Plasma properties of superstorms at geosynchronous orbit: How different are they?

Plasma measurements at geosynchronous orbit are examined via superposed epoch analysis for various storm categories to assess whether superstorms have an unusually altered source population for the storm‐time ring current. It is found that certain characteristics of this near‐Earth plasma distribution during superstorms are similar to those of moderate or intense storms, or extensions of the trends seen in these lesser storms. These similarities include the dawn sector development of cold, dense plasma. However, other characteristics are unique to superstorms, such as the existence of cold, dense plasma at dusk and midnight. It is concluded that the ring current source during superstorms is a combination of the usual storm‐time characteristics as well as an unusually altered component.