Modelling of the equatorial ionospheric E-layer based on cos<img src='/image/spc_char/lembda.gif' border=0> index

Abstract

Daytime hourly values of the critical frequency of the ionospheric E-layer, <img src='http://www.niscair.res.in/jinfo/ff.gif' border=0>oE, obtained at Ouagadougou Ionospheric Observatory (12.4°N, 1.5°W) in Burkina Faso, West Africa, an equatorial station, during the solar cycle 22 (1985 – 1995) have been used to develop a model based on solar zenith angle through cos<span style="font-family:Symbol;mso-ascii-font-family:" times="" new="" roman";="" mso-hansi-font-family:"times="" roman";mso-char-type:symbol;mso-symbol-font-family:="" symbol"="" lang="EN-GB">c index factor using the relation <span style="font-family:Symbol;mso-ascii-font-family:" times="" new="" roman";mso-hansi-font-family:="" "times="" roman";mso-char-type:symbol;mso-symbol-font-family:symbol"="" lang="EN-GB"><img src='http://www.niscair.res.in/jinfo/ff.gif' border=0>oE = a (cos<img src='/image/spc_char/lembda.gif' border=0>)ⁿ_, The average value of the diurnal cos<img src='/image/spc_char/lembda.gif' border=0> index, <span style="mso-bidi-font-weight:bold">n, at Ouagadougou was found to be 0.30 for both low and high solar activity. The model was tested with <img src='http://www.niscair.res.in/jinfo/ff.gif' border=0>oE data from Korhogo (9.3°N, 5.4°W) in Cote-d’Ivoire, another equatorial station, and there is good agreement between the model and observations. The validity of the <img src='http://www.niscair.res.in/jinfo/ff.gif' border=0>oE model was also compared with predicted values by IRI-2012 model and good agreement has been observed. The percentage difference, when <img src='http://www.niscair.res.in/jinfo/ff.gif' border=0>oE observed compared with IRI-2012 model, was found to be within <img src='http://www.niscair.res.in/jinfo/ff.gif' border=0>±10% for both equinoxes and solstices for the two levels of solar activity.

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