Abstract
In the present work, we evaluate the accuracy of the Solar Quiet Reference Field (SQRF) model for estimating and predicting the geomagnetic solar quiet (Sq) daily field variation in the South America Magnetic Anomaly (SAMA) region. This model is based on the data set of fluxgate magnetometers from 12 magnetic stations of the Embrace Magnetometer Network (Embrace MagNet) from 2010 to 2018. The model predicts the monthly average horizontal field of the geomagnetic quiet (Sq-H) daily variation solving a set of equations for the specified geographic coordinates in terms of the solar cycle activity, the day of the year, and the universal time. We carried out two comparisons between the prediction and observational data of the Sq-H field. The first part attempts to evaluate the accuracy for estimating the Sq-H field over Medianeira (MED, 25.30° S, 54.11° W, dip angle: − 33.45°) by using linear interpolation on the SQRF coefficients and comparing it with the data collected from April to December in 2018. None of the datasets collected at MED is part of the dataset used to build the SQRF model. The second part of the analysis attempts to evaluate the accuracy for predicting the quiet daily field variation over Cachoeira Paulista (CXP, 22.70° S, 45.01° W, dip angle: − 38.48°). The dataset collected at CXP before the period analyzed in the present work is part of the dataset used to build the SQRF model. Thus, the prediction accuracy is tested using magnetic data outside the time interval considered in the model. The prediction results for both locations show that this empirical model’s outputs present a good agreement with the Sq-H field obtained from the ground-based magnetometer measurements. The accuracy of the SQRF model (high correlation, r > 0.9) indicates a high potential for estimating and predicting geomagnetic quiet daily field variation. Concerning space weather applications, the model improves the scientific insight and capability of space weather prediction centers to predict the variability of the regular solar quiet field variation as reference conditions, which may include areas with no measurements.
Highlights
Over the past centuries, the International Polar Years (IPY, 1882–1883 and 1932–1933) and the International Geophysical Year (IGY, 1957–1958) encouraged the studies and monitoring of the Earth’s magnetic field (Jankowski and Sucksdorff 1996)
The Solar Quiet Reference Field (SQRF) model is based on Yamazaki et al (2011), in which the geomagnetic field daily variation is calculated through the least-square fitting of multivariable functions to observational data
The SQRF computed the values for Cuiabá (CBA, 15.55° S, 56.07° W, dip angle: − 18.58°) and São Martinho da Serra (SMS, 29.44° S, 53.82° W, dip angle: − 37.69°) to obtain the modeled results for Medianeira (MED, 25.30° S, 54.11° W, dip angle: − 33.45°), a region close to the South America Magnetic Anomaly (SAMA) center
Summary
The International Polar Years (IPY, 1882–1883 and 1932–1933) and the International Geophysical Year (IGY, 1957–1958) encouraged the studies and monitoring of the Earth’s magnetic field (Jankowski and Sucksdorff 1996). We attempt to develop an estimating and predicting tool for obtaining the solar quiet daily variation of the geomagnetic field at the SAMA.
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