Tippers at island observatories: Can we use them to probe electrical conductivity of the Earth's crust and upper mantle?

Abstract

For decades, time series of hourly‐mean values of the geomagnetic field measured on a global network of observatories have been routinely used to recover the electrical conductivity distribution in midmantle depths. Nowadays, most observatories provide data in the form of minute‐means. This allows for analysis of short‐period geomagnetic variations, which, in principle, contain information about geoelectric structures in the crust and upper mantle. However, so far these data have been ignored for induction studies of the Earth due to a theoretical preconception. In this paper, we demonstrate that short‐period responses (tippers) at island observatories, being large owing to the ocean effect, are also sensitive to 1‐D structures and thus can be used for probing the Earth. This means that a huge amount of data that was not exploited hitherto for induction studies should be reconsidered as a useful source of information about geoelectric structures in oceanic regions where our knowledge is still very limited.