Investigation of the Post‐Sunset Extra Electron Density Peak Poleward of the Equatorial Ionization Anomaly Southern Crest. Issue 10 (30th September 2022)

• Record Type: Journal Article
• Authors: Cai, Xuguang; Qian, Liying; Wang, Wenbin; McInerney, Joseph M.; Liu, Han‐Li; Eastes, Richard W.
• Is Part Of: Journal of geophysical research. Volume 127:Issue 10(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-30
• Subjects: equatorial ionization anomaly -- extra peak -- E cross B drift -- neutral wind; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2022JA030755
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The Global‐scale observation of limb and disk mission observed an extra electron density (Ne) peak after sunset at approximately 30°S near 40°W on 4 November 2019, which is poleward and immediately next to the southern equatorial ionization anomaly (EIA) crest. This Ne peak is different from previously reported mid‐latitude peaks that occur at all local times. The Whole Atmosphere Community Climate Model‐eXtended captures this phenomenon. Model diagnostic analysis reveals that the decrease of Ne and hmF2 between 15° and 25°S makes Ne near 30°S appear as an extra density peak relative to the southern EIA crest. Transport by poleward meridional wind decreases Ne between 15° and 25°S. Moreover, the upward E × B drifts due to pre‐reversal enhancement lift the plasma between the dip equator and 15°S but do not affect Ne much between 15° and 25°S with a low drift speed. Comparison with days without the extra peak shows the importance of E × B drift latitudinal variations on the extra peak formation. This study provides new insights into the dynamic variability of the nighttime ionosphere. Plain Language Summary: A whole atmosphere model from the Earth's surface to the upper thermosphere (approximately 600 km) captures qualitatively an extra electron density (Ne) peak poleward of the southern equatorial ionization crest near sunset (approximately 30°S, 40°W on 4 November 2019) observed by a far ultraviolet (FUV) instrument onboard a geostationary satellite. Model diagnostic analysis reveals that the depletion of Ne and the decrease of the Ne peak altitude (hmF2) between 15° and 25°S makes the Ne between 25° and 40°S to appear as an extra peak relative to the southern EIA crest near 15°S. The transport by the poleward meridional wind decreases Ne between 15° and 25°S. Moreover, the upward plasma drift lifts the plasma between the dip equator and 15°S but does not affect Ne much between 15° and 25°S due to the low drift speed. Consequently, Ne between 15° and 25°S decreases. Comparison with days without the extra peak also shows that the latitudinal variations of upward plasma drift play an important role in the formation of the extra peak. In summary, the observed extra Ne peak in the southern hemisphere is caused by the plasma transport by poleward meridional winds and weak upward drifts. Key Points: WACCM‐X captures the GOLD observed sunset extra NmF2 peak at approximately 30°S, 40°W that is in the poleward of the southern EIA crest on 4 November 2019 NmF2 depletion between 10° and 25°S separates the southern crest, causing the appearance of an extra peak relative to the southern crest Transport due to the poleward meridional wind with a weak vertical E × B drift (approximately 1 m/s), decrease NmF2 and hmF2 between 15° and 25°S