ALBERT

Description: The Japan Meteorological Agency has been conducting long-term magnetic observations at Kakioka (1913-), Memambetsu (1952-) and Kanoya (1958-), and archived the observations in magnetograms. We have already converted these magnetograms into digital images at 600 dpi for the periods 1924-1983 (Kakioka), 1963-1984 (Memambetsu) and 1964-1984 (Kanoya). In 1956, time marks in the magnetograms were changed from 'gap' to 'vertical lines'. For the period after 1956, we have been producing 1-minute and 7.5-second digital values by our self-developed automated tracing software. The digitization was finished for the periods 1956-1983 (Kakioka) and 1968-1984 (Memambetsu and Kanoya), except for times of some abrupt phenomena. As automatic reading by the software is not applicable to such time intervals, we keep working on them with manual reading software. Our ultimate goal is to complete digitization of all records prior to 1956, which involve a number of extreme events (PC, SFE, SC) including the 24 March 1940 event, the greatest SC event since 1868. 7.5-second data would be very useful resources for elucidating the Sun-Earth coupling processes. However, sharp peaks associated with SCs may not be adequately resolved even with those data. Additional information is desirably obtained by spotting apexes of individual peaks. Challenges to be addressed include: (1) difficulty in strict time identification due to the time mark gap, (2) difficulty in tracing lines due to dimness of the magnetograms, and (3) inaccuracy of the time axis due to paper distortion. New working tools and a certain amount of labor will be further required.