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Atypical Sporadic (Es) layer type was detected for the first-time during nighttime in the South American Magnetic Anomaly
Digisonde data and simulations show the extra ionization that occurred in the main phase of the strong magnetic storm on 11 May 2024
The E region presence enabled the formation of the cusp-type Es layer (Esc), which had only been seen during daytime periods until now
Abstract:
Digisonde data showed a peculiar behavior in the nighttime lower ionosphere over Cachoeira Paulista (CXP, 22.7°S, 45°W, dip ∼35°), a low-latitude station located inside the South American Magnetic Anomaly (SAMA) during the main phase of the extreme magnetic storm on 11 May 2024. The E region appeared in observational data at high altitudes after sunset, which is unexpected. In sequence, it performed an unusual descending movement due to the disturbed electric field. The extra ionization responsible for forming the nocturnal E layer is due to the precipitation (EPP) of low energic (<30 keV) particles. Moreover, a diurnal cusp-type Es layer (Esc) appeared simultaneously, which has never been reported in the literature at such hours. Thus, the results further suggest that the EPP may have caused an oscillation in the thermosphere, forming the Esc usually seen in the daytime. Therefore, this study shows the different mechanisms acting together during this magnetic storm, creating a daytime ionosphere after sunset over the SAMA region, as confirmed by observational data and simulations.
