Earth Planets Space, Vol. 63 (No. 2), pp. 119-128, 2011
A. Schekotov1, V. Pilipenko1, K. Shiokawa2, and E. Fedorov1
1Institute of the Physics of the Earth, Moscow
2STEL, Nagoya University, Japan
(Received August 31, 2010; Revised December 1, 2010; Accepted December 14, 2010; Online published February 28, 2011)
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.
Key words: Lightning, Pc1 waves, ionosphere, Alfven resonator, spectral resonant structure.