Fig. 2

North-south keogram from TRO and north-south (X) component of the magnetic field from the magnetometer network. Top panel shows a north-south keogram obtained from the AWI imager data for the period from 22:00 to 02:00 UT on March 8–9, 2013. In the bottom panel, the upper eight lines show the magnetic variations detected by the IMAGE magnetometer chain. The bottom line shows filtered data in the period range of Pi 2 pulsations (40–150 s) at AAB, which belongs to the MAGDAS/CPMN and is located at the magnetic equator. Three vertical dashed lines indicate the time when the front of the eastward-expanding auroral surges reached the zenith at TRO