Open AccessIonosphere around equinoxes during low solar activity
Author(s) -
Liu Libo,
He Maosheng,
Yue Xin'an,
Ning Baiqi,
Wan Weixing
Publication year - 2010
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010ja015318
Subject(s) - ionosphere , solstice , ionosonde , radio occultation , atmospheric sciences , tec , latitude , cosmic cancer database , southern hemisphere , daytime , international reference ionosphere , northern hemisphere , altitude (triangle) , equinox , equator , physics , total electron content , electron density , geology , geodesy , climatology , geophysics , astronomy , plasma , geometry , mathematics , quantum mechanics
The seasonal behaviors of the ionosphere have been investigated for several decades, but the differences of the ionosphere between the March and September equinoxes are still an open question. In this analysis we utilize the data of ionospheric electron density ( N e ) profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission radio occultation measurements, total electron density (TEC) from TOPEX and Jason‐1, and TEC from Global Positioning System (GPS) receivers as well as global ionosonde measurements of the F 2 layer peak electron density ( N m F 2 ) to investigate the behaviors of the daytime ionosphere around equinoxes during low solar activity (LSA). The analysis reveals that during LSA the equinoctial asymmetry in ionospheric plasma density is mainly a low‐latitude phenomenon. The differences of equinoctial TEC and N m F 2 have considerable amplitudes at low latitudes in both hemispheres and less significant at higher latitudes. With increasing altitude, the asymmetry in COSMIC N e becomes weaker in the Southern Hemisphere, and the northern pronounced asymmetry regions move toward the magnetic equator. The ionospheric equinoctial asymmetry may be considered as a manifestation of the annual variation, whose annual phase significantly shifts away from the solstices. The F layer peak height ( h m F 2 ) extracted from COSMIC N e profiles also shows an equinoctial asymmetry at low latitudes, indicating the existence of equinoctial differences in low‐latitude neutral winds, specifically in the Northern Hemisphere. It reveals that, besides the important effect of the neutral wind, other processes should play roles in the forming of the observed equinoctial asymmetry in the ionosphere.