H.: Modelling of geomagnetic induction in pipelines

Abstract. Geomagnetic field variations induce telluric cur-rents in pipelines, which modify the electrochemical condi-tions at the pipe/soil interface, possibly contributing to cor-rosion of the pipeline steel. Modelling of geomagnetic in-duction in pipelines can be accomplished by combining sev-eral techniques. Starting with geomagnetic field data, the geoelectric fields in the absence of the pipeline were calcu-lated using the surface impedance derived from a layered-Earth conductivity model. The influence of the pipeline on the electric fields was then examined using an infinitely long cylinder (ILC) model. Pipe-to-soil potentials produced by the electric field induced in the pipeline were calculated us-ing a distributed source transmission line (DSTL) model. The geomagnetic induction process is frequency dependent; therefore, the calculations are best performed in the fre-quency domain, using a Fourier transform to go from the original time domain magnetic data, and an inverse Fourier transform at the end of the process, to obtain the pipe-to-soil potential variation in the time domain. Examples of the model calculations are presented and compared to observa-tions made on a long pipeline in the auroral zone. Key words. Geomagnetism and paleomagnetism (geo-magnetic induction)