Resolution No.3 (1975): Publication of aa indices in IAGA Bulletin 32

IAGA, considering that the three-hourly indices "aa" constitute a homogeneous series for quantitative estimation of geomagnetic activity beginning with the year 1868, recommends the yearly publication of the "aa" indices in place of the Ci-indices in the IAGA Bulletin 32 beginning with the data for the year 1975.