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Longitudinal Variations of the Occurrence Probability of the Ionospheric F 1 Layer Peak at Middle and High Latitudes
Author(s) -
Li Zhenxing,
Luan Xiaoli,
Ren Dexin
Publication year - 2019
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2018ja026236
Subject(s) - longitude , ionosphere , latitude , daytime , thermosphere , atmospheric sciences , middle latitudes , f region , local time , low latitude , geology , environmental science , climatology , geodesy , geophysics , mathematics , statistics
This study focuses on the longitudinal variations of the ionospheric F 1 layer occurrence probabilities from middle to high latitudes (40–70°) in the daytime in summer under low solar activity conditions. The ionospheric electron density profiles retrieved from the Constellation Observing System for Meteorology, Ionosphere, and Climate observations are used. The patterns of the F 1 layer occurrence probabilities are constructed with latitude, longitude, and local time in both hemispheres. The results illustrate a new feature that the occurrence probability of the F 1 layer changes with longitude in both hemispheres. Specifically, the F 1 layer generally occurs more frequently in the longitudes within ~160°E–90°W at 40–70°N and within 0–150°E at 40–70°S. The peak occurrence probabilities occur around 150°W (>0.6) and 60°E (>0.8) in the Northern and Southern Hemispheres, respectively. The valleys with values near 0 are located at about 120°W at 40–70°S. A minor peak (~0.4) also occurs within ~0–90°E at 40–70°N. These locations depend on latitude and local time. A simulation using the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) reproduces the observed longitudinal pattern well. Further TIEGCM simulations show that the higher F 1 layer occurrence probabilities can be largely explained by longitudinal variations of the O/N 2 ratios and also that the dynamic processes, such as the neutral winds above the F 1 layer, have additional contributions. These results reveal that the low O/N 2 ratios deplete the ionospheric electron density above the F 1 layer at middle and high latitudes and thus makes the F 1 layer stand out.