Ionospheric signatures of a Bursty Bulk Flow in the 6D Vlasiator simulation

Abstract. Bursty Bulk Flows (BBFs) are transient plasma flows in the Earth's magnetotail plasma sheet. These short-lived, high-speed flows play a key role in the magnetosphere-ionosphere coupling. Currently, most insights into the ionospheric signatures of BBFs come from individual case studies that include conjugate observations of BBFs in the magnetotail and field-aligned currents (FACs) in the nightside ionosphere. In this study, we utilise the 6D hybrid-Vlasov simulations to study the ionospheric signatures of BBFs in the near-Earth magnetotail. We show that a BBF with Vx≥400 km s−1 emerges shortly after magnetic reconnection occurs on the duskside at a radial distance between 11 and 14 RE (where RE=6371 km is the radius of the Earth) in the current sheet. As the BBF moves Earthward, clockwise (counterclockwise) flow vortices are induced on its dawn (dusk) sides. These vortical flows generate FACs flowing upward (out of the current sheet) on the dawnside and downward (into the current sheet) on the duskside flank, respectively. The mapping of BBF structures onto the ionosphere shows that the structure is primarily aligned in the east-west direction, with its ionospheric signatures appearing as enhancements in FACs, ionospheric conductances, horizontal ionospheric currents, energies of precipitating electrons and protons, and the formation of localised plasma flow channels. The upward and downward FACs associated with BBFs in the magnetotail consistently map to enhanced Region 2 (R2) and Region 1 (R1) FAC structures at ionospheric altitude, which are then closed in the ionosphere by north-west flowing Pedersen currents. The ionospheric counterpart of the Earthward plasma flow of the BBF is a channel of equatorward plasma flow, while the westward drift of these enhanced structures corresponds to the duskward motion of the BBF in the magnetotail.