Fast magnetotail plasma sheet flows and field aligned currents

The magnetic connection between the ionosphere and the magnetotail current sheet allows for couplings between ionospheric conditions and various phenomena in the magnetotail. Magnetic reconnection in the tail causes fast plasma flow channels that affect the field-aligned currents (FACs) flowing between the tail and the ionosphere. It is currently understood that these plasma flows in the tail result in ionospheric current channels that correspond predominantly to North-South aligned auroral structures called streamers.  

We investigate the effects to the FAC systems by making a comprehensive survey of fast plasma sheet flows in the magnetotail and mapping the events to the ionosphere above Fennoscandia, using the T89 magnetic field model. The survey is done for Cluster-, MMS-, and THEMIS-mission data archives between the years 2001 and 2025. The criteria for fast flows are those commonly used for bursty bulk flows; velocity over 400 km/s in the Earthward direction and plasma beta over 0.5 to ensure the satellite is within the plasma sheet. We then utilise the Spherical Elementary Current System (SECS) method with the IMAGE magnetometer network to obtain ionospheric equivalent current densities and estimates of changes to FACs. Where possible, we analyse optical data, and compare auroral structures to the ionospheric current patterns. Studying the signatures of plasma sheet flows from ground-based observations as well as satellite data helps in building a better understanding of the connection between the two domains.