Yunjiao Pu

Journal Article Geophysical Research Letters · October 28, 2025 We initiated high-frequency (HF, 3–30 MHz) lightning observations to remotely study lightning processes using skywave propagation. HF lightning skywaves were detected at distances up to 3,300 km (potentially farther) during both day and night, with over 64 ... Full text Cite

An Efficient Lightning Classifier Using a Self-Supervised Learning Neural Network

Journal Article Geophysical Research Letters · June 28, 2025 The automatic classification of lightning discharge processes is a critical challenge in both lightning physics research and protection. Despite recent advancements in artificial intelligence-based classification models, rely on supervised learning, which ... Full text Cite

Continuous Initial Breakdown Development of In-Cloud Lightning Flashes

Journal Article Journal of Geophysical Research Atmospheres · October 28, 2024 Using a 30–250 MHz VHF interferometer, we observed a previously unreported mode of initial lightning development inside thunderclouds. This mode is defined by continuous VHF radiation spanning several km within the first few milliseconds of lightning initi ... Full text Cite

Evidence of a New Population of Weak Terrestrial Gamma-Ray Flashes Observed From Aircraft Altitude

Journal Article Geophysical Research Letters · September 16, 2024 Terrestrial Gamma-ray Flashes (TGFs) are ten-to-hundreds of microsecond bursts of gamma-rays produced when electrons in strong electric fields in thunderclouds are accelerated to relativistic energies. Space instruments have observed TGFs with source photo ... Full text Cite

Imaging Step Formation in In-Cloud Lightning Initial Development With VHF Interferometry

Journal Article Geophysical Research Letters · January 16, 2024 We investigate sequential processes underlying the initial development of in-cloud lightning flashes in the form of initial breakdown pulses (IBPs) between 7.4 and 9.0 km altitudes, using a 30–250 MHz VHF interferometer. When resolved, IBPs exhibit typical ... Full text Cite

Determining a Lower Limit of Luminosity for the First Satellite Observation of a Reverse Beam Terrestrial Gamma Ray Flash Associated With a Cloud to Ground Lightning Leader

Journal Article Journal of Geophysical Research Atmospheres · September 27, 2023 We provide an updated analysis of the gamma ray signature of a terrestrial gamma ray flash (TGF) detected by the Fermi Gamma ray Burst Monitor first reported by Pu et al. (2020, https://doi.org/10.1029/2020GL089427). A TGF produced 3 ms prior to a negative ... Full text Cite

Unsupervised Clustering and Supervised Machine Learning for Lightning Classification: Application to Identifying EIPs for Ground-Based TGF Detection

Journal Article Journal of Geophysical Research Atmospheres · May 16, 2023 We developed a framework merging unsupervised and supervised machine learning to classify lightning radio signals, and applied it to the possible detection of terrestrial gamma-ray flashes (TGFs). Recent studies have established a tight connection between ... Full text Cite

Transition in Optical and Radio Features During the Early Development of Negative Intracloud Leader

Journal Article Geophysical Research Letters · November 28, 2022 What happens when the upward in-cloud (IC) breakdown transitions into horizontally expanding extension? Optical observations of this transition in IC lightning have not previously been reported. We identify the radio and optical signatures of this transiti ... Full text Cite

Quantification of Electric Fields in Fast Breakdown During Lightning Initiation From VHF-UHF Power Spectra

Journal Article Geophysical Research Letters · March 16, 2022 This work applies a new remote sensing approach to indirectly probe the electric fields in the discharge region of fast breakdown (FB) processes during lightning initiation. A VHF-UHF broadband (1–750 MHz) measurement system is used to record the radiation ... Full text Cite

Three dimensional acoustic tweezers with vortex streaming

Journal Article Communications Physics · December 1, 2021 Acoustic tweezers use ultrasound for contact-free manipulation of particles from millimeter to sub-micrometer scale. Particle trapping is usually associated with either radiation forces or acoustic streaming fields. Acoustic tweezers based on single-beam f ... Full text Cite

VHF Radio Spectrum of a Positive Leader and Implications for Electric Fields

Journal Article Geophysical Research Letters · June 16, 2021 Electric fields associated with a developing natural lightning leader are difficult to measure. This work demonstrates a new approach to indirectly probing the electric fields in the streamer zone of a lightning leader. Using a 10–250 MHz broadband lightni ... Full text Cite

Simultaneous Observations of EIP, TGF, Elve, and Optical Lightning

Journal Article Journal of Geophysical Research Atmospheres · June 1, 2021 On February 8, 2019, the Atmosphere-Space Interaction Monitor observed a terrestrial gamma-ray flash (TGF) and an Elve from a positive intracloud (+IC) lightning during the initial breakdown stage of a lightning flash north east of Puerto Rico. A second El ... Full text Cite

