Open AccessThe ionosphere under extremely prolonged low solar activity
Author(s) -
Liu Libo,
Chen Yiding,
Le Huijun,
Kurkin Vladimir I.,
Polekh Nelya M.,
Lee ChienChih
Publication year - 2011
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 - 10.1029/2010ja016296
Subject(s) - ionosonde , ionosphere , daytime , tec , critical frequency , solar cycle , total electron content , solar minimum , environmental science , solar cycle 22 , solar maximum , atmospheric sciences , f region , international reference ionosphere , meteorology , physics , geophysics , electron density , electron , solar wind , plasma , quantum mechanics
A critical question in ionospheric physics is the state of the ionosphere and relevant processes under extreme solar activities. The solar activity during 2007–2009 is extremely prolonged low, which offers us a unique opportunity to explore this issue. In this study, we collected the global ionosonde measurements of the F 2 layer critical frequency ( f o F 2 ), E layer critical frequency ( f o E ), and F layer virtual height ( h ′ F ) and the total electron content (TEC) maps produced by the Jet Propulsion Laboratory, which were retrieved from dual‐frequency GPS receivers distributed worldwide, to investigate the ionospheric phenomena during solar minimum of cycle 23/24, particularly the difference in the ionosphere between solar minima of cycle 23/24 and the preceding cycles. The analysis indicates that the moving 1 year mean f o F 2 at most ionosonde stations and the global average TEC went to the lowest during cycle 23/24 minimum. The solar cycle differences in f o F 2 minima display local time dependence, being more negative during the daytime than at night. Furthermore, the cycle difference in daytime f o F 2 minima is about −0.5 MHz and even reaches to around −1.2 MHz. In contrast, a complex picture presents in global h ′ F and f o E . Evident reduction exists prevailingly in the moving 1 year mean h ′ F at most stations, while no huge differences are detected at several stations. A compelling feature is the increase in f o E at some stations, which requires independent data for further validation. Quantitative analysis indicates that record low f o F 2 and low TEC can be explained principally in terms of the decline in solar extreme ultraviolet irradiance recorded by SOHO/SEM, which suggests low solar EUV being the prevailing contributor to the unusual low electron density in the ionosphere during cycle 23/24 minimum. It also verifies that a quadratic fitting still reasonably captures the solar variability of f o F 2 and global average TEC at such low solar activity levels.