Longitudinal variation in E- and F-region ionospheric trends

A novel technique is used to examine northern hemisphere midlatitude longitudinal variations in ionospheric long-term trends. Differences in hour-by-hour monthly median ionospheric parameters between equilatitudinal observatory pairs are analysed for long-term trends, thus eliminating at source the large solar cycle and geomagnetic variability that normally hinders ionospheric trend calculations. The results confirm the finding of Bremer [1998. Trends in the ionsopheric E- and F-regions over Europe. Annales Geophysicae 16, 698-996] that there are longitudinal variations in the F-region altitude trend across Europe, but suggest the influence of a stationary wave-like feature between 3 degrees W and 104 degrees E. Possible causes such as scaling errors, insufficient account of changes in ionisation underlying the F-region, varying gravity wave fluxes, and secular change in the geomagnetic field are ruled out. The data suggest that the longitudinal variation may reflect long-term changes in a large-scale stationary feature induced via non-migrating tides induced by latent heat release in the troposphere.Significant differences in the long-term trend of E-region peak plasma frequency between observatories were also found. These E-region differential trends varied with solar zenith angle reaching over 0.3 MHz per decade between Juliusruh and Moscow at midday in summer. (C) 2008 Elsevier Ltd. All rights reserved.

Details

Publication status:
Published
Author(s):
Authors: Jarvis, Martin J.

Date:
1 January, 2009
Journal/Source:
Journal of Atmospheric and Solar-Terrestrial Physics / 71
Page(s):
1415-1429
Digital Object Identifier (DOI):
https://doi.org/10.1016/j.jastp.2008.05.017