Suprathermal Particles in XUV-Heated and Extended Exoplanetary Upper Atmospheres

Shematovich, V. I.; Бисикало, Д. В.; Ionov, D. E.

doi:10.1007/978-3-319-09749-7_6

Cited by 14 publications

(7 citation statements)

References 68 publications

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“…This procedure is analogous to a Monte Carlo algorithm for solving the stochastic kinetic equation. In the numerical realizations of the kinetic model the following recent developments in the theory and practice of DSMC method have been used (see, e.g., Shematovich 2004;Shematovich et al 2015): (i) an effective approximation of the major frequency, where the collision probability for the chosen pair is estimated from the maximum possible frequencies and is used in choosing the next transition; (ii) the multichannel nature of the selected reaction is taken into account for the transition to be realized; this means that the transition is treated as the simultaneous drawing of all possible (elastic, inelastic, and chemically reactive) channels for each one of which the corresponding weight is transferred to the total cross section of the collisional process, proportionally to the ratio of the partial cross section for the given channel; (iii) since the algorithmic steps of both introducing suprathermal particles (in accordance with the source functions) and drawing the collisional transitions are accompanied by the formation of new model particles, it is necessary to control the total number of model particles in the numerical model. An efficient method for this control is the so-called clustering of model particles, where groups of model particles with similar parameters are combined into a single particle with weighted parameters.…”

Section: Collision Times Between Molecular Species Become Longmentioning

confidence: 99%

Towards a Global Unified Model of Europa’s Tenuous Atmosphere

et al. 2018

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Despite the numerous modeling efforts of the past, our knowledge on the radiation-induced physical and chemical processes in Europa’s tenuous atmosphere and on the exchange of material between the moon’s surface and Jupiter’s magnetosphere remains limited. In lack of an adequate number of in situ observations, the existence of a wide variety of models based on different scenarios and considerations has resulted in a fragmentary understanding of the interactions of the magnetospheric ion population with both the moon’s icy surface and neutral gas envelope. Models show large discrepancy in the source and loss rates of the different constituents as well as in the determination of the spatial distribution of the atmosphere and its variation with time. The existence of several models based on very different approaches highlights the need of a detailed comparison among them with the final goal of developing a unified model of Europa’s tenuous atmosphere. The availability to the science community of such a model could be of particular interest in view of the planning of the future mission observations (e.g., ESA’s JUpiter ICy moons Explorer (JUICE) mission, and NASA’s Europa Clipper mission). We review the existing models of Europa’s tenuous atmosphere and discuss each of their derived characteristics of the neutral environment. We also discuss discrepancies among different models and the assumptions of the plasma environment in the vicinity of Europa. A summary of the existing observations of both the neutral and the plasma environments at Europa is also presented. The characteristics of a global unified model of the tenuous atmosphere are, then, discussed. Finally, we identify needed future experimental work in laboratories and propose some suitable observation strategies for upcoming missions

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Section: Collision Times Between Molecular Species Become Longmentioning

confidence: 99%

Towards a Global Unified Model of Europa’s Tenuous Atmosphere

et al. 2018

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“…mospheric loss on hydrogen-rich exoplanets (Shematovich et al, 2015). In our solar system, Pluto's atmosphere contains detectable CO and N 2 but lacks CO 2 (Steffl et al, 2020), whereas CO, CO 2 , and N 2 are the dominant constituents in the atmospheres of Mars and Venus, which have nearly identical UV spectra (Chaufray et al, 2012;Feldman et al, 2000;Gérard et al, 2017;Hubert et al, 2010).…”

mentioning

confidence: 86%

“…Carbon monoxide is the second most abundant molecule in interstellar space and is used as a tracer for presence of H 2 in star forming regions and molecular clouds (Ferlet et al., 2000; van Dishoeck & Black, 1986). Further, robust laboratory analysis of CO and CO 2 emission features may be an important asset in studying H 2 structures in exoplanetary upper atmospheres, the photolysis of which contributes significantly to atmospheric loss on hydrogen‐rich exoplanets (Shematovich et al., 2015). In our solar system, Pluto's atmosphere contains detectable CO and N 2 but lacks CO 2 (Steffl et al., 2020), whereas CO, CO 2 , and N 2 are the dominant constituents in the atmospheres of Mars and Venus, which have nearly identical UV spectra (Chaufray et al., 2012; Feldman et al., 2000; Gérard et al., 2017; Hubert et al., 2010).…”

