Temporal development of equivalent overhead current density profile at Uppsala (Lövö) magnetic longitude. At the left latitude scale the latitudes of a few relevant observatories are marked. Westward currents are marked by red colours in shades to indicate current intensities. Eastward currents by blue colours. The curve in full black line displays PCN index values with their scale to the right. The white diamonds indicate events of magnetic variations steeper than 10 nT/s. The dashed broken line indicates movements of current systems. The black triangle marks the power line cut.