Contribution to ionospheric F2 region long-term trend studies through seasonal and diurnal pattern analysis

A. JUAN

GLOBAL AND PLANETARY CHANGE

ELSEVIER SCIENCE BV

Año: 2023 vol. 229

0921-8181

The ionosphere’s long-term trends have been studied since 1989, with a particular focus on the F2 region’sparameters due to their importance in space weather and radio signal propagation research. The accuracy andattribution of trends, particularly for the critical frequency foF2, have been controversial due to methodologicalissues and identification of the sources, such as greenhouse gases concentration increase, natural forcings, or acombination of them. The present work analyzes these current concerns by considering foF2 measured at mid-tolowlatitude stations across the globe covering up to the most recent full year, 2022. Seasonal and diurnalvariability of the trends were assessed by analyzing the relative roles of two potential drivers: increasinggreenhouse gases concentration and geomagnetic field secular variation using a simple theoretical analysis. Theresults show overall negative trends with the most negative values around equinox and the weakest, or slightlypositive trends in December–February or June–August, respective of the winter hemisphere. The general diurnalpattern evinces the most negative values in daytime hours and the weakest during nighttime. Studying andunderstanding these trends and their possible sources will contribute to the broader research area of climatechange, which is taking place in all the layers of the Earth’s atmosphere.