The Earth's electromagnetic environment

Abstract

[1] It is found that the energy density of electromagnetic fields at the surface of the Earth follow a scaling law that extends over ∼16 orders of magnitude from ∼10 −9 Hz to ∼10 7 Hz. The temporal variability of the field can be described with an ∼1/f 2 , or Brownian, noise power spectrum which reflects the superposition of numerous transient source processes. To the best of our knowledge, the spectral extent of this straightforward scaling law is unparalleled and outperforms any other scaling law in physics which describes a time dependent observable. The frequency dependence of the energy density can be approximated with the analytic description u( f ) = u 0 ( f 0 /f ) 2 where u 0 = 10Hz −1, f 0 = 1 Hz is a scaling constant, and f is the frequency of the electromagnetic field. The corresponding frequency dependence of the magnetic field is B( f ) = B 0 ( f 0 /f ) where B 0 = 10 −11 T/Hz 1/2 .

The ULF magnetic fields generated by thunderstorms: A source of ULF geomagnetic pulsations?

“…The measurements reported here confirm that thunderstorms are a strong local source of ULF magnetic field fluctuations as measured on the ground, which is an interesting and important result in the context of the sources of low‐frequency magnetic noise in the Earth's environment and the existence of a so far unexplained low‐frequency background radiation level whose amplitude varies as f − n , with n in the range 1–1.5 [ Lanzerotti et al , ; Füllekrug and Fraser‐Smith , ]. However, we also find this result interesting and potentially important in three other related contexts: (1) the charging processes and electric current flow in thunderstorms, (2) the implications of ULF electric currents/hydromagnetic waves being generated in the lower ionosphere by the thunderstorm magnetic field fluctuations, and (3) the possible effects of these hydromagnetic waves on radiation belt protons and other ions.…”

Comment on "Fractal analysis of ULF electromagnetic emissions in possible association with earthquakes in China" by Ida et al. (2012)

“…The ULF power spectrum S of a geomagnetic field component exhibits the power-law behavior S(f ) ∝ f −β , where f is the frequency (Füllekrug and Fraser-Smith, 2011). In a log S(f ) − log f representation, the power spectrum is a line having a slope β, where β is known as the spectral exponent.…”

IAR signatures in the ionosphere: Modeling and observations at the Chibis-M microsatellite

“…Electrical storms are known to be one of the natural sources of electromagnetic emissions in a wide frequency range, from ∼0.1 Hz to hundreds of MHz covering ULF-ELF-VLF-HF-VHF bands (Füllekrug and Fraser-Smith, 2011). The largest spectral density of the atmospheric electrical discharge is concentrated in the VLF band (∼few kHz), though significant spectral power is contained in the lower ELF-ULF bands (from fractions of Hz to few tens of Hz).…”