Relationships for predicting magnetic cloud-related geomagnetic storm intensity

Studying geomagnetic storm activity during 135 interplanetary magnetic cloud periods from 1965 to 1998, Wu and Lepping (J. Geophys. Res. 107 (2002b) 1346) found that the storm Dst index correlated well with both the interplanetary magnetic field z-component (B-z) and the "rectified" electric field VBs but did not correlate well with solar wind speed. It is shown that the role of magnetic cloud speed in predicting storm intensity is a minor one. It also was found that the correlation coefficient for Dst vs. B, increases dramatically when the solar wind speed exceeds 600 km/s. This implies that solar wind speed is also important indirectly for predicting the storm intensity when using B-z (or VBs) as a direct predictor. Using the same data set of 135 magnetic cloud-associated storms, two Dst prediction-relationships were developed: one is velocity independent and the other is velocity dependent. In this study, (i) both Dst prediction-relationships will be presented and (ii) some recent storm events will be presented and discussed by (as examples) using both Dst prediction-relationships. The results of this study also show: (1) The intensity of a magnetic storm which is associated with a magnetic cloud is predictable. (2) The prediction relationships for storm intensity, Dst(min) are: Dst(min) = 0.83 + 7.85 x Bz(min) and Dst(min) = -16.48-12.89 x (VBs)(max). (3) The velocity dependence of the Dst(min) prediction relationship will improve the accuracy for a Bz-base prediction result. (4) For the VBsmax-based prediction relationship, the prediction accuracy of Dst(min) becomes worse when a velocity-dependent prediction relationship is used. (C) 2004 Published by Elsevier Ltd.