Statistical characterisation of spread F over South Africa
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Date
2011
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Abstract
The occurrence of mid-latitude spread F (SF) over South Africa has not been extensively studied since the installation of the DPS-4
digisondes in 1996 and 2000 at Grahamstown (33.32 S, 26.50 E) and Madimbo (22.38 S, 30.88 E) respectively. This study is intended
to quantify the probability of occurrence of F region disturbances associated with SF over South Africa. A study was conducted using
data for 8 years (2001–2008) over Madimbo (with a time resolution of 30 min) and Grahamstown (with a variable time resolution of 15
and 30 min). In this study, SF has been classified into frequency SF (FSF), range SF (RSF) and mixed SF (MSF). The SF events were
identified by manually identifying ionograms showing SF and tabulating them according to type for further statistical analysis. The
results show that the diurnal pattern of SF peaks strongly between 01:00 and 02:00 local time, LT (LT = UT + 2 h), where UT is the
universal time. This pattern is true for all seasons and types of SF at Madimbo and Grahamstown in 2001 and 2005, except for RSF
which had peaks during autumn and spring in 2001 at Madimbo. The probability of both MSF and FSF tends to increase with decreasing
solar activity, with a peak in 2005 (a moderate solar activity period). The seasonal peaks of MSF and FSF are more frequent during
winter months at both Madimbo and Grahamstown. In this study, SF was evident in 0.03% and 0.06% of the available ionograms at
Madimbo and Grahamstown respectively during the 8 years.
Description
Keywords
Mid-latitude spread F, Diurnal variation, Seasonal variation, Ionospheric irregularities
Citation
Amabayo, E. B., McKinnell, L. A., & Cilliers, P. J. (2011). Statistical characterisation of spread F over South Africa. Advances in space research, 48(12), 2043-2052. doi:10.1016/j.asr.2011.08.029