Working Meeting - St. Patrick's Day geomagnetic storm: a big GIC event?

Ari Viljanen (FMI)
Thursday, 26th 17:00 - 18:30, Delvaux

As quantified by several activity indicators, the largest geomagnetic storm during the solar cycle 24 until now occurred on 17-18 March 2015. The planetary Kp index reached the value of 8-, the NOAA Scale for geomagnetic storms reached G4, estimated daily Ap was 108, and the provisional AE index exceeded 2000 nT. When compared to large events of previous solar cycles, the March 2015 case still seems quite modest. For example, the daily magnetic Ak index at Nurmijärvi, South Finland, was 174 which is only the top 32 value since 1953. However, model calculations of geomagnetically induced currents (GIC) in Finland indicate that this event was locally comparable to the Halloween storm in October 2003. We invite observations and/or model results especially of the geoelectric field and GIC from other regions to find out how significant this event was at the global scale when compared to previous severe storms.