Ground-Based GNSS and Satellite Observations of Auroral Ionospheric Irregularities during Geomagnetic Disturbances in August 2018

Abstract

The 25–26 August 2018 space weather event occurred during the solar minimum period and surprisingly became the third largest geomagnetic storm of the entire 24th solar cycle. We analyzed the ionospheric response at high latitudes of both hemispheres using multi-site ground-based GNSS observations and measurements onboard Swarm and DMSP satellites. With the storm development, the zones of intense ionospheric irregularities of auroral origin largely expanded in size and moved equatorward towards midlatitudes as far as ~55–60° magnetic latitude (MLAT) in the American, European, and Australian longitudinal sectors. The main ionospheric trough, associated with the equatorward side of the auroral oval, shifted as far equatorward as 45–50° MLAT at both hemispheres. The interhemispheric comparison revealed a high degree of similarity in a large expansion of the auroral irregularities oval towards midlatitudes, in addition to asymmetrical differences in terms of larger intensity of plasma density gradients and structures over the Southern auroral and polar cap regions. Evolution of the intense ionospheric irregularities and equatorward expansion of the auroral irregularities oval were well correlated with increases of geomagnetic activity and peaks of the auroral electrojet index.

What Is Unusual About the Third Largest Geomagnetic Storm of Solar Cycle 24?

“…has also been reported to have widespread space weather effects at Earth (Abunin et al, 2020;Zakharenkova et al, 2021) and Mars (Thampi et al, 2021). Although some authors claim that this is a stealth CME (Mishra & Srivastava, 2019;Nitta et al, 2021;Piersanti et al, 2020), the near-surface signatures are clear although weak (Abunin et al, 2020;Chen et al, 2019).…”

What is Unusual about the Third Largest Geomagnetic Storm of Solar Cycle 24?

“…These authors identify the solar source of this storm as a filament channel eruption and track the CME propagation in the corona and interplanetary medium. The event has also been reported to have widespread space weather effects at Earth (Zakharenkova et al 2021;Abunin et al 2020) and Mars (Thampi et al 2021). Although some authors claim that this is a stealth CME (Mishra and Srivastava 2019;Piersanti et al 2020;Nitta et al 2021), the near-surface signatures are clear although weak (Chen et al 2019;Abunin et al 2020).…”

Tracing ionospheric irregularities generated during geomagnetic storms using ground-based GNSS observations and LEO polar orbiting satellites

“…For the cases of strong ionospheric responses, we investigated dynamics of the storm-induced ionospheric irregularities development on a global scale using the multi-site ground-based GNSS ROTI observations. The numerous global and regional GNSS networks provide an open access to the GNSS observations from more than 6,000 ground-based reference stations [3]. The ROTI maps with high spatio-temporal resolution constructed on multi-site dataset allow us to trace strong plasma gradients and ionospheric irregularities with the geomagnetic storm development.…”