In this work, we present the uncertainties of the empirical model developed to predict the solar quiet regular daily field variation (Sq) over the Brazilian sector called the Solar Quiet Reference Field (SQRF) model. The SQRF is based on the magnetic station records from the Embrace Magnetometer Network (Embrace MagNet) during the solar cycle 24. Although the prediction and the magnetic field records have a good agreement, we observe that each magnetic station shows a random error behavior, propagating small errors in the model. Also, some physical aspects, as tidal winds and ionospheric conductivity, may have influenced our predictions. Thus, these uncertainties in the Sq field can propagate errors and influence geomagnetic indices' calculation by erroneously scaling the geomagnetic disturbances. In this context, we introduce a new approach to derive a ‘real-time’ geomagnetic index based on the SQRF model for the Sq-H field over the South American sector. We analyze one geomagnetic storm event to show that the results have a good representation of the geomagnetic indices. Finally, this analysis yields a new approach to derive the geomagnetic index for space weather applications and studies that requires an Sq field prediction.

在这项工作中，我们介绍了用来预测巴西部门太阳安静的每日日场变化（Sq）的经验模型的不确定性，称为太阳安静参考场（SQRF）模型。SQRF基于太阳周期24期间Embrace磁强计网络（Embrace MagNet）的磁站记录。尽管预测和磁场记录具有良好的一致性，但我们观察到每个磁站都表现出随机误差行为，传播模型中的小错误。此外，某些物理方面（如潮汐风和电离层电导率）可能会影响我们的预测。因此，Sq场中的这些不确定性会错误地缩放地磁干扰，从而传播误差并影响地磁指数的计算。在这种情况下，我们针对南美地区Sq-H场引入了一种基于SQRF模型的“实时”地磁指数的新方法。我们分析了一个地磁暴事件，以表明结果具有良好的地磁指数表示。最终，这种分析产生了一种新的方法来推导空间天气应用和需要Sq场预测的研究的地磁指数。