Spatial and Temporal Evolution of Different‐Scale Ionospheric Irregularities in Central and East Siberia During the 27–28 May 2017 Geomagnetic Storm

Abstract

We present a multi-instrumental study of ionospheric irregularities of different scales (from tens of centimeters to few kilometers) observed over the Central and East Siberia, Russia, during a moderate-to-strong geomagnetic storm on 27-28 May 2017. From high-frequency (HF) and ultrahigh-frequency (UHF) radar data, we observed an intense auroral backscatter developed right after the initial phase of the geomagnetic storm. Additionally, we examined variations of Global Positioning System (GPS)-based ROT (rate of TEC changes, where TEC is total electron content) for available GPS receivers in the region. Ionosondes, HF, and UHF radar data exhibited a presence of intense multi-scale ionospheric irregularities. We revealed a correlation between different-scale Auroral/Farley-Buneman ionospheric irregularities of the E layer during the geomagnetic storm. The combined analysis showed that an area of intense irregularities is well connected and located slightly equatorward to field-aligned currents (FACs) and auroral oval at different stages of the geomagnetic storm. An increase and equatorward displacement of Region 1 (R1)/Region 2 (R2) FACs leads to appearance and equatorward expansion of ionospheric irregularities. During downward (upward) R1 FAC and upward (downward) R2 FAC, the eastward and upward (westward and downward) E × B drift of ionospheric irregularities occurred. Simultaneous disappearance of UHF/HF auroral backscatter and GPS ROT decrease occurred during a prolonged near noon reversal of R1 and R2 FAC directions that accompanied by R1/R2 FAC degradation and disappearance of high-energy auroral precipitation.A significant feature of such irregularities is that they scatter and reflect radio waves. That is, why these irregularities were well investigated by coherent radars in high-frequency (HF), very HF, ultrahigh-frequency (UHF), and L bands (

Auroral Ionosphere Model with PC Index as an Input

“…Based on these results, it becomes possible to use PC index instead of Newell's function in the OVATION-Prime precipitation model. The modified OVATION-Prime with PC application was already successfully used to study processes in the Earth's atmosphere in [34], where the multi-regression formula was taken to switch from N to PC index:…”

Extreme Birkeland Currents Are More Likely During Geomagnetic Storms on the Dayside of the Earth

“…During geomagnetic storms, the enhanced ring current retards the onset of nightside reconnection and thus the onset of substorms, allowing the auroral oval to reach larger sizes prior to substorm expansion phase onset (Milan, 2009; Milan, Grocott, et al., 2009; Milan, Hutchinson, et al., 2009). Recently, it has been demonstrated that storm times are vital to understanding extreme GIC signatures (Smith et al., 2019, 2021), and work has been done to explore Birkeland currents during geomagnetic storms (e.g., Kleimenova et al., 2021; Lukianova, 2020a, 2020b; Maute et al., 2021; Ovodenko et al., 2020; Pedersen et al., 2021, 2022, 2023).…”

“…During geomagnetic storms, the enhanced ring current retards the onset of nightside reconnection and thus the onset of substorms, allowing the auroral oval to reach larger sizes prior to substorm expansion phase onset (Milan, 2009;Milan, Grocott, et al, 2009;Milan, Hutchinson, et al, 2009). Recently, it has been demonstrated that storm times are vital to understanding extreme GIC signatures (Smith et al, 2019(Smith et al, , 2021, and work has been done to explore Birkeland currents during geomagnetic storms (e.g., Kleimenova et al, 2021;Lukianova, 2020aLukianova, , 2020bMaute et al, 2021;Ovodenko et al, 2020;Pedersen et al, 2021Pedersen et al, , 2022Pedersen et al, , 2023. Hutchinson et al (2011) developed a method to algorithmically identify the individual phases (initial, main, and recovery phases) of geomagnetic storms, finding that the duration of the main phase increased with storm intensity up to a point but then started to decrease again, which they argued was contrary to Yokoyama and Kamide (1997).…”

Ionospheric GPS-TEC responses from equatorial region to the EIA crest in the South American sector under intense space weather conditions

“…In this investigation, we present and discuss in detail the ionospheric impact in the South American sector produced by the intense geomagnetic storm that occurred in May 2017. The effects of this geomagnetic storm was already investigated in other sectors, such as over North America by Jonah et al (2018) that using GPS observations, reported the presence of both equatorward propagating large scale traveling ionospheric disturbances (TIDs) and poleward propagating medium scale TIDs, over Europe by Pezzopane et al (2019) that using data from the WIND spacecraft, from the GOES and THEMIS satellites, INTERMAGNET magnetometer array, and GPS receivers, investigated the effects on magnetosphere-plasmasphere-ionosphere system, over Central and East Siberia by Ovodenko et al (2020) that presented a muti-instrumental study of ionospheric irregularities of different scales from tens of centimeters to few kilometers, and over Asian sector by Liu et al (2020) that using multi-instrumental observations, including GNSS-TEC and other complementary datasets, investigated the multi-scale ionospheric responses. For the present investigation, latitudinal/longitudinal VTEC differences from selected GPS stations were used in orther to evaluate the ionospheric response to the geomagnetic storm at different chains over the South American sector.…”