Preprints
https://doi.org/10.5194/hgss-2024-6
https://doi.org/10.5194/hgss-2024-6
07 May 2024
 | 07 May 2024
Status: this preprint is currently under review for the journal HGSS.

Historical evolution of the geomagnetic declination at the Royal Observatory of Madrid

Jose Manuel Tordesillas, F. Javier Pavón-Carrasco, Alberto Nuñez, and Ana Belén Anquela

Abstract. The agonic line, representing geomagnetic declinations of 0°, recently crossed the Royal Observatory of Madrid (ROM) in December 2021, causing a shift in declination values from west to east. This event constitutes a notable milestone for this significant place, where the first geomagnetic observation series in Spain commenced around 1855. Consequently, a thorough investigation into the historical evolution of the declination has been undertaken to decipher prior occurrences of the agonic line crossing at the ROM. Despite the ROM hosted the first series of geomagnetic measurements in Spain, the present lack of geomagnetic measurements in this observatory makes necessary to extend the declination measurements to other observatories distributed throughout the Iberian Peninsula to better define the passage of the agonic line since 1855 up to the present. For periods prior to 1855, a bibliographic search for declination measurements conducted in the Iberian Peninsula has been carried out, complemented by historical data from the HISTMAG database. As a result, a time-continuous curve of geomagnetic declination is generated from 1590 to 2021 at the ROM coordinates. The declination curve reveals that the agonic line also crossed the ROM 400 years ago (around 1600) passing from west to east declination values.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Jose Manuel Tordesillas, F. Javier Pavón-Carrasco, Alberto Nuñez, and Ana Belén Anquela

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hgss-2024-6', Mioara Mandea, 23 May 2024
    • AC1: 'Reply on RC1', Jose Manuel Tordesillas, 29 May 2024
    • AC4: 'Reply on RC1', Jose Manuel Tordesillas, 19 Jun 2024
  • RC2: 'Comment on hgss-2024-6', Tohru Araki, 31 May 2024
    • AC3: 'Reply on RC2', Jose Manuel Tordesillas, 19 Jun 2024
  • EC1: 'Comment on hgss-2024-6', Kristian Schlegel, 06 Jun 2024
    • AC2: 'Reply on EC1', Jose Manuel Tordesillas, 19 Jun 2024
Jose Manuel Tordesillas, F. Javier Pavón-Carrasco, Alberto Nuñez, and Ana Belén Anquela
Jose Manuel Tordesillas, F. Javier Pavón-Carrasco, Alberto Nuñez, and Ana Belén Anquela

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Short summary
In December 2021 the agonic line crossed the Royal Observatory of Madrid on its westward drift. The previous cross of the agonic line, drifting eastward, is not accurately dated because declination measurements of that time are scarce. After collecting the data made in the Iberian Peninsula over the last 500 years and reducing them to the ROM coordinates, a geomagnetic declination curve has been generated. As a result, the previous cross of the agonic line has been dated around the year 1652.