Physics and Chemistry of the Earth, 27, 589-594, 2002.

Methodological influences on F-region peak height trend analyses

M.J. Jarvis1, M.A. Clilverd1, and Th.Ulich2

1British Antarctic Survey, Cambridge, England, U.K.
2Sodankyla Geophysical Observatory, Sodankyla, Finland.


Published estimates of the trend in hmF2 using data from ionosondes over the last 30-40 years range from +0.8 km y-1 to -0.6 km y-1 and are subject to the influence of several factors. These are considered here based upon an analysis of two southern hemisphere geomagnetically mid-latitude stations, Argentine Islands and Port Stanley. The influence of the equation used to calculate hmF2 at these stations can result in variations of +/- 0.2 km y-1; choice of solar proxy has a small influence on the end result, where using E10.7 instead of F10.7 produces changes of -0.04 km y-1; neglecting any trends in geomagnetic activity can produce variations of +0.03 to +0.2 km y-1 at the two mid-latitude stations considered in this paper; for datasets of 30-40 years length ringing due to long memory processes can produce +/- 0.2 km y-1 variability; the phase of the 11-year solar cycle, and its harmonics, captured by the datasets can cause variability of +/- 0.5 km y-1; and the neglect of local time variations in thermospheric wind conditions could result in +0.2 km y-1 for analysis which only considers local midday data. The Argentine Islands and Port Stanley datasets show ringing terms that are still converging towards trend results of -0.25 to -0.30 km y-1, which are in close agreement with the satellite drag trend estimates.