These mechanisms rely on extreme activity of the lightning channel to start the process ( Carlson et al . 2010 ) or on strong feedback to allow even small-scale random events to trigger production.
12.
Another hypothetical mechanism is that TGFs are produced within the thundercloud itself, either in the strong electric fields near the lightning channel or in the static fields that exist over large volumes of the cloud.
13.
Since rocks and soils already have some preexisting magnetic field, the intensity of the electric current can be determined by examining the change between the " natural " magnetic field and the magnetic field induced by the lightning current, which generally acts parallel to the direction of the lightning channel.
