Analyzing the Effects of Geomagnetic Storms on the Ionosphere-Thermosphere System at Subauroral and Midlatitude Regions

Abstract

Understanding how geomagnetic storms affect the coupled ionosphere-thermosphere (I-T) system is crucial for space weather science and forecasting. This study examines the I-T response in subauroral and midlatitude regions during the major geomagnetic storm of 5–7 August 2011 (Solar Cycle 24), using a combination of satellite and radar observations. Neutral winds and atmospheric density data from the GOCE satellite are analyzed alongside ionospheric parameters from the Millstone Hill incoherent scatter radar (ISR) and ionosonde data (GIRO database). The results show pronounced storm-induced disturbances: enhanced westward zonal winds and increased neutral density in the thermosphere, significant uplift of the ionospheric F-layer (with evidence of a transient F3 layer), and the occurrence of midlatitude anomalies such as the Midlatitude Summer Evening Anomaly (MSEA) and subauroral polarization streams (SAPS). These observations highlight strong ion-neutral coupling during the storm’s main phase—manifested as storm-enhanced density structures and extreme ionospheric flows—and hemispheric asymmetries between summer and winter conditions. Our findings are placed in the historical context of ionospheric research: from Sir Edward V. Appleton’s pioneering discovery of ionospheric layers to modern advanced observational techniques, illustrating the evolution of the field over the past century. The study not only provides new insights into storm-time I-T dynamics at midlatitudes but also underscores how contemporary space weather research builds upon Appleton’s legacy by extending early radio probing methods to comprehensive geospace monitoring. These results have important implications for improving ionospheric models and mitigating the impacts of space weather on communication and navigation systems.

Keywords: Geomagnetic storms, Subauroral polarization streams, GOCE satellite, Incoherent Scatter Radar