Atomic H is a direct tracer of water loss at Mars. The recent discovery of annual enhancements in its escape rate near perihelion, in excess of the previously established theory, indicates that Mars has lost substantial amounts of water... more
Atomic H is a direct tracer of water loss at Mars. The recent discovery of annual enhancements in its escape rate near perihelion, in excess of the previously established theory, indicates that Mars has lost substantial amounts of water to space. However, these loss rates are often estimated assuming thermal properties for the exospheric H atoms and are therefore a lower limit. Past analyses of spacecraft observations delivered indirect evidence for the existence of an energetic non‐thermal H population without a clear detection. Here, we present the unambiguous observational signature of non‐thermal H at Mars, consistent with solar wind charge exchange as the primary driver for its production. The calculated non‐thermal escape rates are as high as ∼26% of the thermal rate near aphelion and solar minima. An active Sun would increase the present‐day escape rate and a younger energetic Sun likely contributed toward the significant historic loss of water from Mars.
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ABSTRACT An overview of results obtained in the field of planetary atmosphere studies in Russia in 2007-2010 prepared by the Commission on Planetary Atmospheres of the National Geophysical Committee for the National Report on Meteorology... more
ABSTRACT An overview of results obtained in the field of planetary atmosphere studies in Russia in 2007-2010 prepared by the Commission on Planetary Atmospheres of the National Geophysical Committee for the National Report on Meteorology and Atmospheric Sciences to the XXV General Assembly of the International Union of Geodesy and Geophysics (Melbourne, 28 June-7 July 2011) [1, 2] is presented.
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Research Interests: Materials Science, Hydrogen, Mars, Magnetic field, Aurora, and 3 morePrecipitation, Geophysical, and Proton
The non-thermal atmospheric losses due to the contribution of the exothermic photochemistry to the formation of a fractionof suprathermal atomic hydrogen in the H 2 → H transition region were studied and compared for two exoplanets of... more
The non-thermal atmospheric losses due to the contribution of the exothermic photochemistry to the formation of a fractionof suprathermal atomic hydrogen in the H 2 → H transition region were studied and compared for two exoplanets of differenttypes and different parent star. Exoplanet GJ 436b is a warm neptune orbiting the red dwarf GJ 436. The calculated non-thermal fluxes due to the exothermic photochemistry for both exoplanets were found in the range (3.0 − 3.5) × 10 12 cm −2s −1 for a moderate level of stellar activity in UV radiation.
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HST transit observations in the near-UV performed in 2009 made WASP-12b one of the most "mysterious" exoplanets; the system presents an early-ingress, which can be explained by the presence of optically thick matter located... more
HST transit observations in the near-UV performed in 2009 made WASP-12b one of the most "mysterious" exoplanets; the system presents an early-ingress, which can be explained by the presence of optically thick matter located ahead of the planet at a distance of 4-5 planet radii. This work follows previous attempts to explain this asymmetry with an exospheric outflow or a bow shock, induced by a planetary magnetic field, and provides a numerical solution of the early-ingress, though we did not perform any radiative transfer calculation. We performed pure 3D gas dynamic simulations of the plasma interaction between WASP-12b and its host star, and describe the flow pattern in the system. In particular, we show that the overfilling of the planet's Roche lobe leads to a noticeable outflow from the upper atmosphere in the direction of the L1 and L2 points. Due to the conservation of the angular momentum, the flow to the L1 point is deflected in the direction of the planet'...
