Two different (and commonly used) methods of calculating the 81-day average value of the F10.7 cm solar radio flux: Impacts of global models

To enable the proper operation, planning and management of space weather services, a comprehensive and timely specification of the Earth’s upper atmosphere is required. The F10.7 cm solar radio flux is one of the most commonly used indices of solar activity and the 81-day average of this value (F10.7A) is often used to account for both short term (relating to effects of the 27-day solar rotation) and long term (solar cycle) solar variability. Two main methods of calculating F10.7A are found in modelling have been used by the scientific community, both of which have led to highly-successful results which have been published in peer-reviewed journals literature, both producing valuable results.

The present study highlights the influence of the choice of calculation method of F10.7A on ionospheric model output. The first method, centred on the day of interest, averages the preceding and following 40 days to find the value of F10.7A. The second takes a mean value of the day of interest and the preceding 80 days. Runs of Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) around the solar maxima in 2001 and 2014, using the different t the previous two solar maxima using the detailed calculation methods of F10.7A have been undertaken and the differences due to the different calculation methods evaluated. completed and the impacts on a number of parameters, such as total electron content (TEC), the neutral density, and O2/N2 ratio are presented. An example of the impact on TEC is shown in Fig. 1. The differences vary with location and can be as large as XXX TECu. With the escalating demand for accurate modelling of the Earth’s upper atmosphere, and the approaching solar maximum, the choice of calculation method of F10.7A becomes increasingly important.