Spacecraft Signatures of Bursty Bulk Flows and Dipolarizing Flux Bundles

Abstract:

Bursty Bulk Flows (BBFs) and Dipolarizing Flux Bundles (DFBs)are commonly observed in the plasma sheet during all types of geomagnetic activity, but they are more common during geomagnetically active times. The typical features are high earthward plasma speed, a rapid change of the magnetic field towards a more dipolar orientation, and a decrease in plasma density, to name a few. BBFs and DFBs are of limited width of the order of a few RE; however, their size distribution is not well constrained because of the limited data. Global MHD simulation have reproduced virtually all of the macroscopic features of BBFs and DFBs. Those simulations also show evidence of remarkable dynamic behavior such as snake-like flows, sideways motion, and DFBs bouncing back from the inner magnetosphere. Here, we present OpenGGCM simulations of BBFs and DFBs during times of varying geomagnetic activity. The simulations indicate that s/c signatures of BBFs and DFBs are not unique but depend on how the s/c encounters the structure. In particular, a s/c can encounter a DFB or BBF in a way by which some of the typical signatures do not show up. Based on the simulations we will present a classifications of possible s/c signatures and show examples that demonstrate how they come about.