Auroral Streamers as Ionospheric Footprints of Bursty Bulk Flows

In-situ measurements in the magnetotail are sparse and limited to single points. In the ionosphere, on the other hand, there is a broad range of observations, including magnetometers, aurora imagers, and radars. Since the nightside ionosphere is to some extent the projection of the magnetotail plasma sheet, it can be used as a monitor of the dynamics of the tail.  In order to interpret the ionosphere and ground observations properly it is fundamental to understand the coupling process between the ionosphere and the magnetosphere. Here, we use the global magnetohydrodynamic simulation model, OpenGGCM-CTIM-RCM, to investigate such a coupling process. 

We find that Bursty Bulk Flows (BBFs) are identifiable in the simulation as ionospheric auroral streamers, and  are an important processes that greatly contributes to convection of the tail. In this paper, we map flows from the magnetotail to the ionosphere along magnetic field lines. We consider  three states of the magnetotail: immediately before substorm onset, during substorm expansion, and during a steady magnetic convection event. We find that the streamers are north-south aligned in midnight sector, and they have more east-west orientation in the dawn and dusk regions. The tail and the ionosphere activity increase during SMC event compared to the pre-onset and quiet times.