Digitization of Bromide Paper Records to Extract One-Minute Geomagnetic Data

Mashiko, Norimichi; Yamamoto, Tetsuya; Akutagawa, Mayumi; Minamoto, Yasuhiro

doi:10.2481/dsj.wds-046

Cited by 6 publications

(7 citation statements)

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“…The photographic papers may induce the uncertainties in the amplitude and timing. Regarding the amplitude, Mashiko et al [] compared differences between the digital data created from the analog magnetograms and data measured by the digital recording magnetometer for 1 min data. They found that the standard deviations of the differences over 10 min intervals (i.e., 10 data points) are ≤0.1 nT and ≤0.2 nT for 82% and 98% of intervals, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…From the analog magnetograms recorded at Kakioka, Mashiko et al [] created digital data for the period between 1956 and 1975, in which we can find geomagnetic pulsations. In their digitization method, the photographic records are scanned at a resolution of 600 pixels per inch, which is equivalent to a time resolution of approximately 7.5 s per pixel.…”

Section: Data Setsmentioning

confidence: 99%

“…The amplitude resolution is approximately 0.1 nT (for the H and Z components) and 0.01 min (for the D component) per pixel. A more detailed description of the digitization is provided in the study conducted by Mashiko et al []. Such high time resolution and high amplitude resolution enable us to identify Pi2 pulsations and examine their wave periods.…”

Section: Data Setsmentioning

confidence: 99%

“…At Kakioka Magnetic Observatory in Japan (36.2 ∘ geographic latitude, 140.2 ∘ geographic longitude, and LT = UT + 9 h), geomagnetic field observations on photographic paper started in 1924 and ended in 1995. Recently, Mashiko et al [2013] have developed software that scans the Kakioka analog magnetograms to create digital values with a time resolution of 7.5 s. This software was applied to the magnetograms for [1956][1957][1958][1959][1960][1961][1962][1963][1964][1965][1966][1967][1968][1969][1970][1971][1972][1973][1974][1975]. Thus, the obtained digital values facilitate the study of various geomagnetic phenomena in old days.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of magnetospheric plasma ion composition for 1956–1975 by using high time resolution geomagnetic field data created from analog magnetograms

Yamamoto

Nosé

Mashiko³

et al. 2016

JGR Space Physics

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This study addresses the ion composition in the magnetosphere before the satellite era. We estimate the plasma ion mass for 1956–1975 from the period of low‐latitude Pi2 pulsations found in digital geomagnetic field data that are created from analog magnetograms at Kakioka. The period of investigation covers most of solar cycle 19 and the whole solar cycle 20. To consider long‐term variation, the moving average of the estimated plasma ion mass is calculated with a 1 year time window. We find that 1 year moving average of the plasma ion mass changed by a factor of ∼2 during one solar cycle (i.e., between ∼1.1 amu and ∼2.4 amu for solar cycle 19 and between ∼1.1 amu and ∼2.0 amu for solar cycle 20). The correlation coefficient between the 1 year moving average of the plasma ion mass and that of the F10.7 index is 0.86. This result supports the idea that in long‐term variation, solar radiation increases the density and the temperature of O+ ions in the ionosphere, leads to the outflow of O+ ions, and contributes to the enhancement of the plasma ion mass in the nightside magnetosphere. The digital data created from analog magnetograms provide an important clue to know the space environment in old days and are advantageous for studies of the space weather and space climate.

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Section: Discussionmentioning

confidence: 99%

Section: Data Setsmentioning

confidence: 99%

Section: Data Setsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Estimation of magnetospheric plasma ion composition for 1956–1975 by using high time resolution geomagnetic field data created from analog magnetograms

Yamamoto

Nosé

Mashiko³

et al. 2016

JGR Space Physics

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“…1c). We recovered the data from 1969 to 1974 by digitizing the lines on the bromide papers using the method of Mashiko et al (2013), and hereafter, focus on the records in late November in 1973 (Periods I-III) spanning three bromide papers ( Fig. 1c).…”

Section: Datamentioning

confidence: 99%

Possible slow slip event beneath the Kii Peninsula, southwest Japan, inferred from historical tilt records in 1973

Kano

2019

Earth Planets Space

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Recent geodetic measurements have detected recurrent slow slip events (SSEs) in many subduction zones. Numerical simulations suggest that the recurrence intervals and magnitudes of such SSEs decrease in the later stage of the interseismic period. Therefore, activities of SSEs and their temporal variations in recurrence intervals and magnitudes provide important clues for evaluating future large earthquakes. However, our knowledge of recurrent SSEs before the establishment of dense observation networks is limited. Here, we report a possible SSE in 1973 beneath the Kii peninsula along the Nankai subduction zone, southwest Japan, where magnitude 8 class earthquakes such as the 1944 Tonankai and 1946 Nankai earthquakes repeatedly occur. The possible SSE was detected by a horizontal pendulum tiltmeter installed in 1947 at the Kishu observatory. We recovered and converted the original tilt records from 1969 to 1974 drawn on bromide (light sensitive) papers to digital tilt records. In late-November 1973, there was a slow transient signal down to the northeast of about 1.4 μrad, lasting about 1-3 days. Assuming this crustal deformation was due to an SSE, we searched for a possible fault model by adopting the already-known SSE models occurring from 1996 to 2012 as template models. Among the 42 template fault models, five models were able to qualitatively explain the direction of the observed tilt change. The centroids of these fault models were located about 30-60 km to the west of the observatory. In the source region, two magnitude 5 class earthquakes occurred before the initiation of the transient signal, and thus may be related to the occurrence of the possible SSE. In contrast, the magnitude of the calculated tilt change was about 1-2 order smaller than that of the observed tilt change. This discrepancy could be partly explained by a slip amount larger than that in the template models, which suggests that the possible SSE in 1973 was larger than those detected by recent observations. Further investigation of historical data on crustal deformation will reveal more about the temporal change in the recurrence intervals and magnitudes of SSEs during earthquake cycles of large earthquakes. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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Availability and Access to Data from Kakioka Magnetic Observatory, Japan

Minamoto

2013

Data Sci. J.

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Digitization of Bromide Paper Records to Extract One-Minute Geomagnetic Data

Cited by 6 publications

References 0 publications

Estimation of magnetospheric plasma ion composition for 1956–1975 by using high time resolution geomagnetic field data created from analog magnetograms

Estimation of magnetospheric plasma ion composition for 1956–1975 by using high time resolution geomagnetic field data created from analog magnetograms

Possible slow slip event beneath the Kii Peninsula, southwest Japan, inferred from historical tilt records in 1973

Availability and Access to Data from Kakioka Magnetic Observatory, Japan

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