Solar and lunar daily geomagnetic variations and their equivalent current systems observed by Swarm

This paper describes solar and lunar daily variations of the geomagnetic field over low- and mid-latitude regions, using vector magnetometer data from Swarm satellites at altitudes of ∼ 500 km during the solar minimum years of 2017–2020. The average solar variation of the geomagnetic field is within...

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Bibliographic Details
Published inEarth, planets, and space Vol. 74; no. 1; pp. 1 - 21
Main Author Yamazaki, Yosuke
Format Journal Article
LanguageEnglish
Published Berlin/Heidelberg Springer Berlin Heidelberg 23.06.2022
Springer
Springer Nature B.V
SpringerOpen
Subjects
2. Aeronomy
Atmosphere
Atmosphere, Upper
Daily variation
Diurnal variations
DynamicEarth: Earth’s Interior
Earth and Environmental Science
Earth Sciences
Electric fields
Equivalence
Field aligned currents
Fourier analysis
Geology
Geomagnetic field
Geomagnetic variations
Geomagnetism
Geophysics/Geodesy
Ground stations
Harmonic analysis
Ionospheric currents
Near Space Interactions
Observations
Ocean
Solar minimum
Spherical harmonics
Surface
Swarm
Vortices
Germany
Ionospheric currents
Swarm
Daily variation
L
Sq
Geomagnetic field
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Summary:This paper describes solar and lunar daily variations of the geomagnetic field over low- and mid-latitude regions, using vector magnetometer data from Swarm satellites at altitudes of ∼ 500 km during the solar minimum years of 2017–2020. The average solar variation of the geomagnetic field is within the range of ±14 nT, while the lunar variation is within ±2 nT. The latter is comparable to the ocean tidal field. A spherical harmonic analysis is performed on the solar and lunar variations to evaluate their internal and external equivalent current systems. The results show that both the solar and lunar variations are mainly of internal origin, which can be attributed to combined effects of ionospheric dynamo currents and induced underground currents. Global patterns of the internal solar and lunar current systems are consistent with the corresponding external current systems previously reported based on ground observations. The Swarm external currents are mainly in the meridional direction, and are likely associated with interhemispheric field-aligned currents. Both the internal and external current systems depend on the season and longitude. Graphical Abstract
ISSN:1880-5981
1343-8832
1880-5981
DOI:10.1186/s40623-022-01656-9