Abrupt change in secular variation rate of geomagnetic north component observed in Japan, by Hiroo Mizuno - comments: Reply.

In his comment on my paper (MizuNO, 1980), Alldredge expressed a serious objection against the assumption of linear relationship between sunspot number and the influence of solar activity on the annual mean value of the north component of the earth's magnetic field. When he wrote the comment, the results from the annual mean values of 1977 and 1978 were not yet shown on Figs. 3 and 4 of the paper. It will be shown below that the conclusions on the linear relationship stated in the paper can be confirmed when the data of 1977 and 1978 which are now available are included. In Fig. 1, t from 1975.0 to 1978.0 are plotted versus S, The points for 1975 through 1978 lie within parallel straight lines d and e which have the same direction as the lines a, b, and c in Fig. 3 of the paper. We may consider that the north component is also influenced by the solar activity during this period of time with the same rate oft:5=1:5 which is derived from Eq. (1) in the paper. X for S=0 is estimated to be 12-15 nT/ year from 1975 onwards while it is -8.2 nT/year before 1974 as is described in the paper, showing a transition from a relatively stable state to another. From 1977 to 1978, sunspot number showed a very rapid rate of increase. In 1977, the annual mean value of sunspot number was 27.5 and it became 111.7 in 1978. Annual rate of increase for 1978.0 was 84.2/year. It is worth noting that