Review plot of magnetic field variations (black line) for 13 March 1989. The black line represents one-minute variations of X, Y and Z magnetic field components for NRCan’s geomagnetic observatories. The observatories are ordered according to their geographic latitude, from the north (top) to the south (bottom). The color in the plot denotes geomagnetic activity where the activity is associated with the hourly range of magnetic field variations.