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

V B Ovodenko,D D Rogov,A A Chernyshov,B J Anderson,D S Kotova,I V Tyutin,I E Zakharenkova,M V Klimenko,P A Budnikov,J C Coxon,K G Ratovsky,D V Chugunin,A V Oinats,A V Nikolaev

doi:10.1029/2019sw002378

Abstract

AbstractWe 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.

Highlights

In the high‐latitude ionosphere, intense ionospheric irregularities and plasma structures with characteristic scales from small to large scale (>10 km) can be formed during magnetospheric storms and substorms due to two‐stream (Farley‐Buneman) (Buneman, 1963; Farley, 1963) and gradient‐drift plasma instabilities (e.g., Rogister & D'Angelo, 1970)
We present a multi‐instrumental study of ionospheric irregularities of different scales observed over the Central and East Siberia, Russia, during a moderate‐to‐strong geomagnetic storm on 27–28 May 2017
We revealed that Region 1 (R1)/Region 2 (R2) field‐aligned currents (FACs) system influences to irregularities formation and variability: (1) Increase and equatorward displacement of R1/R2 FACs leads to appearance and equatorward expansion of ionospheric irregularities; (2) degradation of R1 and R2 FACs during near noon FAC system reversal leads to disappearance of ionospheric irregularities; and (3) during downward R1 FAC and upward R2 FAC, the eastward and upward drift of ionospheric irregularities occurred

Summary

Introduction

In the high‐latitude ionosphere, intense ionospheric irregularities and plasma structures with characteristic scales from small (centimeter level) to large scale (>10 km) can be formed during magnetospheric storms and substorms due to two‐stream (Farley‐Buneman) (Buneman, 1963; Farley, 1963) and gradient‐drift plasma instabilities (e.g., Rogister & D'Angelo, 1970). 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 (Fejer & Kelley, 1980; Leadabrand et al, 1967; Schlegel, 1996) and by incoherent radars (Foster & Tetenbaum, 1991; Uspensky et al, 2011). Previous studies of radar auroral backscatter allow to list the main characteristic of these phenomena (see reviews of Cole, 1963; Fejer & Kelley, 1980; Hanuise, 1983; Haldoupis, 1989; Greenwald, 1996; Hysell, 2015). We note that radar observations can provide an approximate upper bound on the irregularity thickness in the range from

Results

Discussion

Conclusion