Research Article

Analysis of geomagnetically induced currents at a low-latitude region over the solar cycles 23 and 24: comparison between measurements and calculations

¹ Observatório Nacional – ON/MCTI, Rua General José Cristino 77, São Cristóvão, Rio de Janeiro, RJ, Brazil
² Instituto Nacional de Pesquisas Espaciais – INPE, Av. dos Astronautas 1758, Jd Granja, São José dos Campos, Brazil
³ Universidad de la República, Facultad de Ciencias (UDELAR), Igua 4225, 11400 Montevideo, Uruguay
⁴ Universidade do Estado do Rio de Janeiro, IF, Rua S. Francisco Xavier 524, Rio de Janeiro, RJ, Brazil
⁵ Finnish Meteorological Institute, Erik Palmenin Aukio 1, 00560 Helsinki, Finland
⁶ Natural Resources Canada, Geomagnetic Laboratory, 2617 Anderson Road, Ottawa, ON K1A 0E7, Canada

^* Corresponding author: cleitonferr@hotmail.com

Received: 13 July 2015
Accepted: 29 October 2015

Abstract

Geomagnetically Induced Currents (GIC) are a space weather effect, which affects ground-based technological structures at all latitudes on the Earth’s surface. GIC occurrence and amplitudes have been monitored in power grids located at high and middle latitudes since 1970s and 1980s, respectively. This monitoring provides information about the GIC intensity and the frequency of occurrence during geomagnetic storms. In this paper, we investigate GIC occurrence in a power network at low latitudes (in the central Brazilian region) during the solar cycles 23 and 24. Calculated and measured GIC data are compared for the most intense geomagnetic storms (i.e. −50 < Dst < −50 nT) of the solar cycle 24. The results obtained from this comparison show a good agreement. The success of the model employed for the calculation of GIC leads to the possibility of determining GIC for events during the solar cycle 23 as well. Calculated GIC in one transformer reached ca. 30 A during the “Halloween storm” in 2003 whilst most frequent intensities lie below 10 A. The normalized inverse cumulative frequency for GIC data was calculated for the solar cycle 23 in order to perform a statistical analysis. It was found that a q-exponential Tsallis distribution fits the calculated GIC frequency distribution for more than 99% of the data. This analysis provides an overview of the long-term GIC monitoring at low latitudes and suggests new insight into critical phenomena involved in the GIC generation.