Ionospheric Chaos in Solar quiet Current due to Sudden Stratospheric Warming Events Across Europe-Africa Sector

Abstract. This study examines the ionospheric chaos in the solar quiet current, across Europe and Africa sectors during 2009 and 2021 Sudden Stratospheric Warming (SSW). The SSW was categorized into precondition, ascending, peak, descending, after and no-SSW phases based on the rising stratospheric temperature. Thirteen magnetometer stations, located within the geographical longitude of 26° to 40° across Europe and Africa sectors were considered. The magnetometer data obtained during the periods of SSW were used to derived the ionospheric solar quiet current time series. This solar quiet current time series was transformed into a complex network representation using the Horizontal Visibility Graph (HVG) approach and Fuzzy Entropy was employed on the transformed solar quiet current time series to quantify the presence ionospheric chaos during the periods of SSW. The results revealed that the latitudinal distribution of entropy depicts high entropy values indicating the presence of ionospheric chaos in most of the stations situated within the European sector compared to stations in the African sector. A consistent low entropy values unveiling the presence of orderliness behavior was found to be prominent in the Africa sector. This dominance of orderliness behavior in the Africa sector during SSW means that the influence of SSW on the regional ionosphere of this sector is minimal. However, the pronounced features of ionospheric chaos found in the European sector reveal evidence of significant effects of SSW on the regional ionosphere in this sector. Finally, we found that after the peak phase of SSW, the ionospheric chaos is more pronounced.