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Magnetometer measurements now suggest that all three large icy moons of Jupiter may have an underground ocean [1]. The morphology and the color variations of Europa’s surface are suggestive that ma-terials from its ocean may have modified... more
Magnetometer measurements now suggest that all three large icy moons of Jupiter may have an underground ocean [1]. The morphology and the color variations of Europa’s surface are suggestive that ma-terials from its ocean may have modified the surface in geologically recent times. In addition, an evaporite has been suggested to be present on Europa's surface that may have come from a subsurface ocean [2], but this has been questioned [3,4]. There is evidence, however, for the presence of organics on some of these satellites [5,6]. Hubble Space Telescope (HST) and Galileo Or-biter observations have identified atmospheric products of irradiation processes, O2 on Europa and Ganymede, and CO2 on Callisto. The most recent HST observa-tions [7] show potential correlations of atmospheric
Abstract. It is suggested that the incorporation of HCN in Titan’s atmospheric haze may be an important process affecting the HCN profile and the C/N ratio in Titan’s haze. By introducing a loss to the haze term for HCN (i.e. a production... more
Abstract. It is suggested that the incorporation of HCN in Titan’s atmospheric haze may be an important process affecting the HCN profile and the C/N ratio in Titan’s haze. By introducing a loss to the haze term for HCN (i.e. a production term of “poly-HCN”) in the photochemical model of Lara et al. (1996), we have improved the model’s ability to simultaneously reproduce the observed HCN and C2 hydrocarbon profiles in Titan’s lower stratosphere. The loss rate of HCN by this process may be a few times 10 8 cm −2 s −1. The calculated C/N ratio in the haze, assuming that the haze is primarily produced from C6H2,C8H2 and “poly–HCN”, is approximately equal to 2, in agreement with the composition of laboratory tholin analogues. Key words: molecular processes – planets and satellites: individual:
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The Submillimeter Wave Instrument (SWI) is part of the payload of ESA's L1 mission JUICE (JUpiter ICy moons Explorer). It sounds the middle atmosphere of Jupiter and the exospheres and surfaces of the Galilean satellites with a 290 mm... more
The Submillimeter Wave Instrument (SWI) is part of the payload of ESA's L1 mission JUICE (JUpiter ICy moons Explorer). It sounds the middle atmosphere of Jupiter and the exospheres and surfaces of the Galilean satellites with a 290 mm telescope, movable in azimuth and elevation using two heterodyne spectrometers covering the frequency ranges of 530 to 625 GHz and 1080 to 1275 GHz. The heterodyne receivers with tunable solid-state local oscillators and subharmonically pumped mixers are passively cooled. The performance of the receivers has been steadily improved during the last 2-3 years. Presently the receiver temperatures are about 1100 and 2000 K DSB (600 and 1200 GHz respectively). The intermediate frequency output of 3.5 to 8.5 GHz is analyzed by two real-time spectrometer backends consisting of broadband autocorrelators, high resolution multi-channel Chirp Transform Spectrometers and continuum channels. In order to fulfill the very stringent mass limitations of the JUICE pa...
The 41st annual student scientific conference "Physics of Space" aims to overcome the gap between modern scientific research and basic education in astronomy. The main purpose of the conference is to introduce the students to... more
The 41st annual student scientific conference "Physics of Space" aims to overcome the gap between modern scientific research and basic education in astronomy. The main purpose of the conference is to introduce the students to modern problems and directions of scientific research. The working languages of the conference are Russian and English.
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We have performed numerical simulations of the interaction between a “hot Jupiter” planet and gas of the stellar wind using a numerical code developed for investigations of binary stars. With this code, we have modeled the structure of... more
We have performed numerical simulations of the interaction between a “hot Jupiter” planet and gas of the stellar wind using a numerical code developed for investigations of binary stars. With this code, we have modeled the structure of the gaseous flow in the system HD 209458. The results have been used to explain observations of this system performed with the COS instrument on-board the HST.
We have applied time-dependent two-component hydrodynamics/radiative transfer calculations to investigate the structure, dynamics and spectral energy distribution of dusty circumstellar shells during post-AGB phase of evolution. Detailed... more
We have applied time-dependent two-component hydrodynamics/radiative transfer calculations to investigate the structure, dynamics and spectral energy distribution of dusty circumstellar shells during post-AGB phase of evolution. Detailed computations performed for the AGB phase of evolution (Steffen et al. 1998), based on the stellar evolutionary calculations with a prescribed AGB mass loss rate, have been used as initial models for the presented work. We have investigated the influence of the moment when the strength of heavy AGB wind has been reduced (end of the AGB) and the influence of the post-AGB mass loss rates on the spectral behaviour of the computed models. Comparison with observations compiled from the literature allows us to put constraints on these two fundamental parameters and on the whole transition phase between AGB and planetary nebulae. In the next step, computed density, velocity and temperature structure of the envelope, have been used to investigate the excitat...
