Latitudinal responses of the ionosphere over South America during HILDCAA intervals: Case studies

Aspects regarding the influence of High-Intensity Long-Duration Continuous Auroral Electrojet Activity (HILDCAA) intervals on ionospheric dynamics have been objecting to increasing interest in the last years. Notwithstanding, some key interconnections between the HILDCAA intervals impacts on the ionosphere over distinct latitudes, according to the solar cycle phase, remain to require further investigation. In this work, the F2 layer peak height and its critical frequency (hmF2 and foF2, respectively) from Digisonde data obtained over São Luís (2.60° S; 44.21° W), Cachoeira Paulista (22.70° S; 44.98° W), and Port Stanley (51.60° S, 57.9° W), were evaluated to unravel more details of the ionospheric responses to four HILDCAA intervals as case studies. Those are equatorial, low, and mid-latitude stations, respectively, and the main results over them presented a similar trend in terms of solar cycle dependence, with the greater impact on the ionospheric density along with solar maximum conditions, despite the higher frequency of HILDCAA occurrences in the descending and minimum phases. The variation of hmF2 due to HILDCAA effects in comparison to quiet time is about 20% in equatorial and mid-latitudes, while over the low latitude station the hmF2 ranges positively up to 40%. These results enhance our understanding of the HILDCAAs magnitude degree both regarding its solar cycle occurrence, and its effects in different ionospheric latitudinal sections.