Abstract
Abstract. The historical magnetic observatory Clementinum operated in Prague from 1839 to 1926. The data from the yearbooks that recorded the observations at Clementinum have recently been digitized and were subsequently converted, in this work, into the physical units of the International System of Units (SI). Introducing a database of geomagnetic data from this historical source is a part of our paper. Some controversial data are also analysed here. In the original historical sources, we identified an error in using the physical units. It was probably introduced by the observers determining the temperature coefficient of the bifilar apparatus. By recalculating the values in the records, some missing values are added; for instance, the temperature coefficients for the bifilar magnetometer, the baselines, and the annual averages for the horizontal intensity in the first years of observations were redetermined. The values of absolute measurements of the declination in 1852, which could not be found in the original sources, were also estimated. The main contribution of this article rests in critically reviewed information about the magnetic observations in Prague, which is, so far, more complete than any other. The work also contributes to the space weather topic by revealing a record of the now almost forgotten magnetic disturbance of 3 September 1839.
Highlights
Reliable long time series of geomagnetic records are needed for studying the long-term behaviour of the Earth’s magnetic field, for instance its secular variation (Cafarella et al, 1992)
The magnetic data published in the yearbooks Magnetische und Meteorologische Beobachtungen zu Prag include absolute observations, regular variation observations, more frequent observations during magnetically disturbed conditions, and simultaneous observations on term days agreed in the frame of the Göttingen Magnetic Union (GMU)
The presented study can be primarily conceived as a presentation of the unique database collected from geomagnetic recording at the Clementinum observatory in Prague during the 19th century
Summary
Reliable long time series of geomagnetic records are needed for studying the long-term behaviour of the Earth’s magnetic field, for instance its secular variation (Cafarella et al, 1992). This work presents the first comprehensive review of the historical magnetic data recorded at the Clementinum observatory in Prague. In 1833, Gauss and Weber finished the construction of the magnetic observatory in Göttingen and developed or improved instruments to measure the magnetic field, such as the unifilar and bifilar magnetometers. Gauss and Weber joined the activity of Alexander von Humboldt in establishing a worldwide network of observatories, known as the Göttingen Magnetic Union (GMU), that made simultaneous measurements at specific intervals (called term days). It was important that from the very beginning all measurements were published in the yearbooks called Magnetische und meteorologische Beobachtungen zu Prag (Magnetic and meteorological observations in Prague). Searching for geomagnetic disturbances in the past, and their analysis, is important for understanding the causes of extreme geomagnetic activity At present, this kind of research can be beneficial for setting up reliable space weather forecast models.
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