PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
Model
We compute waveforms directly in the time domain for the uniform Earth – ionosphere cavity
model. The ‘linear’ propagation constant is used ν ( f ) = ( f − 2) 6 − i f 100 that was found from the
Schumann resonance cross-spectra measured at large longitudinal separation of two observatories
[Nickolaenko and Hayakawa, 2002]. Computations were performed with the algorithm accelerating the
convergence of time series.
Fig.3. Evolution of E – and H – pulses with the source distance. Signal focusing is obvious around the source
antipode.
A flat infinite frequency response of the receiver was assumed. Figure 3 depicts a series of
pulsed waveforms computed for a set of source – observer distances ranging from 2 to 20 Mm. The
field increase is clearly seen at the vicinity of antipodal distance of 20 Mm. We used the ‘white’
source current moment of a lightning discharge with Ids (f) = 10 8 A*m. The above current moment
is related to a stroke with the peak current of 25 kA and the channel length of 4 km. Since we
compare experimental and computational waveforms, the particular source amplitude is
insignificant. The stroke polarization was positive. Visual comparison of pulse amplitudes indicates
that the above current moment underestimates the observed value by a factor of up to five, which is
in agreement with regular Q-bursts observations.
Comparison of experimental (black) and model (color) data
Frames below present individual pulses: black lines depict the results observed and the model data
are shown by the red dotted lines. The time is shown along the abscissa, and the pulse middle sub-peaks were
aligned to facilitate the comparison. The major feature of all data sets was their high reciprocity. Once the
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