A full time-dependent kinetic study is presented for the main microscopic collisional and radiative processes underlying the optical flashes associated with an impulsive (τ = 5 µs) discharge in the form of a single sprite streamer passing through an air region of the mesosphere at three different altitudes (63, 68 and 78 km). The kinetic formalism developed includes the coupling of the rate equations of each of the different species considered (electrons, ions, atoms and molecules) with the Boltzmann transport equation so that, in this way, all the kinetics is self-consistent, although, in the present approach, the electrodynamics (no Poisson equation is considered) is not coupled. The chemical model set up for air plasmas includes more than 75 species and almost 500 reactions. In addition, a complete set of reactions (more than 110) has been considered to take into account the possible impact of including H2O (humid chemistry) in the generated air plasmas. This study also considers the vibrational kinetics of N2 and CO2 and explicitly evaluates the optical emissions associated with a number of excited states of N2, O2, O in the visible, CO2 in the infrared (IR) and ultraviolet (UV) emissions of sprite streamers due to the N2 Lyman–Birge–Hopfield (LBH) and the NO-γ band systems. All the calculations are conducted for midnight conditions in mid-latitude regions (+38°N) and 0° longitude, using as initial values for the neutral species those provided by the latest version of the Whole Atmosphere Community Climate Model (WACCM). According to our calculations, the impact of 4 ppm of H2O is only slightly visible in at 68 and 78 km while it strongly affects the behaviour of the anion at all the altitudes investigated. The local enhancement of NOx predicted by the present model varies with the altitude. At 68 km, the concentrations of NO and NO2 increase by about one order of magnitude while that of NO3 exhibits a remarkable growth of up to almost three orders of magnitude. The variation of the O3 density predicted by the model in the sprite streamer head is negligible in all the altitudes investigated. The analysis of the time dependence of the electron distribution function (EDF) in the sprite plasma during the pulse reveals that the EDF transient is quite fast, reaching its ‘steady’ values during the pulse in less than 100 ns (much shorter than streamer head lifetimes). In addition, the calculated EDF during the pulse and in the afterglow is far from being Maxwellian, especially for energetic electrons (with ε > 30 eV). Finally, the evaluation of the mid-latitude nighttime electrical conductivity of air plasmas under the influence of a single sprite event reveals an increase of up to four orders of magnitude (at 68 km) above its measured background level of at an altitude of ∼70 km. This sudden increase in the electrical conductivity lasts for 100 ms (at 68 km), being shorter (∼1 ms) and longer (1 s) at 63 km and 78 km, respectively. The total power delivered by the streamer head of a single sprite event has been...

While narrow bipolar events (NBEs) could be related with lightning initiation, their intrinsic physics remains in question. Here we report on optical measurements by the Atmosphere‐Space Interactions Monitor (ASIM) on the International Space Station (ISS) of blue flashes associated with NBEs. They are observed in a narrow blue band centered at 337 nm, with no simultaneous activity at 777.4 nm, considered a strong lightning emission line. From radio waves measured from the ground, we find that 7 of 10 single‐pulse blue events can be identified as positive NBEs. The source altitudes estimated from optical and radio signals agree and indicate that the sources of the blue flashes are located between ∼8.5 and ∼14 km, in a cloud reaching 14–15 km altitude. The observations suggest that single‐pulse blue flashes are from cold ionization waves, so‐called streamers, and that positive NBEs are corona discharges formed by many streamers.

The chemical composition of a low-pressure hydrogen dc plasma produced in a hollow cathode discharge has been measured and modeled. The concentrations of H atoms and of H + , H 2 + and H 3 + ions were determined with a combination of optical spectroscopic and mass spectrometric techniques, over the range of pressures (p ∼0.008-0.2 mbar) investigated. The results were rationalized with the help of a zero-order kinetic model. A comparatively high fraction (∼0.1 ( 0.05) of H atoms, indicative of a relatively small wall recombination, was observed. Low ionization degrees (<10 -4 ) were obtained in all cases. In general, the ionic composition of the plasma was found to be dominated by H 3 + , except at the lowest pressures, where H 2 + was the major ion. The key physicochemical processes determining the plasma composition were identified from the comparison of experimental and model results, and are discussed in the paper.

