Geomagnetic Sudden Commencements
Rapid Magnetic Variations
(Storm) Sudden Commencements (ssc) are defined
by an abrupt increase or decrease in the northward component of the
geomagnetic field, which marks the beginning of a geomagnetic storm
or an increase in activity lasting at least one hour. The sudden
commencements and solar flare effects (sfe) are
from magnetograms of the worldwide network of magnetic observatories.
The stations, together with their abbreviations, are given in the
series IAGA Bulletin No. 32 which contains the yearly compilation of
these data. Before January 1966 these reports were published
periodically in Journal of Geophysical Research. From then until 1970
they were published quarterly in
Beginning with December 1970, these data are published monthly and, thus, are
based on fewer reports and differ slightly from similar data published
previously. The decision to publish this less complete report was made in
order to make the data available more rapidly. Only events reported by at
least five observatories are reported.
The latest ssc reports
are provided by Observatorio del Ebro, Roquetes, Spain, on behalf of
the IAGA Service on Rapid Magnetic Variations.
For questions concerning specific data or the contents of this page,
Last modified: 29 Apr 1997