European Space Weather Week 2025

Measuring ionospheric absorption based on received ionosonde amplitudes using sounding frequencies above 10 MHz – preliminary results

Oct 29, 2025, 8:30 AM

15m

Studion

Oral SWR4 - Interactions in the Earth’s Magnetosphere-Ionosphere-Thermosphere System and their Space Weather Impact SWR4 –Interactions in the Earth’s Magnetosphere-Ionosphere-Thermosphere System and their Space Weather Impact

Speaker

Veronika Barta (HUN-REN Institute of Earth Physics and Space Science)

Description

Space weather events like solar flares cause enhanced absorption of radio waves in the ionosphere most notably in the lowest part of it, the D-region (ca. 60–100 km altitude range) which can weaken radio signals and can pose difficulties to radio communication at certain frequencies. There exist several methods to qualitatively or quantitatively assess the absorption in the layers of Earth’s ionosphere using the different data of the ionosondes. For example based on the received amplitudes of the echoes, the D-region absorption in the ionosphere can be quantified (Buzás et al. 2023). In the current study, we present another method to utilize the upper, higher-frequency part of the spectrum (practically 10–30 MHz) of the ionosonde measurements where usually there are no reflections from the emitted electromagnetic pulses. Basically the instrument “listens” to the background noise (either of terrestrial or extraterrestrial origin) received by the antenna system at these frequencies. In this mode of measurement, it is possible to extract information on the ionospheric absorption. Here, we aim to show our preliminary results. We analyzed ionosonde amplitude data recorded at Dourbes, Sopron and Athens stations both during quiet periods and periods with M- and X-class solar flare events in 2024. The seasonal and diurnal variation of some selected frequency bands are discussed, as well as the ionospheric response at different frequencies and in the integrated frequency values during the flare events. According to the results the changes in the integrated frequency seems to be a promising way to determine the ionospheric absorption changes caused by solar flares.

References:
Buzás, A., Kouba, D., Mielich, J., Burešová, D., Mošna, Z., Koucká Knížová, P., & Barta, V. (2023). Investigating the effect of large solar flares on the ionosphere based on novel Digisonde data comparing three different methods. Frontiers in Astronomy and Space Sciences, 10, 1201625.