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[1] The vibrational kinetics of air plasmas produced by the presence of sprites in the mesosphere of the Earth is studied in detail. The present model solves the coupled electron Boltzmann equation and rate equations for electrons, neutrals (ground and excited), and ions. Special attention is paid to the vibrational kinetics of N 2 (X 1 S g + ) and to that of the N 2 triplet states (A 3 S u + , B 3 P g , C 3 P u , W 3 D u , and B′ 3 S u + ). The results presented are for an altitude of 78 km over sea level where the model-predicted vibrational distribution function (VDF) of N 2 (B 3 P g ) is in agreement with available VDF derived from sprite spectra (640-820 nm) obtained using spectrographs coupled to high-speed video cameras (300 frames per second (fps)). In addition, the model predictions indicate that the sprite plasma VDFs of N 2 (B 3 P g ) and N 2 (C 3 P u ) are almost in thermal equilibrium and exhibit a maximum at v = 0 followed by lower values for v = 1 and v = 2. Finally, it is also predicted that the N 2 (B 3 P g ) and N 2 (C 3 P u ) VDFs recorded with very high speed video cameras (up to 10000 fps) should not differ much from the N 2 (B 3 P g ) and N 2 (C 3 P u ) VDFs obtained with cameras working at lower speeds (30 and 300 fps).

The initial stages of transient luminous events (TLEs) occurring in the upper atmosphere of the Earth are, in a certain pressure range, controlled by the streamer mechanism. This paper presents the results of the first laboratory experiments to study the TLE streamer phenomena under conditions close to those of the upper atmosphere. Spectrally and highly spatiotemporally resolved emissions originating from radiative states ( )(second positive system) and(first negative system) have been recorded from the positive streamer discharge. Periodic ionizing events were generated in a barrier discharge arrangement at a pressure of 4 torr of synthetic air, i.e. simulating the pressure conditions at altitudes of ≃37 km. Employing Abel inversion on the radially scanned streamer emission and a 2D fitting procedure, access was obtained to the local spectral signatures within the over 10 6 m s −1 fast propagating streamers. The reduced electric field strength distribution within the streamer head was determined from the ratio of the / + N N 2 2 band intensities with peak values up to 500 Td and overall duration of about 10 ns. The 2D profiles of the streamer head electric fields were used as an experimentally obtained input for kinetic simulations of the streamer-induced air plasma chemistry. The radial and temporal computed distribution of the ground vibrational levels of the radiative states involved in the radiative transitions analyzed (337.1 nm and 391.5 nm), atomic oxygen, nitrogen, nitric oxide and ozone concentrations are vizualized and discussed in comparison with available models of the streamer phase of Blue Jet discharges in the stratosphere.

Narrow Bipolar Events (NBEs) are powerful radio emissions from thunderstorms, which have been recently associated with blue optical flashes on cloud tops and attributed to extensive streamer electrical discharges named fast breakdown. Combining data obtained from a thunderstorm over South China by the space‐based Atmosphere Space Interactions Monitor, the Vaisala GLD360 global lightning network and very low frequency/low frequency radio detectors, here we report and analyze for the first time the optical emissions of blue luminous events associated with negative NBEs and located at the top edge of a thundercloud. These emissions are weakly affected by scattering from cloud droplets, allowing us to estimate the source extension and optical energy involved in the process. The optical energy in the 337‐nm band emitted by fast breakdown is about 104 J, which involves around 109 streamer initiation events.

Analytical expressions for the rotational-vibrational energy levels of diatomic molecules represented by the Tietz-Hua rotating oscillator are derived using the Hamilton-Jacoby theory and the Bohr-Sommerfeld quantization rule. In molecules with moderate and large values of rotational and vibrational quantum numbers, the levels are in much better agreement with the results of numerical calculations than the energies obtained from the common model of the rotating Morse oscillator.