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Abstract Recent studies suggest that, despite its aurora‐like appearance, the picket fence may not be driven by magnetospheric particle precipitation but instead by local electric fields parallel to Earth's magnetic field. Here, we evaluate the parallel electric fields hypothesis by quantitatively comparing picket fence spectra with the emissions generated in a kinetic model driven by local parallel electric fields energizing ambient electrons in a realistic neutral atmosphere. We find that, at a typical picket fence altitude of 110 km, parallel electric fields between 40 and 70 Td (∼80–150 mV/m at 110 km) energize ambient electrons sufficiently so that, when they collide with neutrals, they reproduce the observed ratio of N₂first positive to atomic oxygen green line emissions, without producing first negative emissions. These findings establish a quantitative connection between ionospheric electrodynamics and observable picket fence emissions, offering verifiable targets for future models and experiments. 

Abstract We revisit the problem of photoionization of small admixtures of nitrogen and oxygen molecules in atmospheric pressure helium plasma originally formulated in the pioneering work of Naidis (2010J. Phys. D: Appl. Phys.43402001). The radiation trapping of resonance emission lines in atomic helium is quantified, and it is demonstrated that photoionization occurs due to radiative decay of the electronicAstate of helium molecules. The collisions and atomic precursors that populate the excitedAstate of the helium molecule are clearly identified. The Einstein probabilities for the transition from bound and quasi-bound rovibrational levels of theAstate to the continuum of the groundXstate are provided. A kinetic scheme for the production of the fast component of ultraviolet emissions in atmospheric pressure helium plasma is proposed. The photoionization of molecular oxygen and molecular nitrogen as impurities in 99.9% and 99.99% purity helium is studied. 

Abstract The first observation of possible transient luminous events (TLEs) on Jupiter was reported recently. Whereas initiation of elves on Jupiter has been theoretically studied before, the possibility of sprite streamer inception on Jupiter has not been investigated yet. Here we critically review the literature concerned with TLEs on Jupiter. Subsequently, we report on development of a numerical model for modeling of magnetized streamers in presence of Jupiter's strong magnetic field. The model utilizes the knowledge provided by recent observations of Jupiter's lightning and magnetic field by the Juno spacecraft. It is demonstrated that sprite streamer inception under realistic atmospheric conditions on Jupiter is possible. 

Abstract Terrestrial gamma‐ray flashes are linked to growth of long bidirectional lightning leader system consisting of positive and stepping negative leaders. The spatial extent of streamer zones of a typical lightning leader with tip potential exceeding several tens of megavolts is on the order of 10–100 m. The photoelectric absorption of bremsstrahlung radiation generated by avalanching relativistic runaway electrons occurs efficiently on the same spatial scales. The intense multiplication of these electrons is triggered when the size of the negative leader streamer zone crosses a threshold of approximately 100 m (for sea‐level air pressure conditions) allowing self‐replication of these avalanches due to the upstream relativistic electron seeds generated by the photoelectric absorption. The model results also highlight importance of electrode effects in interpretation of X‐ray emissions from centimeter to meter long laboratory discharges, in particular, a similar feedback effect produced by generation of runaway electrons from the cathode material. 

Abstract We present a theory based on the conventional two-term (i.e. Lorentzian) approximation to the exact solution of the Boltzmann equation in non-magnetized weakly ionized plasma to efficiently obtain the electron rate and transport coefficients in a magnetized plasma for an arbitrary magnitude and direction of applied electric field $\vec{E}$and magnetic field $\vec{B}$. The proposed transcendental method does not require the two-term solution of the Boltzmann equation in magnetized plasma, based on which the transport parameters vary as a function of the reduced electric field $E/N$, reduced electron cyclotron frequency ${\omega }_{\mathrm{c}\mathrm{e}}/N$, and angle $\mathrm{\angle }\vec{E},\vec{B}$between $\vec{E}$and $\vec{B}$vectors, whereNis the density of neutrals. Comparisons between the coefficients derived from BOLSIG+’s solution (obtained via the two-term expansion when $\vec{B}\ne 0$) and coefficients of the presented method are illustrated for air, a mixture of molecular hydrogen (H₂) and helium (He) representing the giant gas planets of the Solar System, and pure carbon dioxide (CO₂). The new approach may be used in the modeling of magnetized plasma encountered in the context of transient luminous events, e.g. sprite streamers in the atmosphere of Earth and Jupiter, in modeling the propagation of lightning’s electromagnetic pulses in Earth’s ionosphere, and in various laboratory and industrial applications of nonthermal plasmas. 

Abstract Electron detachment from O⁻is important for understanding of lightning‐induced upper atmospheric discharges. Contrary to previous studies, Rayment and Moruzzi (1978) (RM78) argue that the associative detachment reaction of O⁻with N₂proceeds with N₂in its ground state. Here, we analyze the experimental setup in RM78 and demonstrate that vibrationally excited N₂may have in fact contaminated the results, the theoretical approach in RM78 requires corrections, and the rate calculations provided in RM78 are inconsistent. As the vibrational temperature of N₂remains relatively low in the initial stages of gas discharges in air, i.e., streamer formation, we conclude that if in fact vibrationally excited N₂is required for the O⁻ + N₂→ N₂O + e reaction to proceed, the process will happen only in later stages of the discharge, e.g., during streamer to leader transition. Controlled experiments are required to reconcile the literature on the reaction of O⁻with ground state N₂.