Ionospheric-equivalent slab-thickness and peak height at the F2 region
of equatorial latitude over West Africa.
Abstract
At the equatorial latitude of a West African station (8.50N, 4.68E), we
have examined the slab-thickness (τ) relative to peak electron density
height (hmF2) at F2 layer, employing Digisonde Portable Sounder τ
(DPS-τ) and Global Positioning System τ (GPS-τ) during the low solar
activity year 2010. Our observation revealed maximum and minimum τ
during the daytime and nighttime respectively, which may indicate
maximum and minimum scale height in τ through daytime and nighttime,
respectively. The discrepancies between the together reversed signatures
of DPS-τ and GPS-τ around 0100 - 0600 LT in June could indicate the
failure to incorporate a reflection of the composition changes in the
topside-DPS model. We have reported the pre-sunrise and post-noon peaks
in GPS-τ and hmF2, which are contributions of plasmaspheric TEC and
pre-reversal enhancement (PRE) velocity, respectively. Around 1100 -
1700 LT, the stability in hmF2 show that the interaction of neutral wind
and eastward electric field could be employed to predict the τ. We also
reported that the pre-sunrise increase in GPS-τ is not an indication of
PRE velocity as observed during the nighttime. The relationship between
τ and hmF2 gives a high correlation coefficient (CC), but CC during the
daytime is higher than the nighttime values which suggest the constant
diffusion state of plasmasphere during the daytime whereas the nighttime
is a function of the plasmaspheric flow of electron content and PRE
velocity. We compared the experimental hmF2 with IRI-2016 and found that
the IRI-2016 model is incapable of capturing the post-sunset and
pre-sunrise increases.