Magnetotelluric (MT) field data contain natural electromagnetic signals and artificial noise sources (instrumental, anthropogenic, etc.). Not all available time-series data contain usable information about the electrical conductivity distribution at depth, particularly when the signal-to-noise ratio (SNR) is low. Geomagnetic storms represent temporary disturbances of the Earth's magnetosphere caused by solar wind-shock wave interacts with Earth's magnetic field. The variation of the electromagnetic signal increases dramatically in the presence of a strong geomagnetic storm. Using the data observed during a strong geomagnetic storm may overcome the locale noise and bring a reliable MT impedance at contaminated sites. Three case studies are presented to show the positive effect of geomagnetic storms on MT field data. A more reliable and interpretable impedance calculated from a survey line contaminated by strong noise is obtained using the data observed during a strong geomagnetic storm.
