I had to wait a while for a UK thunderstorm.

I didn't get sharp resonances like those on Stefan's spectrogram,
except for a short period about an hour after the storm.
By that time it had moved away to the north.

H-field left hand circular:

 http://abelian.org/vlf/tmp/150822_sferic_modes_LH_25a.png

H-field right hand circular:

 http://abelian.org/vlf/tmp/150822_sferic_modes_RH_25a.png

H-field E/W loop:

 http://abelian.org/vlf/tmp/150822_sferic_modes_EW_25a.png

H-field N/S loop:

 http://abelian.org/vlf/tmp/150822_sferic_modes_NS_25a.png

Vertical E-field:

 http://abelian.org/vlf/tmp/150822_sferic_modes_VE_25a.png

On a SID monitor the resonances are visible up to 40kHz or
more, and there may be a hint up to 70kHz.  I need to work
on that to try to bring them out.

--
Paul Nicholson
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