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 Alfven 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 Alfven 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 Alfven 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.