Datasets of the solar quiet (Sq) and solar disturbed (SD) variations of the geomagnetic field from the mid latitudinal Magnetic Observatory of Coimbra (Portugal) obtained by different methods

TL;DR

This paper presents datasets of daily geomagnetic field variations from Coimbra Observatory over 2007-2017, using two methods—quiet days and PCA—to extract regular variations related to solar activity, aiding geomagnetic studies.

Contribution

The paper introduces two novel datasets of geomagnetic variations derived from raw data using quiet day and PCA methods, enabling detailed analysis of solar and geomagnetic activity effects.

Findings

Datasets cover almost an entire solar cycle 24.

Both methods effectively extract daily geomagnetic variations.

Datasets can be used for comparative studies across European observatories.

Abstract

Here we present datasets of daily variation obtained from the geomagnetic field raw observations recorded at the Coimbra Magnetic Observatory (COI, Portugal) in 2007-2017, 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 per cent of 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. The COI location near the mean latitude of the ionospheric Sq current vortex focus allows studying its 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 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. The dataset described in this paper is analyzed in a companion paper Comparison of the solar variations of the geomagnetic field at the Coimbra Magnetic Observatory (COI) obtained by different methods: effect of the solar and geomagnetic activity by A. Morozova and R. Rebbah submitted to ASR.