How the K index

of geomagnetic activity helps to assess the data amount for

magnetotelluric soundings



Institute of

Geophysics, Polish Academy of Sciences


Magnetotellurics (MT) is a passive sounding

method to investigate the subsurface distribution of electric

conductivity which allows to draw conclusions on underlying rocks,

geology, and tectonics. A conductivity model depends on MT transfer

functions as input data. Transfer functions (TF) are obtained via

statistical methods from variations of natural electromagnetic signals

which constitute the source signals in MT. In this way the quality,

stability, and smoothness of TFs depend on both geomagnetic activity

(i.e., the strength of the source signal) and the data amount used in

the statistics. However, it is impossible to quantify both influences

on TFs without having separated them before. Such a separation has

been untertaken in the presented study by means of a Polish long-term

MT dataset and the K indices in Belsk observatory. As a result the

influences of both parameters become systematic and plausible, and

some erroneous assumptions encountered in the MT community could be