Studying the Effect of the Local Thunderstorm Cells on the Background ULF Magnetic Noise Parameter Spectra

Abstract

We study the effect of the masking factor from the local thunderstorm cells on ULF magnetic field spectra with the inhomogeneous electron-density structures existing in the local ionosphere (ionospheric and lower ionospheric Alfvén resonators). Using an original data-processing technique for recording of horizontal magnetic components at the midlatitude reception point Novaya Zhizn', we have examined the contribution of the sources located at different distances from the reception point to the formation of the background noise spectra. The ULF signal processing technique permitted us to reduce the pulse component of magnetic noise in amplitude above a certain threshold and thus rule out the effect of a local thunderstorm activity. Frequency dependences of the azimuthal angle of the principal axis of the magnetic noise polarization ellipse are also analyzed. It is shown that the presence of the lower ionospheric Alfvén resonator leads to a nonmonotonic dependence of the azimuthal angle on the frequency. It was found that the local thunderstorms within 60-80 km from the reception point completely mask the manifestation of the lower ionospheric Alfvén resonator in the ULF noise polarization parameters. To spot the local thunderstorm cells, we used the data from the meteorological radar facility MRL-4 in Nizhny Novgorod.

Influence of ionospheric resonators on daily dynamics of the first Schumann resonance spectral parameters according to data from a meridional chain of ULF magnetometers

“…So, the sub-IAR effect is most pronounced in the ε dynamics. The azimuth angle and its spectrum also depend on the direction to the source [Ermakova et al, 2014], and when adding fields from different sources the variations of this parameter due to the sub-IAR effect can be significantly lower than the ε variations.…”