Analysis of Chilton ionosonde critical frequency measurements during solar cycle 23 in the context of midlatitude HF NVIS frequency predictions
Analysis of Chilton ionosonde critical frequency measurements during solar cycle 23 in the context of midlatitude HF NVIS frequency predictions
- Author(s): M.C. Walden
- DOI: 10.1049/cp.2012.0373
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- Author(s): M.C. Walden Source: 12th IET International Conference on Ionospheric Radio Systems and Techniques (IRST 2012), 2012 page ()
- Conference: 12th IET International Conference on Ionospheric Radio Systems and Techniques (IRST 2012)
- DOI: 10.1049/cp.2012.0373
- ISBN: 978-1-84919-623-9
- Location: York, UK
- Conference date: 15-17 May 2012
- Format: PDF
This paper presents a comparison of Chilton ionosonde critical frequency measurements against vertical-incidence HF propagation predictions using ASAPS (Advanced Stand Alone Prediction System) and VOACAP (Voice of America Coverage Analysis Program). This analysis covers the time period from 1996 to 2010 (thereby covering solar cycle 23) and was carried out in the context of UK-centric near-vertical incidence skywave (NVIS) frequency predictions. Measured and predicted monthly median frequencies are compared, as are the upper and lower decile frequencies (10% and 90% respectively). The ASAPS basic MUF predictions generally agree with fxI (in lieu of fxF2) measurements, whereas those for VOACAP appear to be conservative for the Chilton ionosonde, particularly around solar maximum. Below ~4 MHz during winter nights around solar minimum, both ASAPS and VOACAP MUF predictions tend towards foF2, which is contrary to their underlying theory and requires further investigation. While VOACAP has greater errors at solar maximum, those for ASAPS increase at low or negative T-index values. Finally, VOACAP errors might be large when T-SSN exceeds ~15. (6 pages)
Inspec keywords: ionospheric measuring apparatus; ionospheric electromagnetic wave propagation; solar activity; frequency measurement; ionospheric techniques; HF radio propagation
Subjects: Instrumentation and techniques for aeronomy, space physics, and cosmic rays; Ionospheric electromagnetic wave propagation; Atmospheric, ionospheric and magnetospheric techniques and equipment; Solar physics; Radiowave propagation
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