Geoscience Reference
In-Depth Information
With
Nm
∗
E
=
NmE
−
N
F
1
(
hmE
)
−
N
F
2
(
hmE
),
Nm
∗
F
1
=
NmF
1
−
N
E
(
hmF
1
)
−
N
F
2
(
hmF
1
),
(59)
and
exp
10
ξ(
h
)
=
.
(60)
1
+
1
|
h
−
hmF
2
|
is a function assuring a fadeout of the E and F1 layers in the proximity of the
F2 layer peak in order to avoid the second maxima around
hmF
2. The
Nm
values are
obtained from the critical frequencies obtained from the ionograms. The peak height
of the F2 layer
hmF
2 is computed from
M
ξ(
h
)
foE
.The
F1 peak height
hmF
1 is modeled in terms of
NmF
1.The geomagnetic dip of the
location and the E peak height
hmE
is fixed at 120km. The thickness parameter
B
2
of the F2 layer is calculated using the empirical determination of the base point of
the F2 layer defined by Mosert de Gonzalez and Radicella (
1990
) and the thickness
parameters corresponding to the Fl and E regions are adjusted numerically (Radicella
and Leitinger
2001
).
The NeQuickmodel gives electron density as a function of geographic latitude and
longitude, height, solar activity (specified by the sunspot number or by the 10.7 cm
solar radio flux), season (month) and time (Universal or local) (Radicella
2009
).
The Fortran-77 source code of the NeQuick model is available at Radiocommuni-
cation Sector website (ITU
2011
). The basic inputs of the code are: position, time
and solar flux (or sunspot number) and the output is the electron concentration at
any given location in space and time. In addition the NeQuick package includes
specific routines to evaluate the electron density along any ray-path and the corre-
sponding TEC by numerical integration (Nava
2006
). The first version of the model
has been used by the European Space Agency (ESA), European Geostationary Nav-
igation Overlay Service (EGNOS) project for assessment analysis and has been
adopted for single-frequency positioning applications in the framework of the Euro-
peanGalileo project. It has also been adopted by the International Telecommunication
Union, Radiocommunication Sector (ITU-R) as a suitable method for TECmodeling
(ITU
2007
).
(
3000
)
F
2 and the ratio
foF
2
/
4.1.3 IRI Model
The International Reference Ionosphere (IRI) is the result of an international coopera-
tion sponsored by the Committee on Space Research (COSPAR) and the International
Union of Radio Science (URSI). Since first initiated in 1969, IRI is an internationally
recognized standard for the specification of plasma parameters in Earth's ionosphere.
It describes monthly averages of electron density, electron temperature, ion temper-
ature, ion composition, and several additional parameters in the altitude range from
60 to 1500km. IRI has been steadily improved with newer data and better modeling
