STATISTICAL CHARACTERISTICS OF BURSTY BULK FLOW EVENTS

Using a common methodology to analyze data from the AMPTE/IRM and ISEE 2 satellites we report on the statistical properties of bursty bulk f low events (BBFs) in the inner plasma sheet (IFS). A positive correlat ion between BBFs and the AE index suggests that BBFs are predominantly geomagnetically active time phenomena. Earthward BBFs are more freque nt close to midnight and away from Earth, up to a distance of similar to 19 R(E). Tailward BBFs are very infrequent in the IRM data set and somewhat less infrequent in the ISEE 2 data set in the region of the s atellites' spatial overlap, possibly due to the more active conditions prevailing during the ISEE 2 mission in that region. However, in both data sets the ratio of tailward to earthward BBFs increases with dist ance from Earth; more than 20% of all BBFs are anti-sunward tailward o f X = -19R(E) in the ISEE 2 data set. BBFs are responsible for 60-100% of the measured earthward transport of mass, energy and magnetic flux past the satellite in the regions of maximum occurrence rate, even th ough they last approximately 10-15% of the IFS observation time there. Thus BBFs represent the primary transport mechanism at those regions. The one-to-one correspondence between BBFs and substorm phase, as wel l as the relative contribution of BBFs to the total transport observed during substorms are questions that await further investigation based on multi instrument studies of individual events.