Bibliography

A Synoptic-Scale Wavelike Structure in the Nighttime Equatorial Ionization Anomaly

Both ground- and satellite-based airglow imaging have significantly contributed to understanding the low-latitude ionosphere, especially the morphology and dynamics of the equatorial ionization anomaly (EIA). The NASA Global-scale Observations of the Limb and Disk (GOLD) mission focuses on far-ultraviolet airglow images from a geostationary orbit at 47.5°W. This region is of particular interest at low magnetic latitudes because of the high magnetic declination (i.e., about -20°) and proximity of the South Atlantic magnetic anomaly. In this study, we characterize an exciting feature of the nighttime EIA using GOLD observations from October 5, 2018 to June 30, 2020. It consists of a wavelike structure of a few thousand kilometers seen as poleward and equatorward displacements of the EIA-crests. Initial analyses show that the synoptic-scale structure is symmetric about the dip equator and appears nearly stationary with time over the night. In quasi-dipole coordinates, maxima poleward displacements of the EIA-crests are seen at about ± 12° latitude and around 20 and 60° longitude (i.e., in geographic longitude at the dip equator, about 53°W and 14°W). The wavelike structure presents typical zonal wavelengths of about 6.7 × 103 km and 3.3 × 103 km. The structure s occurrence and wavelength are highly variable on a day-to-day basis with no apparent dependence on geomagnetic activity. In addition, a cluster or quasi-periodic wave train of equatorial plasma depletions (EPDs) is often detected within the synoptic-scale structure. We further outline the difference in observing these EPDs from FUV images and in situ measurements during a GOLD and Swarm mission conjunction.

Rodríguez-Zuluaga, J.; Stolle, C.; Yamazaki, Y.; Xiong, C.; England, S.;

Published by: Earth and Space Science      Published on:

YEAR: 2021     DOI: 10.1029/2020EA001529

equatorial plasma bubbles; Equatorial ionization anomaly; Equatorial ionosphere; forcing from below; wave structure

Wave structures of the plasma density and vertical E$\times$ B drift in low-latitude F region

We investigate the seasonal, longitudinal, local time (LT), and altitudinal variations of the F region morphology at low latitudes using data from the first Republic of China satellite (ROCSAT-1), Global Ultraviolet Imager (GUVI), on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, and the Defense Meteorological Satellite Program (DMSP) F13 and F15 satellites. Signatures of the longitudinally periodic plasma density structure emerge before 0900 LT. The wave structure is established before noon and further amplified in the afternoon. The amplitudes of the wave structure start to diminish in the evening. The wave-4 structure is clearly distinguishable during equinox and northern hemisphere summer. During northern hemisphere winter, the density structure can be characterized to either wave-4 or wave-3 structure owing to marginal separation of the two peaks in 180°–300°E. Observations of similar density structures from ROCSAT-1 (600 km) and DMSP (840 km) at 0930 and 1800 LT indicate the extension of the wave structure to altitudes greater than 840 km. The daytime wave structure persists into the night during the equinoxes but is significantly modified during the solstices. The modification is more significant at higher altitudes and is attributed to the effects of interhemispheric winds and the prereversal enhancement. The formation of the wavelike density structure in the morning and its temporal evolution in the afternoon show a close association with the vertical E × B drift. We conclude that the E × B drift during 0900–1200 LT determines the formation of the wavelike density structure.

Kil, H.; Talaat, E.; Oh, S.-J.; Paxton, L.; England, S.; Su, S.-Y.;

Published by: Journal of Geophysical Research      Published on: Jan-01-2008

YEAR: 2008     DOI: 10.1029/2008JA013106

Equatorial ionosphere; wave structure; atmospheric tide