On the Terrestrial Gamma-Ray Flashes Preceding Narrow Bipolar Events

Journal Article Geophysical Research Letters · April 28, 2021 Narrow bipolar events (NBEs) are occasionally reported to occur within a few ms after Terrestrial Gamma-ray Flashes (TGFs), while the formation mechanism remains mysterious partially due to the lack of sufficient observations. Here, nine more TGFs of this ... Full text Cite

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

Journal Article Geophysical Research Letters · April 28, 2021 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 ... Full text Cite

A Satellite-Detected Terrestrial Gamma Ray Flash Produced by a Cloud-to-Ground Lightning Leader

Journal Article Geophysical Research Letters · August 16, 2020 We report measurements of a terrestrial gamma ray flash (TGF) detected by the Fermi Gamma-ray Burst Monitor that was produced during a negative cloud-to-ground (CG) lightning leader. This is the first report of a downward directed TGF occurring during a CG ... Full text Cite

Characteristics of Impulsive Currents Superimposing on Continuous/Continuing Current of Rocket-Triggered Lightning

Journal Article IEEE Transactions on Electromagnetic Compatibility · August 1, 2020 Characteristics and mechanism of initial continuous current (ICC) pulses and M components in rocket-triggered lightning were investigated in detailed. The geometric mean current peak, risetime from 10% to 90% peak, half-peak width, and charge transfer of M ... Full text Cite

Needles and Lightning Leader Dynamics Imaged with 100–200 MHz Broadband VHF Interferometry

Journal Article Geophysical Research Letters · November 28, 2019 A new short-baseline VHF interferometer with 200 MHz bandwidth images lightning with significantly higher spatial resolution than our previous system with a 60 MHz maximum frequency. Needles (Hare et al., 2019, https://doi.org/10.1038/s41586-019-1086-6), n ... Full text Cite

Low Frequency Radio Pulses Produced by Terrestrial Gamma-Ray Flashes

Journal Article Geophysical Research Letters · June 28, 2019 Do terrestrial gamma-ray flashes (TGFs) produce their own radio signatures? To explore this question, we analyze TGF data from the Fermi Gamma-ray Burst Monitor, independent lightning geolocation data from the National Lightning Detection Network, and low- ... Full text Cite

Broadband Characteristics of Chaotic Pulse Trains Associated With Sequential Dart Leaders in a Rocket-Triggered Lightning Flash

Journal Article Journal of Geophysical Research Atmospheres · April 16, 2019 Based on simultaneous measurements of fast E-field change, very high frequency radiation and channel mapping, channel base current, and high-speed video, the characteristics of chaotic pulse trains (CPTs) during propagation of dart leaders in a rocket-trig ... Full text Cite

Propagation of positive, negative, and recoil leaders in upward lightning flashes

Journal Article Earth and Planetary Physics · March 1, 2019 Leader propagation is a fundamental issue in lightning physics. The propagation characteristics of positive leaders and negative leaders are summarized and compared based on data from high-speed camera and electromagnetic field in rocket-triggered lightnin ... Full text Cite

Comparison between upward positive and negative leaders of lightning in their initial stage∗

Conference 34th International Conference on Lightning Protection Iclp 2018 · October 23, 2018 The initial development of upward positive and negative leader is studied and compared based on the simultaneous data from high-speed video camera, channel base current, and electromagnetic field changes documented in the rocket-triggered lightning and tow ... Full text Cite

Upward negative leaders in positive triggered lightning: Stepping and branching in the initial stage

Journal Article Geophysical Research Letters · July 16, 2017 By conducting comprehensive observation on the rarely triggered positive lightning flashes, two cases of upward negative leaders were quantitatively investigated with simultaneous data of current, optical, and electromagnetic field changes at fine time res ... Full text Cite

Bidirectional leader development in a pre-existing channel as observed in rocket-triggered lightning flashes

Journal Article Journal of Geophysical Research · January 1, 2017 Two cases of bidirectional leader, starting almost immediately below a decaying dart or dart-stepped leader which terminated before reaching the ground, were identified, for the first time, in rocket-triggered lightning flashes based on high-speed video, e ... Full text Cite

High-speed video observation of stepwise propagation of a natural upward positive leader

Journal Article Journal of Geophysical Research · December 27, 2016 Using a high-speed video camera operated at 150,000 frames per second, we have documented the upward propagation of an initial positive leader from a 325m meteorological tower in Beijing. The stepwise development of the upward positive leader was clearly r ... Full text Cite