Effect of sudden solar wind dynamic pressure changes at subauroral latitudes: Time rate of change of magnetic field

The observations obtained during the IMS from the IGS magnetometer chain extending from Cambridge, England, to Tromso, Norway are used to study the time rate of change of the magnetic field at subauroral latitudes at the time of interplanetary shock passages. The time rate of change of the H component maximizes in the high latitude dayside sector. For these typical interplanetary shocks, the dayside value of time rate of change can be as high as ∼ 3 nT/sec at Tromso and ∼ 1 nT/sec at York. The time rate of change in the dayside roughly depends on the change of square root of solar wind dynamic pressure. The largest of these time rates of change are similar to but slightly smaller than those known to cause disruptive disturbances in power distribution and communication systems. Thus, the daytime effects of sudden impulses may be equal to or greater than the nighttime effects associated with substorms as measured by their impact on terrestrial systems.