Variability of foF2 at low and middle latitudes

Variability of foF2 for an equatorial station and comparison with the foF2 maps in IRI model

“…Studies on variability vary from those that analyze specific parameters on a large geographical area, to those that are limited to a few stations or to one station. Such studies for example include those of Kouris et al (1998), Gulyaeva et al (1998), Leitinger and Hochegger (1999), Gulyaeva and Mahajan (2001), Rishbeth and Mendillo (2001), Kouris and Fotiadis (2002), Rawer et al (2003), Sethi et al (2003), Zhang et al (2004), and Gordienko et al (2005).…”

Midday bottomside electron density profiles during moderate solar activity and comparison with IRI-2001

“…Since, the bottomside electron density distribution depends upon peak ionospheric parameters (NmF2, hmF2), which themselves exhibit day-to-day variability due to several sources like solar and geomagnetic activities, energy propagation from lower atmosphere, large scale vertical atmospheric electric field, meteorological sources and seismic activities, etc. Day-to-day variability in foF2 (the critical frequency of the F2-layer) and hmF2 have been examined by various workers (Gulyaeva et al, 1998;Forbes et al, 2000;Rishbeth and Mendillo, 2001;Sethi et al, 2007aSethi et al, ,b, 2008. Apart from these, among the causes of variability that directly affects the F-region ionization at equatorial and low latitudes, is the variability in strength of the equatorial electrojet (EEJ) (Dabas et al, 2006).…”

“…and the observations were mainly due to bottomside thickness (hmF2-h0.5). Later the detail studies of parameter h0.5 were made by employing bottomside Ne-h profiles using Arecibo incoherent scatter measurements for the period of solar minimum (1974( -1977( ) (Mahajan et al, 1995. Their studies showed that during daytime for summer and equinox, (hmF2-h0.5) values based on Gulyaeva (1987) model were higher than those obtained from measurements.…”

“…This ratio varies between 0.6 and 0.8. Later, using Ne-h profiles from incoherent scatter radar measurements at Arecibo (18.4N, 66.7W, dip 50N), Mahajan et al (1995) reported that observed median values of h0.5/hmF2 varied between 0.85 and 0.8 with no major seasonal differences. In the present analysis, the seasonal variations of observed h0.5/ hmF2 during midday hours along with their medians and the IRI predicted values are illustrated in Fig.…”

Ionospheric variability at low latitude station: Hainan, China

“…It is also of practical interest since the variation of the ionosphere has an important impact on the trans-ionospheric radio communications. Many papers on ionospheric variability have been published (e.g., Radicella et al, 1993a,b;Zhang et al, 1994;Mosert de Gonzalez and Radicella, 1995;Radicella et al, 1995;Jayachandran et al, 1995;0273-1177 Zhang and Radicella, 1996;Gulyaeva et al, 1998;Forbes et al, 2000;Rishbeth and Mendillo, 2001;Kouris and Fotiadis, 2002;Ezquer et al, 2002a,b;Adeniyi et al, 2002; and many more). As we know, many practical users such as satellite designers or operators need to know not only the monthly average conditions of the ionosphere but also the expected deviations from these mean values.…”