Scatter in the plots of Dst(min) versus Bz(min)

摘要

In the plots of -Dst(min) versus -Bz(min) in cycle 23, in restricted ranges of -Dst(min), there was lot of scatter and the correlations were low. A bivariate analysis using geomagnetic -Dst(min) and auroral AE index did not improve the situation. Substitution of -Dst(min) by the ram-pressure-corrected true ring current Dst~*(min) improved the correlations only slightly. Using the product VBz instead of Bz(min) as a proxy for magnetospheric energy input did not improve the correlations, even for the 12 severe storm events in cycle 23. A multivariate analysis using -Bz(min) versus - Dst(min), with All, AL and auroral particle precipitation index POES as additional indices improved the correlations and reduced the scatter. It was noticed, however, that for these severe storms, a major part of the solar wind input energy (～85%) was still going to the Dst ring current, but this had an uncertainty of ～15%. So in any severe storm event, the ring current could receive anything from 70% to 100% of the solar wind input energy.