Characteristics of pulse trains observed during the initial stage of high peak current winter flashes

0558916 - ÚFA 2023 DE eng A - Abstrakt
Kolmašová, Ivana - Santolík, Ondřej - Pedeboy, S. - Kolínská, Andrea - Amrich, Samuel - Lán, Radek - Uhlíř, Luděk
Characteristics of pulse trains observed during the initial stage of high peak current winter flashes.
EGU General Assembly 2022. Göttingen: European Geosciences Union, 2022. EGU22-3752.
[EGU22 FAQs. 23.05.2022-27.05.2022, Vienna]
Institucionální podpora: RVO:68378289
Klíčová slova: cloud-to-ground lightning flashes * winter thunderclouds
Obor OECD: Fluids and plasma physics (including surface physics)
https://doi.org/10.5194/egusphere-egu22-3752

Our study aims at initial stage of energetic negative cloud-to-ground (CG) winter lightning flashes.
We analyze broadband magnetic-field measurements recorded in the West Mediterranean region
in winter 2014/2015. By combining our data with information provided by the French national
lightning locating system MÉTÉORAGE, we were able to select 200 waveform captures, which
contained return stroke (RS) pulses emitted by negative CG discharges with peak currents
exceeding 100 kA. The frequency band of our instrumentation (5 kHz-90 MHz) allowed us to
investigate fine details of recorded waveforms. We found that the winter pre-stroke processes
were very short, lasting on average only 1.7 ms from the first bipolar preliminary breakdown (PB)
pulse to the following return stroke pulse. The amplitudes of the strongest PB pulses reached on
average only 25 % of the corresponding RS pulse. We investigate the evolution of peak amplitudes
and inter-pulse intervals of PB pulses within individual PB trains. We found that in some trains the
amplitudes of pulses were nearly monotonically increasing with time, they reached a maximum in
a few hundreds of microseconds, and then decreased again being relatively regularly distributed
in time. Within other PB trains, the pulses were chaotically spaced and their peak amplitudes did
not show any trend. We assume that the short duration of the pre-stroke process indicate strong
electric fields inside winter thunderclouds and hypothesize that the time evolution of PB pulse
amplitudes and interpulse intervals reflect the spatial arrangement of the negative charge region.

Trvalý link: https://hdl.handle.net/11104/0332408