,并给出触发机制的物理解释。主要内容包括:1.提出了电离层频高图转换的一种新方法。利用图像处理中的Radon变换和最大类间方差法对频高图滤噪优化,并运用连通分量标记法对滤噪后出现的断裂和弱化现象进行增强;然后对频高图中的回波描迹幅度信息格式化,写入到可以被SAO Explorer软件识别的SBF格式文件中;最后运用软件自带的ARTIST算法对转换后的频高图进行自动度量和电子密度剖面的反演。将此方法中的图像处理和格式转换过程编写为电离层频高图处理软件。运用此软件对Okinawa电离层探测站点的频高图数据进行实例统计分析,对频高图转换前后度量得到的电离层F2层临界频率f0F2统计对比分析。结果表明该方法具有较高的准确性和通用性。此方法不仅适用于日本地区电离层频高图的批量转换,也适合不能被SAO Explorer软件直接识别的一些数据和频高图图像的转换。2.电离层夜间增强现象的分析和理论解释。实际运用电离层频高图转换方法对日本地区Wakkanai、Kokubunji、Yamagawa和Okinawa四个电离层探测站点2011年1月至2月期间垂直探测频高图转换处理,获取相应地区电离层的特征参数和电子密度剖面。通过对获取的四个站点电离层参数如电离层F2层临界频率(f0F2)以及虚高(hmF2)变化的分析,研究了日本地区夜间电离层异常现象的特点,并对其进行了相应的理论分析。本文分别对电离层午夜前和午夜后的增强现象进行描述和物理机制的解释。在对电离层午夜前增强现象统计分析时发现其表现出了纬向特征:纬度越高,增强出现的时间越早。也就是说,对于位在日本地区的四个站点,增强现象最先出现在纬度较高的地区Wakkanai,然后增强逐渐向南移动,并被位于纬度最低的站点Okinawa最晚观测到,同时我们初步对发现的这一现象给出了理论分析。
[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.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P352.7

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