Investigating the variation of the ionospheric absorption during large solar flares based on modern Digisonde data

0560572 - ÚFA 2023 DE eng A - Abstrakt
Buzás, A. - Burešová, Dalia - Kouba, Daniel - Mošna, Zbyšek - Barta, V.
Investigating the variation of the ionospheric absorption during large solar flares based on modern Digisonde data.
EGU General Assembly 2022. Göttingen: European Geosciences Union, 2022. EGU22-2324.
[EGU22 FAQs. 23.05.2022-27.05.2022, Vienna]
Institucionální podpora: RVO:68378289
Klíčová slova: ionosphere * gravity wave * solar flare * digisonde
Obor OECD: Meteorology and atmospheric sciences
https://doi.org/10.5194/egusphere-egu22-2324

As a result of the enhanced X-ray and EUV fluxes following large solar flares, the electron density
of the ionospheric layers increases. Furthermore, it causes higher absorption or even partial or
total fade-out of the emitted radio waves which can be measured with ionosondes and Digisondes
by studying the amplitude of the reflected electromagnetic waves [1,2].
In the present study, the ionospheric response to large solar flares has been investigated using the
ionosonde data measured at the Průhonice (Czech Republic, 49.98° N, 14.55° E) and San Vito (Italy,
40.6° N, 17.8° E) stations in September 2017, the most active solar period of Solar Cycle 24. A novel
method [3] to calculate and investigate the absorption of radio waves propagating in the
ionosphere is used to determine the absorption during large solar flare events (M and X class).
Subsequently, the absorption data are compared with the indicators derived from the fmin
method (fmin, the minimum frequency is considered as a qualitative proxy for the “nondeviative”
radio wave absorption occurring in the D-layer). Total and partial radio fade-out and increased
values (with 2–5 MHz) of the fmin parameter were experienced during and after the intense solar
flares (> M3). Furthermore, the signal-to-noise ratio (SNR) measured by the Digisondes was used
as well to quantify and characterize the fade-out events and the ionospheric absorption. The
combination of these three methods may prove to be an efficient approach to monitor the
ionospheric response to solar flares.

Trvalý link: https://hdl.handle.net/11104/0333443