Time-delay interrelation between geomagnetic activity variations and sunspots: the Ohl effect Original Research Article

Day-to-day geomagnetic field variations recorded in St. Petersburg since 1841 could be used not only to restore a history of geomagnetic storminess and large-scale solar magnetic fields in the past but also predict the sunspot cycles. Ohl found close relationships existing between geomagnetic activity variations during declining phase of the solar cycle and the next sunspot maximum. We have determined those recurrent geomagnetic activity variations which contribute mostly the current sunspot activity. According to the Ohl correlation scheme and a periodicity found early in the geomagnetic records (Bruckner cycle) the current sunspot cycle 23 is expected to be similar to solar cycle 20. The maximum of the solar cycle 23 was survived in July 2000.