Research on the Initiation of Multiple Upward Leaders From a Single
Structure Based on an Improved Lightning Attachment Model
More and more optical records have exhibited that multiple upward
leaders (MULs) occur frequently on a structure in the flash attachment
process. An interesting issue is why a structure can continue to launch
upward leader (UL) after the first one appears. This phenomenon is
analyzed in the present paper. Considering the influence of the leader
behaviors on the ambient electric field, an improved 3-D fine-resolution
lightning attachment model with MULs is established to simulate
cloud-to-ground flash events with diverse leader spatial morphologies.
The simulation results show that MULs may initiate almost simultaneously
or with an obvious delay and the variation range of UL length is large.
From this, the flash events of lightning terminating on a structure are
divided into four scenarios and each scenario is analyzed. It can be
found that the spatial location of downward leader, the length and
propagation direction of the first UL and the time interval from the
inception of the first UL to final jump significantly affect the
electric fields at top corners of structure and further affect the
inception of the second UL. Based on qualitative analysis, four factors
are proposed to explain why the above four scenarios happen.