Geomagnetic variations during periods of terrestrial magnetic field polarity reversals

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During periods of terrestrial magnetic field reversals the field intensity drops to about 1/10 of the current magnetic field strength. This raises the question which effects such a drastic change of the field magnitude may have on the current systems in the Earth ionosphere caused by magnetospheric dynamics. Ionospheric currents are the major contribution to the external part of the Earth magnetic field. At the present time such external contributions may reach up to 2000 nT at polar latitudes. However, on the average the external contribution amounts to about 1/100 of the internal magnetic field contribution of dynamo origin. Thus, the external part is usually very small compared to the internal part. At high latitudes, for example, the ground magnetic effect of the ionospheric currents is mainly due to the magnetic effect of the ionospheric Hall currents. During a polarity reversal the ionospheric Hall conductivity can significantly increase leading to an increased level of external magnetic field variations. First estimates indicate that the ratio external to internal magnetic field variations may well reach values of the order 1. It is the aim of the proposed study to analyze in detail the question of geomagnetic variations during polarity reversals of the geomagnetic field.