engleski

The 100 Largest Geomagnetic Storms in the Last 150 Years

geomagnetic storms, we have created a ranked list of the 100 largest geomagnetic storms in the period 1868‐present. The selection and ranking is based on the aa‐index and a set of single geomagnetic observatory data with long records. For these events, available historical data such as sunspot records, flare observations, neutron monitor data, in situ solar wind data and various geomagnetic measures, has been collected and analyzed. For a very large majority of the events, the erupting active region at the Sun has been identified, as well as the time of the major eruption associated with the storm. The characteristics of geomagnetic records and solar wind in situ measurements have been compared statistically to less intense storms, and it is found that the extreme storms are in general more complex, displaying several storm peaks. The large majority (>90%) of the extreme storms are further associated with one or several shocks as indicated in the geomagnetic records by observed storm sudden commencements. Most of the events occur in spring or fall season. For all events in the time period where neutron monitor data is available they display Forbush decreases, mostly complex with several substructures. Ground Level Enhancements (GLEs) indicating intense Solar Energetic Particle (SEP) events are, on the other hand, only present in ~20% of the events. The presented work has received funding from the European Union Seventh Framework Programme (FP7/2007‐2013) under grant agreement no 263252 [COMESEP] .

sunspots ; solar flares ; geomagnetic storms ; cosmic rays

nije evidentirano