Relationship between electric field and currents in the ionosphere and the geomagnetic Sq field

[1] Relationships of the geomagnetic Sq field to the electric field, conductivity, and currents in the ionosphere were studied from the correlation of the Sq amplitude in the Y-component with that of the ionospheric electric field and Hall currents. The electric field was obtained from the observation by the MU radar from 1989 to 2001, and the currents were estimated from the obtained field and the conductivity calculated by using the electron density profile obtained from the IRI 90 model. Estimated daily amplitude of the ionospheric Hall currents fairly well explains that of the Sq field. It was shown that variation of the Sq amplitude is mainly caused by the local ionospheric conductivity even if the variation is treated by each season separately. Another interesting feature is that the Sq amplitude tends to be small in winter for the same estimated Hall ionospheric currents. This is caused either by the seasonal variation of Hall conductivity to the Pedersen conductivity causing the variation of the contribution of the Hall currents to the total currents or by the asymmetry of the neutral wind through the magnetic effect of the ionospheric currents driven by the wind or of the field-aligned currents flowing between the both hemispheres driven by the asymmetric dynamo action in the ionosphere.