The properties of two solar wind high speed streams and related geomagnetic activity during the declining phase of solar cycle 23

The ε parameter was calculated using both GSE and GSM coordinates. It was found that ε is ∼30% larger for GSM coordinates. Thus, the major cause of geomagnetic activity during HSSs is the large amplitude Alfvén waves but not coordinate transformations. Sector polarities (IMF By values) may be a secondary factor. However, other models, like the tilted solar dipole, should be considered as well.