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\begin{document}

\title{Estimation of Geomagnetically Induced Currents at Low Latitude and
Equatorial Regions of Brazil During Two Great Magnetic Storms of 2015}



\author[1]{Karen Espinosa Sarmiento}%
\author[1]{Antonio Padilha}%
\author[1]{Livia Alves}%
\affil[1]{INPE National Institute for Space Research}%


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  \date{May 23, 2024}


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\begin{abstract}
The South American longitudinal sector presents the unique feature of
the presence of daytime equatorial electrojet currents (EEJ) and the
South Atlantic Magnetic Anomaly (SAMA), where the global minimum
intensity of the geomagnetic field is observed. Enhanced amplitudes are
observed in the horizontal magnetic components recorded on the ground
within the areas of influence of both the EEJ and the SAMA and therefore
it is expected that significant enhancements of GIC magnitude also occur
in these regions. We use here geomagnetic field variations data recorded
by fluxgate magnetometers from the Brazilian space weather program
(EMBRACE) to evaluate GIC effects during two strong geomagnetic storms
in March (Dst = -222nT) and June (Dst = -204nT) 2015. Among the
available geomagnetic stations, we selected those with information about
the underground electrical conductivity structure and that can be
approximated by 1-D models for calculation of the geoelectric field. GIC
levels are estimated using a realistic local power grid model located in
the central region of Brazil, artificially moved to the sites where the
geomagnetic measurements are available. Maximum GIC amplitude of about 8
A was estimated at an equatorial station positioned over high
resistivity underground, associated with the arrival of an
interplanetary pressure pulse just behind two other pulses during the
June storm. The results are also interpreted in terms of the ionospheric
currents over the measurement sites and the conductivity distribution
beneath these sites. It is observed that both EEJ and SAMA increase the
GIC amplitudes, with the greatest effects associated with EEJ. In
relation to the underlying conductivity structure, the higher GIC
effects are associated with low conductance at crustal depths, with
upper mantle depths showing minor effect.%
\end{abstract}%



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