Relationship between the geomagnetic Dst(min) and the interplanetary Bz(min) during cycle 23

In cycle 23 for geomagnetic storms of -Dst(min) > 50 nT, the plot of -Dst(min) versus -Bz(min) for the low -Bz(min) range 0-10 nT showed erratic variation in Dst(min), (correlation 0.19). Even for -Bz(min) range 10-20 nT, -Dst(min) values had considerable scatter (correlation 0.57). For -Bz(min). > 20 nT, the relationship was good (correlation 0.82). For the whole range -Bz(min) 0-50 nT, the correlation was high (0.88). Thus, if -Bz(min) is very large (similar to 20 nT), large -Dst(min) occurs but in a wide range of 100-500 nT. (C) 2009 Elsevier Ltd. All rights reserved.