Dynamic Response of Ionospheric Plasma Density to the Geomagnetic Storm of 22‐23 June 2015

Abstract

On 21–22 June 2015, three consecutive interplanetary shocks slammed into the Earth's magnetosphere. Immediately after the third shock at 18:36 UT on 22 June, marked by an exceptional sudden storm commencement with an amplitude of ΔSYM‐H = ∼106 nT, a major geomagnetic storm commenced. In the present study, a multi‐instrument approach comprising observations, data analysis, and modeling is used to examine the global ionospheric response. Results show that enhanced storm time processes produced major total electron content (TEC) variations at different latitudes, longitudes, and phases of the storm. A closer inspection of the TEC observations reveals strong longitudinal and hemispherical asymmetry. In addition, multiple equatorward and poleward propagating traveling ionospheric disturbances (TIDs) were detected in the TEC data. Equatorward propagating TIDs are consistent with vertical neutral winds simulated from Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model; however, poleward TIDs were not reproduced in the model. We find that a combination of driving processes including enhanced high‐latitude injection, prompt penetration electric fields, disturbance dynamo effect, neutral winds, and composition changes were acting at different stages of the storm.

Ionospheric Response at Conjugate Locations During the 7–8 September 2017 Geomagnetic Storm Over the Europe‐African Longitude Sector

“…The TID activity is more pronounced in the Southern than in the Northern Hemisphere especially on the 8 September 2017. Large‐scale TIDs are known to contribute to positive storm effects (e.g., Prölss, 1993a), and their observations during periods of geomagnetic storms in relation to enhanced ionospheric electron density and/or TEC have been widely reported (e.g., Borries et al, 2016; Ding et al, 2007; Ngwira et al, 2019; Zakharenkova et al, 2016, and references therein).…”

“…Thus, there are varying physical mechanisms used to explain different observations (e.g., Buonsanto, 1999; Prölss, 1993a; 1993b). It is now accepted that the composition changes within the thermosphere are largely responsible for negative storm effects (e.g., Buonsanto, 1999; Danilov, 2001; Prölss, 1993a), while the interpretation of positive storm effects involves various mechanisms such as increased or enhanced vertical E × B drift, occurrence of atmospheric gravity waves, and prompt penetrating electric fields (e.g., Ding et al, 2007; Ngwira et al, 2019; Prölss, 1993a; Tsurutani et al, 2004; Vijaya Lekshmi et al, 2011, and references therein). Inevitably, similar latitude regions in different hemispheres could present different responses due to the physical mechanisms that may be dominant in each hemisphere.…”

Geomagnetic Pulsations Driving Geomagnetically Induced Currents

“…During the time between the two substorms that high-amplitude oscillations with period of around 23 min are observed in the B field across eastern North America and in the PAR GIC data shown here. Particle precipitation and currents associated with these substorms resulted in a strong westward electrojet (seen in the SML 10.1029/2020SW002557 index Newell & Gjerloev, 2011), FACs of around 6-7 MA (Nakamura et al, 2016) and equatorward traveling ionospheric disturbances (Ngwira et al, 2019). As the storm was reaching its peak, the equatorward edge of the auroral oval as estimated by the SSUSI measurements (Paxton et al, 1992(Paxton et al, , 1993(Paxton et al, , 2017 was around 53°g eomagnetic latitude and centered around the longitudinal region of interest (see Figure 4).…”

Understanding Inter-Hemispheric Traveling Ionospheric Disturbances and Their Mechanisms

“…The experimental GNSS-TEC technique is employed in this study due to its relatively wide spatial coverage as compared to other instruments. Data from observational system and theoretical studies have been used both separately and jointly to investigate the sources and mechanisms responsible for TIDs e.g., [1,3,6,7,11,[17][18][19][20].…”