ULF impulsive magnetic response at mid-latitudes to lightning activity

A Schekotov,E Fedorov,K Shiokawa,V Pilipenko

doi:10.5047/eps.2010.12.009

Abstract

Induction magnetometer data from the mid-latitude station Moshiri (geomagnetic latitude 35.6°) has been examined in search of a transient ULF response to the regional lightning activity. For many events, besides the main impulse produced by the lightning discharge, a secondary impulse delayed about 1 sec was observed. These secondary echo-impulses are probably caused by the partial reflection of wave energy of the initial lightning pulse from the upper boundary of the ionospheric Alfven resonator in the topside ionosphere. The modeling with artificial signals has shown that a multi-band spectral resonant structure (SRS) can be formed owing to the occurrence of paired pulses in analyzed time series. The statistical superposed epoch method indeed has revealed a dominance of two-pulse structure in the magnetic field background during the periods of the SRS occurrence.

Highlights

Electrical storms are known to be one of the natural ULF sources in the Earth’s atmosphere
Modeling Signals and Spectra Here we demonstrate that Spectral Resonant Structure (SRS) can be formed by a peculiar two-pulse structure of the disturbances produced by a local lightning activity (Fig. 8)
The statistical superposed epoch analysis has shown that magnetic disturbances during the regional lightning activity comprises regular series of paired pulses

Summary

Introduction

Electrical storms are known to be one of the natural ULF sources in the Earth’s atmosphere. A peculiar feature of the geomagnetic eld variations in the ULF band just below the fundamental tone of SR is the occurrence of Spectral Resonant Structure (SRS), observed at low (Bosinger et al, 2002), middle (Belyaev et al, 1987, 1990) and high (Belyaev et al, 1999; Yahnin et al, 2003) latitudes. Theoretical estimates have shown that the contribution of the distant world thunderstorm centers with typical charge moments of negative CG- flashes to the mid-latitude electromagnetic field in the IAR band is about two orders of magnitude less than the observed intensity (Fedorov et al, 2006). The near-by lightning (about 100 km and less from the observation site) produce too strong interference on magnetic records, and the possible SRS features cannot be revealed

Lightning-related Impulses

Comparison of Multi-pulse Structure in the IAR and SR Bands

Discussion

Conclusion