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The Average Morphology of Geomagnetic Storms with Sudden Commencement

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[Technical Report, Technical Report]

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The average morphology is described of geomagnetic storms with sudden commencement. A numerical intensity index was assigned to each of 346 storms occurring in 1902-1945. On the basis of these indices the storms were divided into three sets, of 136 weak, 136 moderate, and 74 great storms. Their morphology was studied separately. For weak storms records were analyzed from 26 magnetic observatories, ranging in geomagnetic latitude from 80 deg N to 48 deg S and for moderate and great storms, from 19 observatories, 80 deg N to 1 deg S. The stormtime variation Dst and the disturbance longitudinal inequality DS were determined for the first three storm days for different latitudes. The DS variation was obtained, and harmonically analyzed, for each of the first 8 quarter-day intervals and for the succeeding three 8-hour intervals. New features of storm morphology during the first few hours of storm time were discovered namely, that DS reaches its maximum in about two or three hours from the storm commencement, and that its phase rapidly changes during the first few storm hours.


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  • Meteorology

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[A, Approved For Public Release]