A study of ionospheric impacts in the wireless electromagnetic exploration with the QWE method

Abstract

AbstractThe wireless electromagnetic method (WEM) is an emerging new method for deep resource exploration. This method, based on magnetotellurics and the controlled-source electromagnetic method, features advantages such as high signal strength and signal-to-noise ratio, large penetration depth, and easy survey geometry setups, which gives WEM potential for deployment in mineral exploration of large depths. As for now, there is little research into the controlling factors of the ionosphere in WEM exploration, and whether the ionosphere is related to the modeling result remains unclear. In this work, we first developed a modified quadrature with extrapolation (QWE) method to settle the oscillation in the calculation of a WEM response. Then we compared its performance and accuracy with other methods and find that our method has better numerical stability even with highly oscillated integral kernels, which is ideal for WEM emulation. With the emulation tools, we can further investigate how the ionosphere’s height and resistivity affect the ground-received signal. We compared signals obtained with different ionospheric properties under various earth resistivity models. The conclusion is that these ionospheric properties only impact the received signal’s strength and have no influence on the Cagniard resistivity or phase of impedance.