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Monitoring of Time Changes of Conductivity Anomaly Transfer Functions at Japanese Magnetic Observatory Network
The conductivity anomaly (CA) transfer functions at Japanese magnetic observatory network (Memambetsu, Kakioka, Matsuzaki, Omaezaki and kanoya) are calculated day by day in order to examine their time changes. The power spectral method is employed to calculate the transfer functions with periods of 120. 60. 30 and 10 minutes by utilizing all (1440) geomagnetic one-minute values in one day. Defining the error factor which indicates how adequate the Z variation is reproduced from linear combination of the H and D variations. We select adequate values of the transfer functions for their monthly means. As a result, the secular change of the 10.minute.period Au's for Kakioka (-0.05/30years) is essentially consistent with its secular change for 1940-1970 obtained by Yanagihara and Nagano(I976). The 10-minute-period Au's for Kanoya and for Memambetsu increase in contrast to that for Kakioka. Those for Matsuzaki and for Omaezaki have decreasing Au's with annual change rates of about 0.02, although it is uncertain to conclude that these secular changes are natural because of contamination by noises.
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