Variation of geoelectric pulse energy spectra on the northeastern margin of Tibet Plateau

The geomagnetic pulsation, which is in the period of 0.2-600 s and appears at a particular moment, is an important component of the geomagnetic field. However, there is no uniform understanding about the ultra-low frequency (ULF) components of the geoelectric field and how is it changing, the main reason is perhaps the lack of the observation data to support study. In the paper, we calculate cross-correlation function of two signals based on the geoelectric field data with ultra-low frequency (1 Hz) from five observation stations around northeastern margin of Tibet Plateau since 2015. Consequently, the most uncorrelated electromagnetic disturbance may be suppressed. By the way of high pass filter, frequency spectrum, auto-power spectrum and cross-power spectrum of the signals, the result show that the sampling data in the frequency band of 10^-3-10^-1 Hz perhaps contains geoelectric pulsation signal. At the same time, through comparison with the analytical result of the relevant frequency bands of the geomagnetic field, we draw the conclusion that the geoelectric field within the frequency band 10^-3-10^-1 Hz shows the characteristics of the P_c3-5, in addition, the 10^-3-10^-1 Hz frequency band had the largest spectrum. This phenomenon may be related to the stability of the magnetosphere and the ionospheric radiation.