Geomagnetic Storm Sudden Commencements

Storm Sudden Commencements (ssc) 1868 to present: STORM1 and STORM2 Lists: (Some text here is taken from the International Association of Geomagnetism and Aeronomy (IAGA) Bulletin 39) 1868-1967 data (STORM1.SSC) are from IAGA Bulletin 33. These data are based on 3 observatories. Only one of them was at low latitude; the other two, with an invariant magnetic latitude of 50 degrees, were strongly sensitive to the auroral effect. 1968-1975 data (STORM2.SSC) are
from IAGA Bulletin 39. These data are much more reliable. The monthly reports from all observatories guarantee that very few events are omitted. With the examination of five low-latitude records, the changes of rhythm could be evaluated much better, and events were kept of rejected on a more rational basis. However, it is probable that, for statistical use, both lists will be relatively homogeneous. Indeed, Alibag was the low-latitude observatory of the 100-year list and
belongs, in the 1968-1975 list, to the group form which the amplitudes are close to the average of five observatories. 1976-1982 data are from IAGA Bulletin 32 series. These data are reduced in the same manner as the 1968-1975 data. 1983-present data are from the monthly ISGI Bulletins (DeBilt, Netherlands - 1983-1987 data; Institut de Physique du Globe, Paris, France - 1988-present data.