Articles | Volume 35, issue 5
Regular paper
05 Oct 2017
Regular paper |  | 05 Oct 2017

Ionospheric F-region response to the 26 September 2011 geomagnetic storm in the Antarctica American and Australian sectors

Emilia Correia, Luca Spogli, Lucilla Alfonsi, Claudio Cesaroni, Adriana M. Gulisano, Evan G. Thomas, Ray F. Hidalgo Ramirez, and Alexandre A. Rodel

Abstract. The ionospheric response at middle and high latitudes in the Antarctica American and Australian sectors to the 26–27 September 2011 moderately intense geomagnetic storm was investigated using instruments including an ionosonde, riometer, and GNSS receivers. The multi-instrument observations permitted us to characterize the ionospheric storm-enhanced density (SED) and tongues of ionization (TOIs) as a function of storm time and location, considering the effect of prompt penetration electric fields (PPEFs). During the main phase of the geomagnetic storm, dayside SEDs were observed at middle latitudes, and in the nightside only density depletions were observed from middle to high latitudes. Both the increase and decrease in ionospheric density at middle latitudes can be attributed to a combination of processes, including the PPEF effect just after the storm onset, dominated by disturbance dynamo processes during the evolution of the main phase. Two SEDs–TOIs were identified in the Southern Hemisphere, but only the first episode had a counterpart in the Northern Hemisphere. This difference can be explained by the interhemispheric asymmetry caused by the high-latitude coupling between solar wind and the magnetosphere, which drives the dawn-to-dusk component of the interplanetary magnetic field. The formation of polar TOI is a function of the SED plume location that might be near the dayside cusp from which it can enter the polar cap, which was the case in the Southern Hemisphere. Strong GNSS scintillations were observed at stations collocated with SED plumes at middle latitudes and cusp on the dayside and at polar cap TOIs on the nightside.

Short summary
Ionospheric disturbances observed in Antarctica during a moderately strong geomagnetic storm caused by the impact of a coronal mass ejection from the Sun are presented here. The ionosphere behavior was analyzed using GNSS and ionosonde observations at middle and high latitudes. The results showed that the impact promptly affected the ionosphere from the Equator to the high latitudes, resulting in strong irregularities, particularly at middle and high latitudes, which can affect GPS users.