Atmospheric Electricity - Ultra and Extremely Low Frequency Electromagnetic Fields - page 77

Fig. 3.17 ThesameasinFig. 3.4 but for the thunderstorm QE field preceding a GJ discharge
(Surkov and Hayakawa 2012 )
patterns of GJs are similar to inverted images of conventional CG (Pasko 2010 ;
Neubert et al. 2011 ). Despite this similarity the other parameters of GJs differ
significantly from those of standard CG. For example, a GJ recently observed by
Cummer et al. ( 2009 ) was estimated to transfer the negative charge of 144 C from
the thundercloud to the lower ionosphere. This value is much greater than a typical
charge 5-10 C lowered to the ground by a normal CG stroke. Additionally,
the onset time of the GJ current was about 30 ms which is much greater than that
( 5 s) due to the stroke. This kind of GJ can be referred to as the class of negative
cloud-to-ionosphere discharge ( CI)
The first documented event of positive cloud-to-ionosphere discharge ( C CI) has
been recently observed by van der Velde et al. ( 2010 ) during winter thunderstorms
in the Mediterranean. This event is characterized by the current peak value of
3:3 kA and by short duration of 120-160 ms. This C CI discharge was estimated to
lower negative charge 136 C down from the ionosphere to the positively charged
origins in the cloud only 6:5 km tall that result in a huge charge moment change
of 11,600 C km. This event has also demonstrated that high altitudes are not a
necessary condition for initiation of GJs.