24
atmosphere to a lightning discharge makes it possible to describe a number of
parameters of different components of the discharge
current by comparing the
calculation results with the observational data on electromagnetic and quasistat‑
ic fields. Analysis of the form of quasistatic field pulse made it possible to esti‑
mate the distance to the discharge, the neutralized charge and
the height of the
discharge.
One of the most important and complicated problems of the cloud physics is
the development of high-performance methods for the control of cloud-to-ground
processes and precipitation growth processes by means of active influence. The
development of scientifically grounded methods of active influence requires cre‑
ation of a new class of the cloud microstructure control models. In such models
the parameters of influence (the point of influence, the time of influence, the
source power) should be determined as the solution of the optimal control prob‑
lem for the set of equations describing transformation
of spatial and temporal
physical properties of the cloud. One of the directions of further development is
improvement of the existing models of convective clouds for studying an artifi‑
cial increase of precipitation, cloud atmosphere electrification and optimal con‑
trol of the cloud microstructure.
Experiments on modelling upward and downward leaders during the evolu‑
tion of a long spark and in an artificial electrified aerosol cloud were performed
at High-Voltage Research Centre of the All-Russian Electrotechnical Institute
[42–46]. As part of the experiments, the impact of upward and downward leaders
on lightning strokes to ground and isolated objects was studied. It was found that
in the case of the long spark, the upward negative leader is caused by a positive
downward leader propagating from the high-voltage electrode of the Marx gen‑
erator in the gap of length 9–12 m, and in the case of the electrified aerosol cloud,
the upward positive leader is initialized by the electric field of the negatively
charged cloud. All the phases typical for natural and trigger lightning were ob‑
served.
The system generating a unipolar electrified aerosol cloud and the registration
system were developed and implemented. The electrical structure of a unipolar
cloud was modelled numerically using the quasi-electrical approach. For the first
time the infrared images were obtained for the discharges generated inside the
artificial charged aerosol cloud.
Along with typical streamer and leader discharges, which are observed in
laboratory experiments with long spark discharges, inside the charged cloud
many non-conventional types of discharges were observed [45]. These discharg‑
es, named ‘stalks’, constitute a new class of discharge phenomena inside the
electrified cloud medium. The variety of stalks was classified and analysed.
To understand the physics of lightning, the studies of the kinetics of the pro‑
cesses occurring in streamer and leader discharges in plasma are important. The
E. A. Mareev, V. N. Stasenko, A. A. Bulatov, S. O. Dementyeva, A. A. Evtushenko, N. V. Ilin, ...
25
Atmospheric
Electricity
simulation of nitrogen molecules dissociation in a repetitively pulsed barrier
discharge at atmospheric pressure was presented in [47]. It was shown that the
quenching of basic predissociating conditions at this pressure is relatively low
and the use of the cross‑section of N
2
dissociation by electron impact makes it
possible to adequately describe the recovery of the atoms in these experimental
conditions at atmospheric pressure. The propagation of streamers along the gas
jets for positive and negative polarity were simulated; the resulting patterns of
the dynamics and structure of streamers in the two cases are similar to those
observed in experiments with plasma jets [48].
The influence of ionic layer formed by corona discharge at ground level in
the event of the attraction of lightning to tall objects was investigated. The prop‑
erties of non‑stationary corona supported by a multi‑point ground system in the
time-varying electric field of thunderstorms were studied numerically and ana‑
lytically. The initialization of an upward leader from the ground-based system
with natural conditions was modeled in [49].
Lightning protection remains one of the most important problems. Protection
of industrial buildings from direct lightning strokes must be combined with the
suppression of incomplete discharges from external buildings and even from
lightning rods themselves [50].
Lightning flashes are one of the main sources of nitrogen oxides in the trop‑
osphere. The nitrogen oxides can make a significant contribution to the redistri‑
bution of radiation-active and chemically active gases, which affect the variation
of the temperature fields, and thereby weather and climate change. In recent years
a series of important studies was published on the feedbacks between thunder‑
storm activity, atmospheric composition and changes in weather and climate
[51–53]. It was shown that, as the result of the variability of NOx production by
lightning and the subsequent variability of the concentrations of atmospheric
gases, temperature varies most significantly in lower and middle stratosphere in
tropical and polar regions [53].
4. Lightning location
Information being collected from a lightning location system (LLS) is appli‑
cable for solving different problems. Timely storm warning needs early thunder‑
storm detection and more precise storm cells positioning. Also, early thunder‑
storm detection may be useful for hydrological studies and the control of current
stage and trend of cloud formation. Thunderstorms are often the precursors of
other dangerous phenomena in the cloudy atmosphere; LLSs are useful for pro‑
viding aviation safety. Regional thunderstorms climatology and typical lightning
parameters, such as current magnitude and growth time, obtained by means of
LLSs, play significant role for lightning protection purposes.