High historical values of foEs — Reality or artefact?

0370487 - ÚFA 2012 RIV GB eng J - Journal Article
Laštovička, Jan - Boška, Josef - Burešová, Dalia - Kouba, Daniel
High historical values of foEs — Reality or artefact?
Journal of Atmospheric and Solar-Terrestrial Physics. Roč. 74, - (2012), s. 51-54. ISSN 1364-6826. E-ISSN 1879-1824
R&D Projects: GA AV ČR IAA300420704; GA MŠMT OC09009; GA AV ČR KJB300420904
Institutional research plan: CEZ:AV0Z30420517
Keywords : Ionosphere * Sporadic-E layer * Ionospheric measurements
Subject RIV: DG - Athmosphere Sciences, Meteorology
Impact factor: 1.417, year: 2012
http://www.sciencedirect.com/science/article/pii/S1364682611002811

Very high values of foEs had sometimes been reported in the past. These values had been derived from ionograms under the assumption of vertical reflection of ordinary mode of sounding radio waves. Modern digisondes make possible to test this assumption. All hourly values of foEs > 6.0 MHz for seven summers (June 2004–August 2010) from a midlatitude station Pruhonice are selected for test, altogether 282 values. In 90% of cases the ‘‘classical’’ way of evaluation of foEs provides values higher than ‘‘true’’ values from modern digisonde (average difference about 1 MHz). 38% of ‘‘classical’’ foEs are oblique reflections, which however do not occur in direction perpendicular to geomagnetic field. The occurrence of high values of foEs varies very much from year to year between 0 and 130 events per summer. As for diurnal variation, a pronounced maximum occurs at 10:00LT and 16:00LT (secondary), and a minimum after midnight.
Permanent Link: http://hdl.handle.net/11104/0204282