甘肃嘉峪关、瓜州地电场日变化与地电暴差异机理分析

Diurnal Variation and Mechanism of Differences inGeoelectric Storms in Jiayuguan and GuazhouGeoelectric Fields, Gansu Province

摘要:

通过甘肃省嘉峪关台地磁场观测资料，研究嘉峪关台、瓜州台磁静日地电场日变化的时频特征波；由地电场分钟值观测数据的时序叠加残差方法，研究嘉峪关、瓜州山的地电暴变化。结果表明：（1）两台地电场静日变化以两次起伏变化为主，无相位差，但两台之间日变幅差异较大；（2）地电场分量变化与地磁场正交分量变化显著相关；地电场与地磁场日变波形不同，极值时间有差异。2个台存在很明显的高频成分，在去除了高频变化后，其优势周期也相同，从大到小依次为12 h、8 h、24 h。地磁场H分量因存在磁暴影响，故高频变化较多，在去除了磁暴影响后，其优势周期从大到小依次为24 h、12 h、8 h；（3）当电磁暴扰动剧烈时，两台可以较清晰地记录到地电暴的完整变化。在发生电磁暴时，地电场与地磁场的相关性明显降低，且不同台、不同测向之间的变化幅度也不尽相同。两台东分量E_Y暴日的日变幅较静日明显增大，磁暴期间Y分量变化率与地电场东分量E_Y观测数据显著相关，由此说明：两台日变幅的不同与台站台址电导率有关，太阳风引起的电离层活动是引起了地电场日变化主因。引起电暴的原因可能不同于引起日变化的原因，主要是两台之间及不同测向之间的浅、深层电阻率和地质构造等诸多因素的结果。

Abstract:

Diurnal variations in the geoelectric field at Jiayuguan and Guazhou stations are studied using the observation data of the geomagnetic field at Jiayuguan Station in Gansu. Changes in geoelectric storms are explored with the method of time-sequence superposition residual. Results show that (1) the static diurnal variations in the geoelectric field at the two stations appear as two obvious undulating changes without a phase difference, and the ranges of diurnal variations at the two stations are different. (2) The component variation in the geoelectric field is significantly correlated with the orthogonal component variation in the geomagnetic field. The waveforms of diurnal variation in geoelectric and geomagnetic fields are different. The dominant periods of the two stations are 12, 8, and 24 h after the high-frequency change is removed, and the dominant periods become 24, 12, and 8 h after the geomagnetic storm effect is eliminated. (3) During an electromagnetic storm, the correlation between geoelectric and geomagnetic fields is obviously reduced. During a magnetic storm, the change rate of Y is significantly correlated with E_Y of the geoelectric field. This result indicates that the differences between daily variations in the two stations are related to the underground conductivity of station sites. The diurnal variation in the geoelectric field is mainly caused by solar wind-induced ionospheric activity. A geoelectric storm may be attributed to many factors, such as shallow and deep resistivities and geological structures between the two stations.