A general framework for photoionization rate calculations in a constant pressure gaseous medium is introduced. The formulation includes the number of photons emitted per unit volume per unit time per unit wavelength due to a radiating source, photobasorption cross sections and density of species comprising the medium, and the photoionization probability (i.e. photoionization yield) of the species being photoionized. We derive a standard integral representation of the photoionization problem that may be readily converted to a set of Helmholtz differential equations for efficient calculation of the photoionization rate. The model is applied to the photoionization problem in air in which P b u 1 , ¢ S + b u 1 , P c u 3 1 , P o u 3 1 , ¢ S + c u 4 1 ( ), derived from the classic photoionization model of Zheleznyak et al (1982) and more recent experimental data on photoionization in air.

The first observation of possible transient luminous events (TLEs) on Jupiter was recently reported by Giles et al. (2020). This is a finding that resembles the serendipitous capture of Earth's TLEs on camera three decades ago (Franz et al., 1990). Specifically, the ultraviolet spectrograph (UVS) aboard the Juno spacecraft has recorded 11 optical signals during the first 4 years of the mission that may have originated from TLEs on Jupiter. Light curves for 10 of the flashes show a mean decay time of ∼1.4 ms while the remaining flash has a noticeably shorter duration (i.e., 0.1 ms), which possibly may be because Juno's UVS was triggered immediately before the photodetector moved off the flash. Additional properties of the detected flashes and the observation geometry may be found in Giles et al. (2020, Table 1). 2020) use a model of radiative transfer in Jupiter's atmosphere to locate the altitude of flashes. It is concluded that the best fit to the recorded spectrum of flashes is obtained for a source altitude of ∼258 km above the 1-bar level (i.e., ∼10 μbar pressure). Giles et al. ( 2020) emphasize that UV observations cannot probe altitudes below that corresponding to 100 mbar. As such, the UV signature of lightning, which is generally thought to occur at ∼5 bar and even the recently observed "shallow lightning" (Becker et al., 2020) that occurs at pressures higher than 1.4 bar will be absent from Juno UVS observations (e.g., Moses et al., 2005, Figure 8). It is therefore clear that Giles et al. (2020) did not observe typical lightning discharges. Giles et al. (Previous observations of Jupiter lightning were limited by camera sensitivity, distance from Jupiter and long exposures. This contributed to the exclusive detection of Jupiter lightning with optical energies comparable to terrestrial superbolts (e.g., Turman, 1977) (i.e., ∼10 9 J). Juno's observations of Jupiter, however, has led to the conclusion that Jupiter lightning predominantly consists of flashes with optical energies similar to typical terrestrial energies (i.e., 10 5 -10 8 J) (Becker et al., 2020, Figure 2). Kolmašová et al. (2018) report a much higher lightning frequency, which is comparable to the frequency of lightning on Earth, and Becker et al. (2020) report an increase in the flash rate from ∼4 × 10 −3 to ∼6.1 × 10 −2 flashes per square kilometer per year with several flashes

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 N2 proceeds with N2 in its ground state. Here, we analyze the experimental setup in RM78 and demonstrate that vibrationally excited N2 may 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 N2 remains relatively low in the initial stages of gas discharges in air, i.e., streamer formation, we conclude that if in fact vibrationally excited N2 is 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.

Terrestrial gamma ray flashes (TGFs) (Fishman et al., 1994) represent a spectacular naturally occurring high energy phenomenon in the Earth's atmosphere. These events contain photons with several tens of mega electron-volt energies and likely involve large quantities of energetic electrons, sharing the same physical origin as X-rays generated by laboratory sparks (Stankevich & Kalinin, 1967) or originating from stepping lightning leaders (Moore et al., 2001). Dwyer et al. (2012) provide a review of principal physical processes and experimental findings on TGFs and related phenomena.It has been discovered by Dwyer (2003) that in order to explain observed intensities of TGFs a feedback mechanism should be involved in these events when an avalanche of relativistic electrons launches positrons and X-rays backwards at its origin to provide additional seeding and replenishment of the avalanche. Dwyer (2003) noted a physical analogy between this relativistic feedback mechanism and feedback mechanisms in conventional Townsend discharges involving positive ions and optical photons. The self-consistent modeling of a large scale streamer (domain size ∼5 km) and related space charge effects driven by the relativistic feedback discharges in air around 11-12 km altitudes have been reported by Dwyer (2012) and Liu and Dwyer (2013). It has been

A framework is developed to model photoionization of metals deposited in the lower ionosphere as a result of meteoric ablation and photodetachment of electrons from negative ions of the Earth's ionosphere due to sources of emission other than solar radiation. A wide range of the electromagnetic spectrum including cases of negligible, moderate, and significant absorption of radiation is considered. We limit our scope to the radiation transport through lower ionospheric regions, in case when molecular oxygen, O2, is considered as the main absorber of radiation as photoabsorption due to ozone is only effective at stratospheric altitudes and molecular nitrogen, N2, is transparent to radiation with wavelengths longer than ∼100 nm. We model photon transport in an exponential atmosphere and derive efficient differential representations of the problem in case of negligible photoabsorption and constant pressure approximations. Photoabsorption asymmetry in the atmosphere is demonstrated in case of photons with absorption scales comparable to the scale height of the atmosphere. The application of the model to photoionization in the lower ionosphere is demonstrated by considering photoionization of meteoric species due to photons of the Lyman‐Birge‐Hopfield (LBH) band system of N2 observed in the aurora and in the lightning‐induced transient luminous events. Furthermore, we model detachment of electrons from negative ions of the ionosphere due to the first positive and the second positive band systems of N2, and the first negative band system of N 2+, also observed in the sources mentioned above.