Statistics of extreme geomagnetically induced current events

Abstract

In this work, space weather events associated with extreme geoelectric field and geomagnetically induced current (GIC) magnitudes are investigated. The geoelectric field and consequent GIC are computed using geomagnetic field recordings over an extended time period and ground conductivity and technological system configurations favorable for large GIC. The statistics are derived for both overall occurrence of the geoelectric field and geoelectric field occurrence conditioned by the state of the magnetosphere and the solar wind. It is shown that in high‐latitude areas having resistive ground conductivity structures and in systems having characteristics favorable for large GIC, GIC amplitudes of about 200 A can be expected to occur 102–103 times (in 10‐s values) per year while GIC of about 2000 A occur only 10–100 times in 100 years. On the basis of the Dst index and the solar wind electric field values derived by Siscoe et al. (2006) and Tsurutani et al. (2003), it is estimated by means of derived conditional probability distributions that although magnitudes of about 10 V/km are possible, the most probable value for the maximum magnitude of the geoelectric field during the Carrington event of 1–2 September 1859 is about 4 V/km. The usage of derived conditional probabilities in space weather applications is also discussed.