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ABSTRACT The processes of kinetics and transport of hot oxygen and hydrogen atoms in the transition (from the thermosphere to the exosphere) region of the upper Martian atmosphere are studied. The reaction of dissociative recombination of... more
ABSTRACT The processes of kinetics and transport of hot oxygen and hydrogen atoms in the transition (from the thermosphere to the exosphere) region of the upper Martian atmosphere are studied. The reaction of dissociative recombination of the principal ionospheric ion O{2/+} with thermal electrons in the ionosphere of Mars served as the source of hot oxygen atoms. The process of momentum and energy transfer in elastic collisions between hot oxygen atoms and atmospheric hydrogen atoms with thermal energies was regarded as the source of hot hydrogen atoms. The kinetic energy distribution functions are determined for suprathermal oxygen and hydrogen atoms. It is shown that the exosphere is populated with a significant number of suprathermal oxygen atoms with kinetic energies ranging up to the escape energy of 2 eV (i.e., the hot oxygen Martian corona is formed). The transfer of energy from hot oxygen atoms to thermal hydrogen atoms creates an additional nonthermal flux of atomic hydrogen escaping from the Martian atmosphere.
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Based on HST and Voyager observations, the inner Saturnian system is populated by neutral OH and H clouds. These are thought to be residuals of the chemistry of H2O ejected from surfaces of E-ring grains and satellites by UV photons,... more
Based on HST and Voyager observations, the inner Saturnian system is populated by neutral OH and H clouds. These are thought to be residuals of the chemistry of H2O ejected from surfaces of E-ring grains and satellites by UV photons, ions, electrons, and micrometeorites(Jurac et al. Icarus Vol 149, pp 384-396, 2001). The model of H2O chemistry presented here includes the H2O sources, solar UV and magnetospheric electron impacts, losses due to interaction with the Saturnian magnetospheric plasma, and a chemistry network with ion-molecular, neutral-neutral, and molecular ion dissociative recombination reactions. Rates for the chemistry network were updated where possible. The neutral-neutral chemistry, in spite of the energy barriers, was taken into account. That is, although the ambient gas temperature in the inner Saturnian system is low, nonthermal (hot) products of H2O dissociation can result in endothermic reactions such as Hh+ H2O -> OH + H2. This model will allow us to consi...
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Sputtering and radiolysis of the icy satellite surfaces are important sources of neutrals in the Jovian and Saturnian systems [1,2]. We have presented collisional Monte Carlo models of surface-bounded exospheres of the icy satellites in... more
Sputtering and radiolysis of the icy satellite surfaces are important sources of neutrals in the Jovian and Saturnian systems [1,2]. We have presented collisional Monte Carlo models of surface-bounded exospheres of the icy satellites in which the sublimation and sputtering sources of H2O molecules and their molecular fragments are accounted for as well as the physical and chemical exchange at the atmosphere-icy surface interface. Products of radiolytic interactions by more penetrating electrons and ions in the volume ice are incorporated into the sublimation source of escaping volatiles. The very tenuous hydrogen and oxygen exospheres originate from a balance between sources from irradiation of the icy satellite surface by solar UV photons and magnetospheric plasma and losses from pick-up ionization and ejection following dissociation or collisions with the low energy plasma ions. The surface-bounded exospheres of the icy satellites are characterized by the hot coronas formed due to...
