Sudden changes, called impulses, in the rate of magnetic secular variations often occur simultaneously at many observatories. These impulses have raised questions about the electrical conductivity of the outer core and mantle and about the possible transmission of relatively short period magnetic variations from the core to the surface. It is shown that the impulses in the horizontal component of the magnetic field correlate with the sunspot cycles and therefore are most likely caused by changes in external sources such as the ring current and equatorial and polar electrojets.