Resolution No.6 (2009): SC/SI/SSC determination

IAGA, recognising the importance of the list of storm sudden commencements (SSC), continuous since 1868, to the worldwide scientific community, appreciating the efforts of the Ebro, Spain magnetic observatory in regularly maintaining and circulating the up-to-date list of events, noting

• that the definitions of storm commencements (SC), sudden impulses (SI), and SSC have changed over time, reflecting better understanding of physical processes and changes in instruments and working practices,
• that a new method, relying on quantitative criteria for SC/SI/SSC determination, has been proposed by the Ebro team and published by J. J. Curto, T. Araki, and L. F. Alberca (Evolution of the concept of Sudden Storm Commencements and their operative identification, Earth Planets Space, 59, I- XII, 2007), and is to be described in a revised IAGA Guide for Geomagnetic Indices,
• that this method is well-defined and reproducible and that it produces data that are consistent with data produced using the existing method developed by P.N. Mayaud,

endorses the use of this new method as the basis for the future determination of SC/SI/SSC, and calls for Ebro observatory to adopt the method in providing its list of published events.