Section: Introductionmentioning

confidence: 99%

Laboratory Study of the Cameron Bands, the First Negative Bands, and Fourth Positive Bands in the Middle Ultraviolet 180–280 nm by Electron Impact Upon CO

et al. 2021

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We have analyzed medium‐resolution (full width at half maximum, FWHM = 1.2 nm), Middle UltraViolet (MUV; 180–280 nm) laboratory emission spectra of carbon monoxide (CO) excited by electron impact at 15, 20, 40, 50, and 100 eV under single‐scattering conditions at 300 K. The MUV emission spectra at 100 eV contain the Cameron Bands (CB) CO(a 3Π → X 1Σ+), the fourth positive group (4PG) CO(A 1Π → X 1Σ+), and the first negative group (1NG) CO+(B 2Σ+ → X 2Σ) from direct excitation and cascading‐induced emission of an optically thin CO gas. We have determined vibrational intensities and emission cross sections for these systems, important for modeling UV observations of the atmospheres of Mars and Venus. We have also measured the CB “glow” profile about the electron beam of the long‐lived CO (a 3Π) state and determined its average metastable lifetime of 3 ± 1 ms. Optically allowed cascading from a host of triplet states has been found to be the dominant excitation process contributing to the CB emission cross section at 15 eV, most strongly by the d 3Δ and a' 3Σ+ electronic states. We normalized the CB emission cross section at 15 eV electron impact energy by multilinear regression (MLR) analysis to the blended 15 eV MUV spectrum over the spectral range of 180–280 nm, based on the 4PG emission cross section at 15 eV that we have previously measured (Ajello et al., 2019, https://doi.org/10.1029/2018ja026308). We find the CB total emission cross section at 15 eV to be 7.7 × 10−17 cm2.

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“…Two main hypotheses have been put forth to explain the existence of this envelope. The first is the expansion of the planetary atmosphere due to heating by radiation from the star [260,261], which gives rise to outflows of matter at rates of ∼10 10 g/s. The second is based on the mechanism of chargeexchange of ions in the stellar wind during collisions with atoms in the atmosphere [262].…”

Section: Uv Line Emission From the Atmospheres Of Exoplanetsmentioning

confidence: 99%

Scientific problems addressed by the Spektr-UV space project (world space Observatory—Ultraviolet)

et al. 2016

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Abstract-The article presents a review of scientific problems and methods of ultraviolet astronomy, focusing on perspective scientific problems (directions) whose solution requires UV space observatories. These include reionization and the history of star formation in the Universe, searches for dark baryonic matter, physical and chemical processes in the interstellar medium and protoplanetary disks, the physics of accretion and outflows in astrophysical objects, from Active Galactic Nuclei to close binary stars, stellar activity (for both low-mass and high-mass stars), and processes occurring in the atmospheres of both planets in the solar system and exoplanets. Technological progress in UV astronomy achieved in recent years is also considered. The well advanced, international, Russian-led Spektr-UV (World Space Observatory-Ultraviolet) project is described in more detail. This project is directed at creating a major space observatory operational in the ultraviolet (115-310 nm). This observatory will provide an effective, and possibly the only, powerful means of observing in this spectral range over the next ten years, and will be an powerful tool for resolving many topical scientific problems.

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Suprathermal Particles in XUV-Heated and Extended Exoplanetary Upper Atmospheres

Cited by 14 publications

References 68 publications

Towards a Global Unified Model of Europa’s Tenuous Atmosphere

Towards a Global Unified Model of Europa’s Tenuous Atmosphere

Laboratory Study of the Cameron Bands, the First Negative Bands, and Fourth Positive Bands in the Middle Ultraviolet 180–280 nm by Electron Impact Upon CO

Scientific problems addressed by the Spektr-UV space project (world space Observatory—Ultraviolet)

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