# Effects of the 12 May 2021 Geomagnetic Storm on Georeferencing Precision
## 1 Introduction  
The tendency to incorporate autonomous or tele-operated systems in certain industries around the globe requires careful analysis over the performance of the technology that supports this activity. One of the key elements in those systems is the global navigation satellite system (GNSS), which allows the geolocation of a receiver almost anywhere in the world. However, GNSS as a radio-link-based system can be perturbed by variations in the ionosphere. In particular in Chile, mining, fishing, and agriculture activities are relevant economic sectors in Chile that are exploring the migration to a more tele-operated/autonomous operation. Due to this requirement, it is imperative to study the robustness of the GNSS systems along the country, in particular when geomagnetic storms are produced. One of the most important drivers of ionospheric variations at a global scale is solar activity. During a geomagnetic storm, the ionosphere can be greatly perturbed through the Sun-solar wind-magnetosphere-ionosphere-atmosphere coupling process. Perturbations in the ionosphere, in particular electrons, can produce disturbances in space-based technology and their products such as communication disruptions and imprecision in the positioning estimation of global navigation satellite system (GNSS). The enhancement or oscillations in the ionospheric electron content influence the signal between asatellite (GNSS/communication) and a receiver. In particular, the signal delay is affected differently depending on the signal frequency, resulting in a reduction in the accuracy of multifrequency GNSS receivers. A geomagnetic storm is a major temporary disturbance in the Earth's magnetic activity and is associated with solar activity, e.g., coronal mass ejection (CME) and high-speed solar wind stream (HSS) [1]. When there is greater solar activity, geomagnetic storms are mainly generated by CME, while during moments of less solar activity, it is the coronal holes that have a dominant effect [2]. Geomagnetic storms occur when there is a large sudden change in the solar wind dynamic pressure at the magnetopause [3]. The distinctive characteristic of a geomagnetic storm is a clear decrease in the horizontal intensity of the magnetic field [3]. Geomagnetic storms can be usually divided into three main phases: initial, main, and recovery [4; 5; 6]. The geomagnetic storms are detected prior to the ionospheric disturbances and to the decrease in positioning estimation. Different geomagnetic indices are used to characterize geomagnetic storms such as the disturbance storm time (Dst) index, geomagnetic disturbance (Kp), averaged geomagnetic activity (Ap) (based on data from a set of specific Kp stations), and the auroral electrojet (AE) index, where the Dst-index is associated with the effects on the equatorial region, the Kp-index to the midlatitudes, and the AE-index at high latitudes since it characterizes the intensity of ionospheric currents during magnetic storms and substorms activity [7; 8]. The Dst-index has been used historically to characterize the severity of a geomagnetic storm. Depending on the Dst value, the storms are usually classified in ranges such as weak (\(-30\) nT and \(-50\) nT), moderate (\(-50\) nT and \(-100\) nT), intense (\(-100\) nT and \(-200\) nT), very intense (\(-200\) nT and \(-350\) nT), and great (Dst below \(-350\) nT) [3; 4; 9; 10]. Furthermore, the Kp-index is based on 3 h measurements from ground-based magnetometers around the world ([[https://www.spaceweatherlive.com/](https://www.spaceweatherlive.com/)]([https://www.spaceweatherlive.com/](https://www.spaceweatherlive.com/)), accessed on 3 December 2021).