Solar variations in extremely low frequency propagation parameters: 1. A two‐dimensional telegraph equation (TDTE) model of ELF propagation and fundamental parameters of Schumann resonances

Abstract

[1] The primary purpose of the research presented is to study solar variations in extremely low frequency (ELF) propagation parameters using Schumann resonance (SR) data from our irregular observations carried out in the East Carpathian mountains. The natural electromagnetic ELF fields in the Earth-ionosphere cavity (the global resonator) are strongly dependent on its resonance and propagation properties as well as on the global thunderstorm activity. Thus a determination of the global resonator parameters from Schumann resonances needs information about such signal properties, which depend only on physical conditions of the Earth-ionosphere cavity. To seek such signal properties, we consider the two-dimensional telegraph equation (TDTE) approach for describing propagation of ELF electromagnetic waves in a two-dimensional spherical transmission line model of the Earth-ionosphere cavity. We have set up a model consisting of a network of finite, homogeneous, one-dimensional transmission lines covering the sphere; with the square root dependence of the attenuation rate from frequency as a sufficient model for the study of the solar influence on global properties of the Earth-ionosphere cavity. Using this model, we have constructed useful formulae and algorithms connecting the observed parameters of Schumann resonances with the attenuation rate. This enables us to study the solar influence on the attenuation rate from diurnal observations of the NS-magnetic component of the ELF field measured at one station. As the measurements were carried out during both the minimum and the maximum of the solar cycle 23, we present in the work of KuÀ lak et al. [2003] evidence for a change in the ELF attenuation rate in the Earth-ionosphere cavity with solar activity.

Solar variations in extremely low frequency propagation parameters: 2. Observations of Schumann resonances and computation of the ELF attenuation parameter

“…In Table 1 we present the observation log together with some characteristic Schumann resonances parameters calculated using our TDTE transmission line model (paper 1) as well as the solar data. First, the daily average values given in columns 8, 9, and 10 have been computed according to the following procedure:…”

“…We have chosen the north‐south component of the magnetic field because from our East Carpathian station both Asia and America thunderstorm centers are so far away that in our measurements we can await signals generated at large distances. The observation of these signals is needed if we want to use the spectral method described in paper 1 for the determination of the attenuation rate. If isotropic waveguide response is upheld, we expect the horizontal magnetic field from vertical lightning current in America and Asia to have a dominant north‐south component in the Carpathians while the African lightning is expected to produce a dominant east‐west magnetic field.…”

“… Observations of resonant electromagnetic fields caused by global lightning activity are employed in determining the averaged parameters of the lower ionosphere. Using the two‐dimensional telegraph equation (TDTE) transmission line model described by Ku ak et al [2003], we have computed the attenuation rate of the Earth‐ionosphere waveguide from diurnal observations of the N‐S magnetic component of the ELF field performed irregularly for 6 years in the East Carpathian mountains. As the measurements were carried out during both the minimum and the maximum of the solar cycle 23 we present how solar activity influence the first Schumann resonance frequency and the attenuation rate.…”

Imprints of Natural Phenomena and Human Activity Observed During 10 Years of ELF Magnetic Measurements at the Hylaty Geophysical Station in Poland

“…Information contained in the amplitudes of the SchR peaks allows one to study global and continental thunderstorm activity (Nieckarz et al 2009, Dyrda et al 2014. In the meantime, the analysis of frequency changes permits the study of the condition of the Earth-ionosphere cavity (Sátori et al 2007) and its changes due to exposure to the Sun (Kulak et al 2003, Sátori et al 2005. …”

The design and the performance of stratospheric mission in the search for the Schumann resonances

“…For summary see also [9]. This design was used to observe ELFs on the ground [10,11,12,13]. It was supplied with a Chebyshev filter reducing aliasing.…”