Earth Planets Space, Vol. 61 (No. 5), pp. 629-631, 2009LETTER
T. L. Gulyaeva1,2
1IZMIRAN, 142190 Troitsk, Moscow Region, Russia
2Space Research Centre PAS, Bartycka 18-A, 00-716 Warsaw, Poland
(Received October 17, 2007; Revised January 25, 2008; Accepted March 19, 2008; Online published May 29, 2009)
The F2 layer peak plasma density NmF2 is reduced by the factor constructed from the relative changes in the Sun's zenith angle χ for a particular local time and the local noon value χ0. Proposed transformation yields a proxy for the peak plasma density which coincides with the source observation at noon but apart from the latter is gradually reduced towards the night. Hourly observations at 8 ground based ionosondes for the solar maximum (2000) and minimum (2006) are analyzed for inter-stations and inter-seasonal correlation of the peak plasma density and the proxy values. The proxy values show improved correlation between the data at different locations and improved inter-seasonal correlations for a particular location due to greater homogeneity of results throughout the year contributing to improved evaluation of the ionospheric weather indices.
Key words: Ionosphere, plasma density, solar zenith angle.