Datasets of the solar quiet (Sq) and solar disturbed (SD) variations of the geomagnetic field at a midlatitudinal station in Europe obtained by different methods

Published: 02-03-2021| Version 1 | DOI: 10.17632/jcmdrm5f5x.1
Anna Morozova,


Here we present datasets of daily variation obtained from the geomagnetic field's raw observations recorded at the Coimbra Magnetic Observatory (COI, Portugal) between 01.01.2007 and 31.12.2017, covering almost the entire solar cycle 24. Two methods were used to extract daily variability from the raw geomagnetic hourly data. The first method uses the so-called “geomagnetically quiet days” to calculate S-type variations as daily means resulting in the data sub-set named “IQD Sq and SD”. The second method uses the principal component analysis (PCA) to decompose the original series into main variability modes. The first three modes produced by PCA and explaining up to 98% or the variability of the raw data are in the data sub-set named “PCA modes”. Both methods allow to extract regular geomagnetic field variations related to daily variations (S-type variations) in the ionospheric dynamo region and some magnetospheric currents (e.g., field aligned currents). The location of COI in middle latitudes near the latitude of the ionospheric Sq current vortex's focus allows studying its seasonal and decadal variability using the S-type regular variations of the geomagnetic field measured near the ground. The S-type variations for the X and Y components of the geomagnetic field obtained at the COI observatory can also be re-scaled and used to analyze geomagnetic field variations obtained at other European geomagnetic observatories at close latitudes. The S-type variations for the Z component of the geomagnetic field obtained at the COI observatory can be compared to similar variations observed at more continental regions to study the so-called “coastal effect” in the geomagnetic field variations. Institution: University of Coimbra, Geophysical and Astronomical Observatory, Coimbra Magnetic Observatory City: Coimbra Country: Portugal Latitude and longitude for collected data: 40º 13’ N, 8º 25.3’ W, 99 m a.s.l. Primary data sources: The raw geomagnetic field data can be downloaded from the World Data Centre for Geomagnetism, Geomagnetism Data Portal (, station name: “Coimbra”, IAGA code: “COI”


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The data were produced from the raw observations data using two different approaches: 1. using 5 international quiet days (IQD) provided by the GeoForschungsZentrum (GFZ) Potsdam 2. using the principal component decomposition (PCA) The raw data of the geomagnetic field variations (1h cadence) from 01.01.2007 to 31.12.2017 were divided into monthly blocks. Each monthly block was analyzed separately. Two types of Sq variations were calculated: 1. SqIQD and SDIQD calculated using the IQD for each of the 12*11 months; 2. PCA modes (1st, 2nd and 3rd modes)