Optimum solar proxy for long-term ionospheric investigations

Jan Lastovicka - Institute of Atmospheric Physics, Czech Academy of Sciences

Session: Thermosphere-Ionosphere Interactions and Effects

Abstract

The problem of optimum solar proxy is important for long-term and/or climatological studies of ionospheric parameters as well as for modeling. I focus on possibly different optimum solar proxies for different ionospheric parameters, as they are affected by partly different spectral ranges of solar ionizing radiation. I use yearly average values of foF2 and foE of four European stations with long (1976-2014) and high-quality data (Juliusruh, Pruhonice, Rome, Slough/Chilton), and the global total electron content (G-TEC). Four solar proxies are used: F10.7, Mg II, solar Lyman-alpha flux Fα and sunspot numbers R. The most important finding is that the optimum solar proxies are different for different ionospheric parameters. The most suitable solar proxy for foF2 is found to be Mg II, whereas for foE F10.7 evidently outperforms Mg II. Fα and sunspot numbers perform slightly worse but none of four solar proxies performs poorly. F10.7 is favored for G-TEC, to some extent surprisingly, as previous results favored rather Mg II. However, also Fα and R provide results which are not significantly worse than those based on F10.7 and Mg II.