(a) TEC map as well as the ionospheric convection pattern around 18:22 UTC on 17 March 2015. The orbital track of Swarm A is indicated by the magenta dashed line. (c) In situ measurements from Swarm A from 18:07 to 18:32 UTC, and the panels from top to bottom are the total number of tracked GPS satellites, ROTI, in situ electron density and temperature, as well as the small-scale FACs signatures (<150 km). (c) and (d) are in a similar format as for (a) and (b), but for Swarm B measurements around 18:52 UTC.