Quiet Time Variation of Ionosphere Parameters near Equator | Chapter 2 | Advances and Trends in Physical Science Research Vol. 2
In recent, ionosphere has been intensively
investigated by analyzing data variability and or improving existing models for
now casting and or forecasting reasons. Therefore, the investigation of f2
layer critical frequency (fof2) parameter by means of the 2012 version of iri
(international reference ionosphere) model and tiegcm (thermosphere ionosphere
electrodynamics general circulation model) is required. The present study
appreciates the estimation of TIEGCM (Thermosphere Ionosphere Electrodynamics
General Circulation Model) and that of the 2012 version of IRI in African
Equatorial Ionisation Anomaly (EIA) region through the diurnal variation of F2
layer critical frequency (foF2). The comparison made between data and
theoretical values carried out from TIEGCM and IRI-2012 during solar cycle
minimum and maximum phases and under quiet time condition over seasons. Data
concern solar cycle 22 foF2 data of Ouagadougou station (Lat: 12.4° N; Long:
358.5°E, dip: 1.43°N for 2013) provided by Télécom Bretagne. Quiet time
condition is determined by Aa inferior or equal to 20 nT and solar cycle
maximum, and minimum phases correspond to sunspot number Rz superior to 100 and
Rz inferior to 20, respectively. Seasons are estimated by considering December
as winter month, March as spring month, June as summer month and September as
autumn month. Models predictions are better during solar maximum than during
solar minimum and strongly dependent on pre-sunrise and post-sunset periods.
The seasonal Hourly quiet time foF2 is given by the arithmetic mean values of
the five quietest day hourly values. Data profiles show noon bite out a profile
with more and less pronounced morning or afternoon peak in equinox and that
during solar maximum and that also in solar minimum except during solstice
where the profile fairly is dome or plateau. During solar minimum, both models
present a more or less pronounced afternoon peak with more or less deep trough
between 1000 LT and 1400 LT. During solar maximum, in general, TIEGCM shows
afternoon peak and IRI-2012 present plateau profile. This result exhibits the
non-well estimation of the dynamic process of this region. Model accuracy is
highlighted by the Mean Relative Error (MRE) values. These values show a better
prediction for IRI-2012 except in September for both solar cycle phases
involved. The non-good prediction of TIEGCM is observed in December during
solar minimum and in June during solar maximum. This study shows that running
IRI model enables to show that foF2 time variations present “reversed profiles”
on minimum and “plateau profile” on maximum solar cycle phases. It also shows
winter anomaly on foF2 profiles. These
different conclusions have been previously found by other authors. This work
also reports winter anomaly on foF2 parameter. The closed link between foF2 and
TEC time variations is carried out. (Winter anomaly on TEC). The study shows
Total electron contents effects on critical frequency of radio waves in the
ionosphere layer.
Biography of author(s)
Emmanuel
Nanema
Research Laboratory
for Energy and Space Weather, University of Koudougou, Koudougou BP 376,
Burkina Faso and Research Institute of Applied Sciences and Technologies
(IRSAT) CNRST, 03 BP 7047 Ouagadougou 03, Burkina Faso
Frédéric Ouattara
Research Laboratory
for Energy and Space Weather, University of Koudougou, Koudougou BP 376,
Burkina Faso.
Read full article: http://bp.bookpi.org/index.php/bpi/catalog/view/25/60/148-1
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