Statistical study of Field-Aligned Currents in the Ionosphere associated with Bursty Bulk Flows Events

Bursty bulk flows (BBFs) are fast plasma flows in the central plasma sheet. These BBFs couple to the high-latitude ionosphere through field-aligned currents (FACs). A statistical study of FACs associated with BBF events at the BBF ionospheric footpoint in both hemispheres has been lacking. We analyzed single spacecraft FACs from Swarm A and B during a dataset of BBF intervals and compared to 200 different random datasets selected within the same years and months and geomagnetic conditions as the BBFs. Our results show that in the Southern Hemisphere, the probability of observing large FACS (80th percentile) is significantly greater during BBFs compared to random chance. This is valid around the typical BBF footpoints according to the mapping of thousands of BBFs. However, in the Northern Hemisphere, the larger FAC values do not coincide with the BBF-mapped region suggesting an inter-hemispheric asymmetry.