A single-station spectral model of the monthly median foF2 over Chongqing, China

T. Xu, Z. Wu, J. Wu, G. Wei, J. Feng


Hourly values of the critical frequency of the ionospheric F region, foF2, obtained at Chongqing ionospheric observatory
(geographic 29.50N, 106.40E), China, during the interval of 1977 to 1997 (solar cycle 21 and 22) have
been used to investigate the dependence of the monthly median foF2 on solar activity and geomagnetic activity,
and to construct single-station model (SSM) using Fourier expansion. The results of the present analysis show
that there is a significant nonlinear relationship between monthly median foF2 and sunspot number R especially
at daytime in each month and nighttime in summer. Furthermore, introducing geomagnetic index Ap further
improves the description of variation of monthly median foF2, and the standard deviations decrease also dependently
on time and month. Thus the complex influence of solar activity and geomagnetic activity may be approximately
expressed by a general multiple nonlinear function at Chongqing station, China. The basic aim of this
paper is to show that considering the nonlinear influence both of solar activity and geomagnetic activity improves
the monthly median model. The SSM is in good agreement with observations, with standard deviation
0.65MHz, while IRI model has a lower accuracy with standard deviation 0.96MHz.


solar cycle variation;single station model;geomagnetic index;monthly median foF2

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DOI: https://doi.org/10.4401/ag-3022
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X