AsianScientist (Jun. 30, 2016) – Delving into the past, a Japanese team has digitalized 72 years’ worth of magnetogram recordings, taken before direct observations by satellites became available.
The analog recordings, dating back to the early 20th century, provide a window into space weather in the mid-1900’s and shed light onto future patterns of plasma movement in near-Earth space. The team published their findings in the Journal of Geophysical Research – Space Physics.
Space plasma refers to gases that are so hot that some or all of their atoms are split up into electrons and ions which can move independently of each other. It is considered the fourth state of matter, and is found throughout space. Like weather on Earth, plasma behaves dynamically.
“Direct and regular observation of plasma by satellites started after the late 1960s—almost a decade after the first man-made satellite, Sputnik 1, was launched in 1957,” explained Masahito Nosé, an author of the study and a researcher at the Kakioka Magnetic Observatory. “We needed to find an indirect parameter to infer what the plasma environment was like before satellites came along.”
Before digital observations began, analog magnetograms recorded changes in the Earth’s geomagnetic field onto photographic paper. In Japan, the first of such recordings were carried out at the Kakioka Magnetic Observatory from 1924 and continued on till 1995, even throughout World War II.
According to Nosé, analog recordings can only provide data in one-hour increments. But by digitalizing the recordings, it would be possible to get data about geomagnetic field oscillation in 7.5-second increments.
Nosé and colleagues thus scanned the paper recordings and translated the magnetogram plots into digital data. Based on this ‘new’ data, Nosé and colleagues found that although hydrogen ion levels in the plasma peaked around 1964 and 1975, the mixture included 7-10 percent oxygen ions around 1958 and 1970, making the overall plasma mass more than twice as heavy.
“There is a Japanese saying, onko chishin, that means ‘learn new things by reexamining the past.’ We’re pleased that we were able to breathe new life into the efforts of the scientists who came before us,” Nosé mused.
The article can be found at: Yamamoto et al. (2016) Estimation of Magnetospheric Plasma Ion Composition for 1956–1975 by Using High Time Resolution Geomagnetic Field Data Created from Analog Magnetograms.
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Source: Kyoto University; Photo: Shutterstock.
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