خلاصة:
Ionospheric slab thickness is defined as the ratio of TEC to maximum electron density of the F-region (NmF2), proportional to the square of the F2-layer critical frequency (foF2). It is an important parameter in that it is linearly correlated with scale height of the ionosphere, which is related to electron density profile. It also reflects variation of the neutral temperature. Therefore, ionospheric slab thickness is a significant parameter representative of the ionosphere. In this paper, the International Reference Ionosphere (IRI) model, South African Bottomside Ionospheric Model (SABIM), and measurements from ionosondes in the South African Ionosonde Network were combined within their own limitations to develop a map of foF2 values for the South African region. This parameter and vertical TEC values derived from the map using the IRI model were used to compute ionospheric slab thickness. Finally climatology of the slab thickness is described by diurnal and seasonal variations.
ملخص الجهاز:
In this paper, the International Reference Ionosphere (IRI) model, South African Bottomside Ionospheric Model (SABIM), and measurements from ionosondes in the South African Ionosonde Network were combined within their own limitations to develop a map of foF2 values for the South African region.
This parameter and vertical TEC values derived from the map using the IRI model were used to compute ionospheric slab thickness.
The ionospheric slab thickness is a parameter which provides information about the nature of the distribution of ionization at a specific location and is defined as the ratio of the vertical Total Electron Content (TEC) measured in TEC units to the maximum ionospheric electron density in the F-region (NmF2).
, 1986; Davies and Liu, 1997; Gulyaeva et al.
For this purpose, a map of foF2 values for the South African region was developed and then used to adapt the International Reference Ionosphere (IRI) model to generate vertical total electron content for this region.
2. Study Area The data sources considered for the development of the map are the IRI model, SABIM, and measured data from the 4 South African ionosonde stations.
After producing foF2 and VTEC values, the ionospheric slab thickness in kilometers can be calculate as follow: (View the image of this page) where T EC in T ECu and N F 2 is the peak electron density in the F2-region.
Figure 4 a to d illustrate variations in the South African ionospheric slab thickness during the 4 seasons of year 2008.