Characteristics of ULF Magnetic Fields in the 3D Inhomogeneous Earth‐Ionosphere Waveguide

We develop an algorithm for calculating the characteristics of the magnetic field of signals in the frequency range of (0.1–20) Hz in the horizontally and vertically inhomogeneous spherical Earth‐ionosphere waveguide. This algorithm involves calculations of the surface impedance of an inhomogeneous ionosphere. The frequency dependences of the amplitude, phase and polarization of the magnetic field generated by a horizontal magnetic dipole were analyzed. It is shown that the horizontal inhomogeneity of the Earth‐ionosphere waveguide can significantly affect the frequency dependence of the amplitude and polarization of the magnetic field, increasing the degree of circular polarization. The horizontal inhomogeneity only slightly influences the results in daytime conditions. The most noticeable difference in the amplitude dependences of the magnetic components and large phase shifts (up to 40°) are observed when the terminator passes through the geodetic line connecting the source and receiver, and in the presence of sporadic layers with a horizontally inhomogeneous structure along the low‐frequency wave propagation path. We compare the calculation results with the magnetic pulsations recorded at Nurmijarvi station during the 2001 campaigns of Kola Peninsula ultra low frequency emitter operation. The obtained results make it possible to qualitatively explain peculiarities of the amplitude and polarization spectra of the artificial magnetic signals recorded in this campaigns that are not explained within the framework of the flat homogeneous waveguide model.

[1]  A. Ryabov,et al.  Detection of Artificial ULF Signals at Staraya Pustyn Magnetic Station during the FENICS-2019 Experiment , 2021, Geomagnetism and Aeronomy.

[2]  E. Tereshchenko,et al.  Effect of Ionosphere on the Excitation of Electromagnetic Field at Extremely Low and Lower Frequencies in the Near-Field Zone , 2018, Technical Physics.

[3]  A. Potapov,et al.  Considering the potential of IAR emissions for ionospheric sounding , 2017 .

[4]  A. V. Pershin,et al.  Effect of the Ionospheric Parameter Variations at Altitudes of 80–350 km on Diurnal Dynamics of the ULF Magnetic Field Spectra at Midlatitudes , 2017 .

[5]  M. Engebretson,et al.  Interaction of magnetospheric Alfvén waves with the ionosphere in the Pc1 frequency band , 2016 .

[6]  Q. Zhou,et al.  Pulsating nighttime magnetic background noise in the upper ULF band at low latitudes , 2014 .

[7]  E. Ermakova,et al.  Studying the Variations of the Broadband Spectral Maximum Parameters in the Natural ULF Fields , 2013 .

[8]  K. Papadopoulos,et al.  Generation of ELF and ULF electromagnetic waves by modulated heating of the ionospheric F2 region , 2012 .

[9]  E. Kopytenko,et al.  Electromagnetic sounding of the Earth’s crust in the vicinities of the SG-6 and SG-7 superdeep boreholes in the fields of natural and powerful controlled sources , 2012, Doklady Earth Sciences.

[10]  S. Polyakov,et al.  A study of resonance structures with different frequency scales in the spectrum of background extremely low-frequency noise at middle latitudes , 2012 .

[11]  N. V. Ivanov,et al.  Investigation of the peculiarities of artificial electromagnetic signal propagation at high latitudes in the range 0.1–10 Hz , 2010 .

[12]  S. Polyakov.  Artificial ionospheric source of low-frequency electromagnetic fields in the problems of environment sounding , 2008 .

[13]  U. Inan,et al.  Radiation of ELF/VLF waves by harmonically varying currents into a stratified ionosphere with application to radiation by a modulated electrojet , 2008 .

[14]  E. Tereshchenko,et al.  Effect of the ionosphere on electromagnetic waves from ground-based emitter in the frequency band 1–10 Hz , 2007 .

[15]  E. Ermakova,et al.  On a mechanism forming a broadband maximum in the spectrum of background noise at frequencies 2–6 Hz , 2007 .

[16]  S. V. Polyakov,et al.  A power line as a tunable ULF-wave radiator: Properties of artificial signal at distances of 200 to 1000 km , 2006 .

[17]  S. Polyakov,et al.  Experimental Studies of Propagation of Artificial Electromagnetic Signals in the Range 0.6–4.2 Hz , 2005 .

[18]  S. Polyakov,et al.  Excitation of Electromagnetic Waves in a Plane Waveguide with Anisotropic Upper Wall , 2003 .

[19]  V. V. Kirillov,et al.  Solving a Two-Dimensional Telegraph Equation with Anisotropic Parameters , 2002 .

[20]  Vassilis Angelopoulos,et al.  Spectral properties of the ionospheric Alfvén resonator observed at a low-latitude station (L = 1.3) , 2002 .

[21]  A. Savitsky,et al.  First Experiments on Generating and Receiving Artificial ULF (0.3–12 Hz) Emissions at a Distance of 1500 km , 2002 .

[22]  Steven A. Cummer,et al.  Modeling electromagnetic propagation in the Earth-ionosphere waveguide , 2000 .

[23]  M. Rietveld,et al.  Generation of artificial magnetic pulsations in the Pc1 frequency range by periodic heating of the Earth’s ionosphere: indications of ionospheric Alfvén resonator effects , 2000 .

[24]  D. Kotik.  ELF/VLF emissions generated in the ionosphere by heating facilities—A new tool for ionospheric and magnetospheric research , 1994 .

[25]  V. Trakhtengerts,et al.  Generation of electromagnetic signals at combination frequencies in the ionosphere , 1987 .

[26]  S. Polyakov,et al.  Excitation of the earth-ionosphere waveguide by low-frequency sources in an inhomogeneous ionosphere , 1978 .

[27]  S. J. Joubert,et al.  A crustal geoelectrical model for South African Precambrian granitic terrains based on deep Schlumberger soundings , 1975 .

[28]  V. Trakhtengerts,et al.  Mechanism of excitation of combination frequencies in ionospheric plasma , 1975 .

[29]  I. Richer,et al.  Long-range communications at extremely low frequencies , 1974 .

[30]  A. Cullen,et al.  Terrestrial propagation of long electromagnetic waves , 2013 .

[31]  V. Kirillov,et al.  Formation of a Resonance Structure of the Local Inductance of the Ionosphere at Frequencies 0.1–10 Hz , 2003 .

[32]  A. Shevtsov,et al.  INFLUENCE OF THE IONOSPHERE AND BIAS CURRENTS UPON THE RESULTS OF DEEP ELECTROMAGNETIC SOUNDINGS IN THE ELF ANTENNA FIELD , 1999 .