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1. Lightning Initiation From Fast Negative Breakdown is Led by Positive Polarity Dominated Streamers

   https://doi.org/10.1029/2020GL091553  

   Huang, Anjing; Cummer, Steven A.; Pu, Yunjiao (April 2021, Geophysical Research Letters)

   Abstract Evidence of positive polarity dominated streamers preceding fast negative breakdown (FNB) and of simultaneous positive and negative polarity streamer development in lightning initiation is reported. Observations of lightning initiation as FNB have remained a puzzle because simulations of lightning initiation have shown that negative streamers are not produced in virgin air without simultaneous positive streamers. Here, the authors observe positive streamer development forms first or at least simultaneously with negative streamers. Further evidence comes from observations of mixed fast breakdown (FB). The overall trajectory of the positive breakdown during such mixed events indicates that the positive streamers continuously propagate during the burst of strong negative breakdown. These observations indicate that even when negative streamers dominate the overall very high frequency (VHF) emissions, both positive and negative streamers are propagating simultaneously from the initiation point. These findings on the structure and dynamics of FB provide key new insight to our understanding of lightning initiation. 

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2. Fast negative breakdown in thunderstorms

   https://doi.org/10.1038/s41467-019-09621-z  

   Tilles, Julia N.; Liu, Ningyu; Stanley, Mark A.; Krehbiel, Paul R.; Rison, William; Stock, Michael G.; Dwyer, Joseph R.; Brown, Robert; Wilson, Jennifer (December 2019, Nature Communications)
3. Secondary Fast Breakdown in Narrow Bipolar Events

   https://doi.org/10.1029/2021GL097452  

   Li, Dongshuai; Luque, Alejandro; Gordillo‐Vázquez, F. J.; Silva, Caitano da; Krehbiel, Paul R.; Rachidi, Farhad; Rubinstein, Marcos (April 2022, Geophysical Research Letters)
4. Electrostatic Conditions That Produce Fast Breakdown in Thunderstorms

   https://doi.org/10.1029/2021JD034829  

   Attanasio, Alex; da Silva, Caitano; Krehbiel, Paul (September 2021, Journal of Geophysical Research: Atmospheres)

   Abstract Fast breakdown (FB), a breakdown process composed of systems of high‐velocity streamers, has been observed to precede lightning leader formation and play a critical role in lightning initiation. Vigorous FB events are responsible for the most powerful natural radio emissions on Earth, known as narrow bipolar events (NBEs). In this paper, an improved version of the Griffiths and Phelps (1976,https://doi.org/10.1029/jc081i021p03671) model of streamer breakdown is used alongside supervised machine learning techniques to probe the required electric fields and potentials inside thunderstorms to produce FB and NBEs. Our results show that the electrostatic conditions needed to produceFB observed in New Mexico at 9 km altitude andFB in Florida at 14 km altitude are about the same, each requiring about 100 MV potential difference to propagate 500 m. Additionally, the model illustrates how electric field enhancement ahead of propagating FB can initiate rebounding FB of the opposite polarity. 

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5. False negative and false positive free nanopore fabrication via adaptive learning of the controlled dielectric breakdown

   Rosha, Kamyar; Tang, Zifan; Guan, Weihua (May 2019, Transducer 2019)

   We investigate the current transport characteristics in the electrolyte-dielectric-electrolyte structure commonly used in the in-situ controlled breakdown (CBD) fabrication of solid-state nanopores. It is found that the stochastic breakdown process could lead to fidelity issues of false positives (an incorrect indication of a true nanopore formation) and false negatives (inability to detect initial nanopore formation). Robust and deterministic detection of initial physical breakdown to alleviate false positives and false negatives is critical for precise nanopore size control. To this end, we report a high fidelity moving Z-Score method based CBD fabrication of solid-state nanopore. We demonstrate 100% success rate of realizing the initial nanopore conductance of 3±1 nS (corresponds to the size of 1.7±0.6 nm) regardless of the dielectric membrane characteristics. Our study also elucidates the Joule heating is the dominant mechanism for electric field-based nanopore enlargement. Single DNA molecule sensing using nanopores fabricated by this method was successfully demonstrated. We anticipate the moving Z-Score based CBD method could enable broader access to the solid state nanopore-based single molecule analysis. 

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