中国大陆地电暴时频特征

The time-frequency characteristics of geoelectric storm in Chinese mainland

  • 摘要: 基于沿中国大陆两条经度链(118°E,99°E)、两条纬度链(40°N,34°N)的25个台站地电场分钟测量数据,分析了2014年8月至2016年8月共83次地电暴(磁情指数Kp≥5) 的波形特点,认为:地电暴可分为急始型、缓始型两类,一般持续1—3天;地电暴在广大区域同时发生,变化波形相同或相似,表现为明显的广域性特点.讨论了地电暴对地磁暴的变化响应以及不同台站和测道之间地电暴变幅的差异,认为地磁暴期间太阳风等引起的空间电磁场变化与地球介质相互作用激发大地电流产生变化,引起了地电场快变化和地磁场快变化的强烈响应,且地电暴变幅与台址地下介质电导率关系密切,电导率越小,变幅越大.用最大熵谱方法估算了地电暴的主要周期成分,按功率谱密度大小依次约为1.6 h,1 h,15 min,10 min等,而且不同地电暴的优势周期略有不同.

     

    Abstract: A total of 83 geoelectric storms (GESs) of Kp≥5 during the period of August of 2014 to August of 2016 are exhaustively analyzed by using the waveform analysis and maximum entropy estimation methods based on the minute-values of geoelectric field from 25 stations along two longitude chains (118°E and 99°E) and two latitude chains (40°N and 34°N) in Chinese mainland, and then the time-frequency variation characteristics of the geoelectric storm (GES) are studied in detail. As a result, the following understandings are obtained: there are two types of GESs, i.e., sudden commencement GES and gradual commencement GES, and they usually continue for one to three days; GESs synchronously occur in a wide area with the same or similar waveforms, suggesting a wide-area characteristic of GES. The response of the GES to the variation of the geomagnetic storm is discussed, and the differences in amplitude variation between different stations and in different directions are also discussed. It is believed that the interaction between the space electromagnetic field caused by the solar wind during the geomagnetic storm and the interaction of the Earth's medium causes a change in the ground current, which results in a strong response to the rapid change in the geoelectric field and the rapid change in the geomagnetic field. The amplitude of GES is related to the underground medium conductivity underneath the geoelectric field stations. The smaller the conductivity is, the lager the amplitude is. In general, the geoelectric storm principally has 1.6 h, 1 h, 15 min and 10 min periodic components according to the size of their power spectrum density, which have a little difference among different GESs.

     

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