Interference effects of aircraft on the Earth's electromagnetic response at Very Low Frequency and Low Frequency
2015 (English)In: Geophysical Prospecting, ISSN 0016-8025, E-ISSN 1365-2478, Vol. 63, no 1, 211-224 p.Article in journal (Refereed) Published
Very Low Frequency (VLF) electromagnetics (EM) has been widely and successfully applied in mineral exploration and ground water exploration in the past decades. Many radio transmitters with strong signal to noise ratios are scattered in the Very Low Frequency (VLF) band and the Low Frequency (LF) band. Based on the experiences gained from ground measurements with the Radio Magnetotelluric (RMT) technique operating in the frequency interval 1-250 kHz, broad band magnetometers have been utilized to cover both the VLF (3-30 kHz) and LF (30-300 kHz) bands to increase the resolution of the near surface structure. The metallic aircraft as a conductive body will distort the magnetic signal to some extent, and thus an investigation of the interference of the aircraft on the electromagnetic signal is important. Noise studies due to the rotation of the aircraft and the aircraft itself as a metallic conductive body has been carried out by three different methods: 3D wave polarization, determination of transmitter direction and full tipper estimation. Both VLF and LF frequency bands were investigated. The results show that the magnetic field is independent of the aircraft at low frequencies in the VLF and part of the LF bands (below 100 kHz). At high frequencies (above 100 Hz), the signals are more influenced by the aircraft and the wave polarization directions are more scattered as seen when the aircraft turns. Some aircraft generated noise which is mixed with the radio transmitter signals are detected as 'dummy' signals by the 3D wave polarization method. The estimated scalar magnetic transfer functions have dependence on the aircraft flight directions at high frequencies which is caused by the aircraft interference. The aircraft eigen response in the transfer functions (tippers) between vertical and horizontal magnetic field components can be compensated for in the real part of the estimated tippers, but some unknown effect is still observed in the imaginary parts.
Place, publisher, year, edition, pages
European Association of Geoscientists and Engineers, 2015. Vol. 63, no 1, 211-224 p.
Airborne Electromagnetics, Noise, Signal processing
Research subject Geophysics with specialization in Solid Earth Physics
IdentifiersURN: urn:nbn:se:uu:diva-229914DOI: 10.1111/1365-2478.12149ISI: 000346898400017OAI: oai:DiVA.org:uu-229914DiVA: diva2:738248