Sub-Auroral and Mid-Latitude GNSS ROTI Performance during Solar Cycle 24 Geomagnetic Disturbed Periods: Towards Storm’s Early Sensing

Abstract

Geomagnetic storms—triggered by the interaction between Earth’s magnetosphere and interplanetary magnetic field, driven by solar activity—are important for many Earth-bound aspects of life. Serious events may impact the electroenergetic infrastructure, but even weaker storms generate noticeable irregularities in the density of ionospheric plasma. Ionosphere electron density gradients interact with electromagnetic radiation in the radiofrequency domain, affecting sub- and trans-ionospheric transmissions. The main objective of the manuscript is to find key features of the storm-induced plasma density behaviour irregularities in regard to the event’s magnitude and general geomagnetic conditions. We also aim to set the foundations for the mid-latitude ionospheric plasma density now-casting irregularities. In the manuscript, we calculate the GPS+GLONASS-derived rate of TEC (total electron content) index (ROTI) for the meridional sector of 10–20∘ E, covering the latitudes between 40 and 70∘ N. Such an approach reveals equatorward spread of the auroral TEC irregularities reaching down to mid-latitudes. We have assessed the ROTI performance for 57 moderate-to-severe storms that occurred during solar cycle 24 and analyzed their behaviors in regard to the geomagnetic conditions (described by Kp, Dst, AE, Sym-H and PC indices).

Effects of the 12 May 2021 Geomagnetic Storm on Georeferencing Precision

“…From Figure 3, we can see that the VTEC is perturbed around the globe, including the southern part of America during the main phase of the May 2021 geomagnetic storm. On the other hand, in Figure 4h, we can see an increment in ROTI, that starts at the polar regions, propagating later the increment toward the equator, agreeing with previous studies [77,78] (see Figure 5). In Figure 7, it is possible to see the VTEC and DVTEC perturbations of the GNSS stations over Madrid, Spain and Santiago, Chile (Vizcacha station) for the May 2021 storm.…”

“…We also calculated the ROT index for the May 2021 storm period. Five stations localized in high latitudes had values of maximum ROTI peak between 3.4 and 3.9 TECu/min, and average ROTI peak ∼1.1 TECu/min, and these values are similar to those presented by Kotulak et al [77] for moderate geomagnetic storms.…”

Ionospheric Behavior during the 10 June 2021 Annular Solar Eclipse and Its Impact on GNSS Precise Point Positioning

“…On the other hand, as a consequence of the geomagnetic activity (AE-index > 500 nT) in the polar regions from 5-15 UT on DoY 162; we can see an increase in ROTI activity (ROTI 0.25 TECu/min) that starts at the northern polar region, propagating later the increment toward the equator (∼50 • N), which agrees with previous studies [29,58,59] (see Figure 6 (left panels)). In South America, the percentage of stations with ROTI activity increased from ∼12% to 24% (see Figure 6 (left panels), Figure 7 (upper panels), and Supplementary Materials, Table S4).…”