Variation of frequency of first mode of Schumann resonance under solar x-ray flashes and its relation with helio-geophysical conditions

Abstract

Properties of the Schumann resonances have been extensively studied in order to explain their relation with properties of the upper atmosphere and ionosphere. This paper presents the results of an analysis of the frequency variations of the 1st mode of the Schumann resonator in two (North-South and East-West) magnetic field components in the geophysical observatory “Mikhnevo” during solar X-ray flares of M and X classes in 2011–2017. An analysis was made for the influence of the illumination of the signal propagation path and the total electronic content on it on the response magnitude of the variation of the first Schumann resonance frequency. It is shown that the frequency variation of the first mode of the Schumann resonance depends on the helio-geophysical conditions on the signal propagation path, i.e. arc of great circle. It is also shown that the diurnal variation of the sensitivity of the frequency variation of the 1st Schumann resonance to the X-ray flash power correlates well with the diurnal variation of the total electron content of the ionosphere on the signal propagation path. This fact may indicate that the electromagnetic wave at the frequencies of the first Schumann resonance penetrates into the upper ionosphere, namely into the f-layer. And, thus, the characteristics of the F-layer of the ionosphere can affect the parameters of the first Schumann resonance.