Different Sporadic‐E (Es) Layer Types Development During the August 2018 Geomagnetic Storm: Evidence of Auroral Type (Es<sub>a</sub>) Over the SAMA Region
Juliano Moro, Jiyao Xu, C. M. Denardini, L. C. A. Resende, L. A. Da Silva, Sony Su Chen, A. J. Carrasco, Z. Liu, Chi Wang, Nelson Jorge Schuch
Abstract
Abstract Sporadic‐E (Es) layers are investigated over five Digisonde stations located inside (Santa Maria and Cachoeira Paulista), boundary (São Luís), and outside (Millstone Hill and Port Stanley) the South American Magnetic Anomaly (SAMA) in the course of the 25 August 2018, geomagnetic storm. Data from Digisondes and ground‐based magnetometer and a numerical model of the E ‐region (MIRE) are analyzed to search the roles of neutral winds and electric fields as physical processes responsible for the generation of Es layers. Moreover, it is observed for the first time over Santa Maria a type of Es layer that resembles the Es a detected in the auroral region. The characterization of such signatures in ionograms and the investigations of its formation mechanism are the main focus of this study. Hiss waves activities detected by the Van Allen Probe‐B data provide evidence that energetic particle precipitations are the most likely process responsible for this type of Es layer inside the SAMA in the night hours during the geomagnetic storm recovery phase. An attempt is also made to explain the presence of Es q over São Luís in terms of the expansion of the Equatorial Electrojet to higher latitudes. Finally, the results bring a new observational and modeling indication of a concomitant action of multiple formation mechanisms in the Es layers development in the American sector during the 25 August 2018, geomagnetic storm.