On a Possible Mechanism of Space Stem Formation in Negative Long Sparks

Xiangen Zhao, N. A. Popov, Quan Gan, Yuxuan Ding, Ya Ping Du, Junjia He

Research output: Journal article publicationJournal articleAcademic researchpeer-review

1 Citation (Scopus)


To study the mechanism of space stem formation, the high-speed direct imaging technique and Schlieren photography are used to simultaneously observe the space stems in a 1.35-m air gap under the lightning impulse voltage. It is found that the average length and diameter of the space stem is approximately 5 and 0.5 mm, which is about 1/3 of the length and 1/10 of the diameter of the local luminous region respectively. Moreover, the space stem exhibits a non-uniform distributed temperature with a maximum value of several hundred Kelvin for tens of microseconds. Accordingly, a possible mechanism is proposed that the space stem is formed at the primary corona streamer boundary as a result of the propagation of a secondary ionization wave from the HV electrode and survives long enough (to finish the polarization) due to the fast gas heating and production of atomic oxygen.
Original languageEnglish
Article numbere2023GL102834
JournalGeophysical Research Letters
Issue number12
Publication statusE-pub ahead of print - Jun 2023


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