Average characteristics are determined for 74 great magnetic storms
with sudden commencements that occurred in 1902-1945. The storm field is
resolved for different epochs of storm time into tv;o parts: (i) Dst, which
is independent of local time, that is, of longitude A, relative to the sun,
and (ii) DS, which depends on A . They are obtained, for each of the three
magnetic elements, declination, horizontal force, and vertical force, at
eight geomagnetic latitudes ranging from 80°N to 1°S. DS is harmonically
analyzed; the first harmonic component is shown to be the main component of
DS. The storm-time course of this component is compared with that of Dst;
DS attains its maximum earlier and decays more rapidly. The results of the
analysis of great storms are compared with those for weak and moderate
storms that were reported previously. Some characteristics of Dst change
with intensity. Except in magnitude, main characteristics of DS are independent
of intensity.The research reported in the document has been sponsored
by the Air Force Cambridge Research Center, Air Research
and Development Command, under Contract No. AF 19(604)-2163.LIST OF TABLES -- LIST OF FIGURES -- ABSTRACT -- 1. INTRODUCTION -- 2. OBSERVATORIES -- 3. STORM-TIME VARIATIONS : 3.1 Dst in the geomagnetic-north component, Hgm ; 3.2 Dst in the geomagnetic-east component, Egm ; 3.3 Dst in the vertical force Z -- 4. DISTURBANCE DAILY VARIATIONS -- 5. FIRST HARMONIC COMPONENT OF DS -- 6 . HIGHER HARMONIC COMPONENTS OF DS AND SD -- 7. COMPARISON OF Dst AND DS -- 8 . SEASONAL VARIATIONS IN Dst : 8.1 Seasonal variation in Dst(H); season d and season j ; 8.2 Seasonal variation in Dst(H); season e and season s -- 9. SEASONAL VARIATIONS IN DS -- 10. CONCLUSION -- 11. ACKNOWLEDGEMENTS -- REFERENCESYe
