@Article{ChaitanyaPatrBalaRao:2016:UnBeLo,
author = "Chaitanya, P. Pavan and Patra, A. K. and Balan, Nalan and Rao, S.
V. B.",
affiliation = "{National Atmospheric Research Laboratory} and {National
Atmospheric Research Laboratory} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and University, Tirupati",
title = "Unusual behavior of the low-latitude ionosphere in the Indian
sector during the deep solar minimum in 2009",
journal = "Journal of Geophysical Research: Space Physics",
year = "2016",
volume = "121",
number = "7",
pages = "6830--6843",
month = "July",
keywords = "deep solar minimum, equatorial ionosphere.",
abstract = "In this paper we carry out a comparative study of the daytime
(7-18 LT) behavior of the near-equatorial ionospheric F region at
the end of the long deep solar minimum (2009) with respect to that
of the previous normal solar minimum (1995) in the Indian
longitude sector using ionosonde observations of F layer
parameters, radar observations of ExB drift, and the IRI-2012
(International Reference Ionosphere-2012) model. We investigate
the F-2 and F-3 layer behaviors separately. The results reveal
that the peak frequencies of the F layer (f(peak)), F-2 layer
(f(o)F(2)), and F-3 layer (f(o)F(3)) in 2009 are consistently
lower than those in 1995. Maximum difference in
f(peak)/f(o)F(2)/f(o)F(3) between 2009 and 1995 observations is
found in the equinoxes followed by winter and summer. The annual
mean, seasonal mean, and 10day mean peak electron density
(corresponding to f(peak)) in 2009 were lower than those in 1995
by as much as 34%, 46%, and 65%, respectively. Solar rotation
effect is less conspicuous in 2009 than in 1995, consistent with
the solar rotation signature in F-10.7. Observations also show
considerable amount of equinoctial asymmetry in electron density,
which is found to be closely linked with the corresponding
asymmetry in the vertical ExB drift. Seasonal mean peak electron
densities of the F layer (corresponding to f(peak)) and the F-2
layer (corresponding to f(o)F(2)) observed during the deep solar
minimum of 2009 were smaller than those corresponding to IRI-2012
model f(o)F(2) by as much as 45% and 50%, respectively,
underlining the need to incorporate the data collected during the
long deep minimum in the IRI model. The unusually weak ionosphere
observed in 2009 is discussed in terms of the direct effect of the
low solar EUV flux in 2009 as compared to 1995 and its indirect
effects on ionospheric electric field, thermospheric composition
(or O/N-2 ratio), and thermospheric neutral winds.",
doi = "10.1002/2015JA022061",
url = "http://dx.doi.org/10.1002/2015JA022061",
issn = "2169-9380",
language = "en",
targetfile = "chaitanya_unusual.pdf",
urlaccessdate = "27 abr. 2024"
}