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The evolution of the Earth's magnetic field is the consequence of
the dynamics of the Earth's internal field, and its interaction with
the solar wind forcing. Spatial and temporal fluctuations at various
scales develop as a consequence of this nonlinear coupling, providing
information to study the Earth's inner dynamics, the Sun's
activity,  and their interaction.

In this work, we propose to approach this problems by means of
complex networks, and the study of community structures between them.
By using records by 59 magnetometeres during the 23rd solar cycle,
located on the Earth's surface, [1] we define a complex network where
nodes are the magnetometers, and connections represent correlations
between their readings. The resulting network thus contains
spatial and temporal information of the Earth's magnetic field.

Then,we apply community detection algorithms to determine closely
correlated sets of nodes within the network. We investigate whether
the evolution of the community structure carries information about the
change in magnetic field topology associated to variations in the
Sun's magnetic activity along the solar cycle.

Our work suggests that analysis of the Earth’s magnetic field
variations using complex network and community structure analyses, can
be useful to understand the geomagnetic activity along the solar
cycle [2, 3, 4].

This project has been financially funded by FONDECyT, grant number
1242013 (VM).

[1] World Data Center for Geomagnetism, Kyoto,
http://wdc.kugi.kyoto-u.ac.jp/dstdir/dst2/onDstindex.html.
[2] L. Orr, S. C. Chapman, J. W. Gjerloev, and W. Guo, Network community structure of substorms using SuperMAG magnetometers, Nuovo Cim. 12, 1842, 2021.
[3] S. Lu, H. Zhang, X. Li, Y. Li, C. Niu, X. Yang, and D. Liu, Complex network description of the ionosphere, Nonlinear Proc. Geophys. 25, 233-240, 2018.
[4] A. Najafi, A. H. Darooneh, A. Gheibi, and N. Farhang, Solar flare modified complex network, Astrophys. J. 894, 66, 2020.