Superposed epoch study of PV 5/3 during substorms, pseudobreakups and convection bays

We present a superposed epoch study to examine the entropy parameter PV 5/3 , for isolated substorms, pseudobreakups and convection bays observed by Geotail in the near‐Earth plasma sheet, by using a flux‐tube‐volume formula with coefficients adjusted to fit magnetic field models for a variety of conditions. It is found that the changes of PV 5/3 for these three types of events are distinct: (1) for substorms, PV 5/3 increases continuously during the growth phase, decreases after dipolarization, and maintains a low value of ∼0.08 nPa(R E /nT) 5/3 ; (2) for pseudobreakups, PV 5/3 changes in a way similar to substorms, but decreases more moderately and then gradually increases; (3) for convection bays, PV 5/3 takes a nearly constant value of 0.06 nPa(R E /nT) 5/3 . These results suggest that the characteristics of the processes that violate conservation of PV 5/3 play a central role in the temporal and spatial reduction of PV 5/3 and thus determine the earthward plasma transport during active times.