The Anomaly of Geomagnetic Variation in Japan (Part 3)
Kuboki, T. & Oshima, H.
Abstract
The relation between the three components (⊿H, ⊿D and ⊿Z) of the vector expressing the magnetic rapid change is approximately expressed by the following formula,
⊿Z=A⊿H+B⊿D,
where H, D and Z indicate northerly horizontal intensity, easterly declination and downward vertical intensity, respectively, being measured by gammer unit.
In this paper, the authors study in detail the change of durations of phenomena and the standard deviations of the coefficients A and B in the above formula at the five permanent observatories, Memambetsu, Kakioka, Kanozan, Simosato and Kanoya, in Japan. It is found that the A and B vary considerably with the change of duration of the variation concerned, and their standard deviations become also greater as the periods of the rapid changes become shorter. The greatest standard deviation appears at the B of Simosato, as the duration of the rapid change is 2～3 minutes, and its value is 土0.9. The smallest standard deviation appears at the A of Kanoya and the B of Memambetsu, and it is 土0.04.
The ⊿Z/⊿D of Memambetsu and ⊿Z/⊿H of Kakioka, Simosato and Kanoya show diurnal changes. Amplitudes of these diurnal changes are 0.10-0.27. They are too large to be neglected in delicate studies. It is interpreted that these diurnal changes are not substantial but apparent results which are derived from the diurnal changes of ⊿D/⊿H(or ⊿H/⊿D) and “duration" of the rapid change.
In ssc and si, the more north the observatory lies, the smaller the “duration" for ⊿H of ssc (or si) becomes and the larger the diurnal change of the “duration" becomes. The “duration" and its diurnal changes for ⊿D of ssc (or si) are smaller than those of ⊿H. Also it is found that the secular change of the “duration " for ⊿H of ssc (or si) have a reverse correlation with the Wolf's relative sun-spot number.Accordingly, the diurnal change of ⊿Z/⊿H in ssc (or si) is affected by the solar activity.
At the Kanozan observatory, which is situated at a distance of 100 km to the south of Kakioka, the “Parkinson vector" and the coefficient A and B are similar to those of Kakioka. But the phase of ⊿Z is very delayed against that of ⊿H, while this event is not found at Kakioka and Kanoya. At Simosato the phase of ⊿Z is fast on the other hand.
In phenomena having sharp beginning at Kanozan, the beginning times of Z's are delayed 0.3～2 minutes against those of H's. This delay is about 1.5 minutes in ssc's. The longer the “duration" becomes, the larger this delay becomes. The cause of this event is not evident now at all, but this is a very interesting problem.
The vector S defined by the authors is made comparison with the “Parkinson vector", and the utility of S is discussed.
