Spatial correlation between lightning strikes and whistler observations from Tihany, Hungary

  • J. Öster School of Physics, University of KwaZulu-Natal, Durban 4041, South Africa. Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden. Department of Astronomy and Space Physics, Uppsala Universit
  • A. B. Collier School of Physics, University of KwaZulu-Natal, Durban 4041, South Africa. Hermanus Magnetic Observatory, Hermanus 7200, South Africa.
  • A. R.W. Hughes School of Physics, University of KwaZulu-Natal, Durban 4041, South Africa.
  • L. G. Blomberg Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
  • J. Lichtenberger Space Research Group, Eötvös University, Budapest Pf 32 H-1518, Hungary.

Abstract

A whistler is a very low frequency (VLF) phenomenon that acquires its characteristics from dispersive propagation in the magnetosphere. Whistlers are derived from the intense VLF radiation produced in lightning strikes, which can travel great distances within the Earth-ionosphere waveguide (EIWG) before penetrating the ionosphere, and exciting a duct. Field-aligned ducts of enhanced plasma density guide the propagation from one hemisphere to the other. The location of the duct, relative to the strike that causes the whistler, is unknown. Whistler time series from Tihany, Hungary, have been cross-correlated with lightning data obtained from the World Wide Lightning Location Network (WWLLN). The results show that whistlers observed at Tihany originate mainly from lightning strikes in an area with a radius of approximately 1 000 km surrounding the magnetic conjugate point in the Indian Ocean just east of East London, South Africa. A clear diurnal distinction was seen in that the correlation is maximised when the whistler station and the source region are in darkness. This is believed to relate to the diurnal variation of the ionosphere, which becomes more transparent to VLF waves at night.