Recovery of data on interplanetary medium parameters based on the <Emphasis Type="Italic">aa</Emphasis> index of geomagnetic activity

The average annual values of the electric field and parameters of the solar wind and IMF from our time to 1868 have been estimated based on the statistical relation between the aa index of geomagnetic activity and the interplanetary medium parameters. This estimation indicates that the relative variations during the 20th century were observed in the electric field (25 ± 3%), the IMF vector component transverse with respect to the velocity (16 ± 3%), and the solar wind plasma velocity (9 ± 1%, 37 ± 4 km/s). The modulus of the IMF vector radial component increased by 9.0 ± 2.5% during this period.