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Shematovich et al. recently showed plasma induced sputtering in Titan's atmosphere is a source of neutral nitrogen in Saturn's magnetosphere comparable to the photo-dissociation source. These sources form a toroidal nitrogen... more
Shematovich et al. recently showed plasma induced sputtering in Titan's atmosphere is a source of neutral nitrogen in Saturn's magnetosphere comparable to the photo-dissociation source. These sources form a toroidal nitrogen cloud roughly centered at Titan's orbital radius but gravitationally bound to Saturn. Once ionized, these particles contribute to Saturn's plasma. When Titan is inside Saturn's magnetopause, newly formed ions can diffuse inward becoming inner magnetospheric energetic nitrogen where they can sputter and be implanted into icy satellite surfaces. Our 3-D simulation produces the first consistent Titan generated N and N2 neutral clouds; solar UV radiation and magnetospheric plasma subject these particles to dissociation and ionization. The cloud morphologies and associated nitrogen plasma source rates are predicted in anticipation of Cassini data. Since the amount of molecular nitrogen ejected from Titan by photo-dissociation is small, molecular nitrogen ions detection by Cassini will be an indicator of atmospheric sputtering.
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... GE, Sing, DK, Herbert, F.: Nature 525, 511 (2007) Ben-Jaffel, L., Hosseini, S.: Astrophys. ... Academic Press, New York (1987) Chaufray, JY, Leblanc, F., Quemerais, E., Bertaux, JL: J. Geophys ... J. 709, 670 (2010) Holmström, M.,... more
... GE, Sing, DK, Herbert, F.: Nature 525, 511 (2007) Ben-Jaffel, L., Hosseini, S.: Astrophys. ... Academic Press, New York (1987) Chaufray, JY, Leblanc, F., Quemerais, E., Bertaux, JL: J. Geophys ... J. 709, 670 (2010) Holmström, M., Ekenbäck, A., Selsis, F., Penz, T., Lammer, H., Wurz, P ...
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ABSTRACT We perform numerical simulations of the molecular hydrogen production on the surface of interstellar dust grains and its dissociation by the ultraviolet background in conditions typical for the interstellar medium. The kinetic... more
ABSTRACT We perform numerical simulations of the molecular hydrogen production on the surface of interstellar dust grains and its dissociation by the ultraviolet background in conditions typical for the interstellar medium. The kinetic version of the Monte Carlo method is used for the modeling of the catalytic chemical reactions on the surface of the dust fraction and in the surrounding medium. Our simulations show the importance of the interstellar dust particles for hydrogen chemistry in diffuse molecular clouds.
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It is suggested that the incorporation of HCN in Titan's atmospheric haze may be an important process affecting the HCN profile and the C/N ratio in Titan's haze. By introducing a loss to the haze term for HCN (i.e. a production... more
It is suggested that the incorporation of HCN in Titan's atmospheric haze may be an important process affecting the HCN profile and the C/N ratio in Titan's haze. By introducing a loss to the haze term for HCN (i.e. a production term of ``poly-HCN") in the photochemical model of Lara et al. (1996), we have improved the model's ability to simultaneously reproduce the observed HCN and C_2 hydrocarbon profiles in Titan's lower stratosphere. The loss rate of HCN by this process may be a few times 10(8) cm(-2) s(-1) . The calculated C/N ratio in the haze, assuming that the haze is primarily produced from C_6H_2, C_8H_2 and ``poly-HCN", is approximately equal to 2, in agreement with the composition of laboratory tholin analogues.
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An analysis of the structure of the kinetic scales of collision processes in rarefied multicomponent systems suggests the possibility of developing structural numerical models that would provide high flexibility and efficiency when... more
An analysis of the structure of the kinetic scales of collision processes in rarefied multicomponent systems suggests the possibility of developing structural numerical models that would provide high flexibility and efficiency when implemented on state-of-the-art computers. In particular, it is shown that, by elaborating the kinetic scale structure, as the kinetic system approaches the state of thermal equilibrium or the steady state, it is possible to increase the speed of Monte Carlo algorithms in the numerical analysis of collision process kinetics. A stochastic structural model and results of calculations are presented.
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During a solar proton event atomic nitrogen is produced by the primary protons in dissociative ionisation of N2 and by the secondary electrons in dissociation of N2 . Furthermore, because of the ionisation caused by the primary protons,... more
During a solar proton event atomic nitrogen is produced by the primary protons in dissociative ionisation of N2 and by the secondary electrons in dissociation of N2 . Furthermore, because of the ionisation caused by the primary protons, the ion chemistry can produce atomic nitrogen as well as nitric oxide and be an important additional source of odd nitrogen. We