Altitude profile of H in the atmosphere of Venus from Lyman α observations of Venera 11 and Venera 12 and origin of the hot exospheric component

Bertaux, Jean-Loup; Lepine, V.M.; Kurt, V. G.; Смирнов, А. С.

doi:10.1016/0019-1035(82)90110-5

Cited by 53 publications

(20 citation statements)

References 35 publications

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“…The Venusian profile presents two scale heights corresponding to a cold hydrogen population dominant below 2000 km (∼1.3 Rv; where Rv is the Venus radius of 6051 km) and a hot hydrogen population dominant above 4000 (∼1.7 Rv) km. These two scale height profiles have already been observed by several previous missions to Venus (Anderson 1976;Bertaux et al 1978Bertaux et al , 1982Takacs et al 1980;Paxton et al 1988). On Mars, the Lyman-α brightness profile is rather constant between 400 km and 1000 km (1.2-1.4 Rm).…”

Section: Recent Observations Of Hydrogen Coronae By Uv Remote Sensingsupporting

confidence: 73%

Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan

et al. 2011

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International audienceOur understanding of the upper atmosphere of unmagnetized bodies such as Mars, Venus and Titan has improved significantly in this decade. Recent observations by in situ and remote sensing instruments on board Mars Express, Venus Express and Cassini have revealed characteristics of the neutral upper atmospheres (exospheres) and of energetic neutral atoms (ENAs). The ENA environment in the vicinity of the bodies is by itself a significant study field, but ENAs are also used as a diagnostic tool for the exosphere and the interaction with the upstream plasmas. Synergy between theoretical and modeling work has also improved considerably. In this review, we summarize the recent progress of our understanding of the neutral environment in the vicinity of unmagnetized planets

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Section: Recent Observations Of Hydrogen Coronae By Uv Remote Sensingsupporting

confidence: 73%

Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan

et al. 2011

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“…As described in Section 3, this implies that the hydrogen density also can be expressed as a double exponential. It is interesting to notice that this functional form replicates the two-temperature model that has been frequently used to analyze the hydrogen density on Venus [Takacs et al, 1980;Bertaux et al, 1982;Paxton and Anderson, 1992]. According to Paxton and Anderson [1992] such a two-component density profile also exists in the exospheres of Mars and Earth, but is hard to observe due to the large scale heights of thermal hydrogen on these two planets.…”

Section: Discussionmentioning

confidence: 63%

Neutral hydrogen density profiles derived from geocoronal imaging

et al. 2003

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[1] Measurements of the Lyman a column brightness by the Geocoronal Imager (GEO), part of the FUV imaging system on board the IMAGE satellite, have been used to derive an empirical model of the neutral hydrogen density distribution at high altitudes (>3.5 R E geocentric distance) on the night-side of the Earth. The model presented is an effort to provide the density profiles needed to analyze the energetic neutral atom imaging data at ring current altitudes and above. The variable solar Lyman a flux is obtained from the UARS/SOLSTICE measurements and the scattered solar Lyman a emissions from interplanetary hydrogen are obtained from a model. Assuming that the exosphere at high altitudes (>3.5 R E geocentric distance) can be considered as an optical thin medium and that the hydrogen density profile can be expressed as a double exponential we show that the Lyman a column brightness can be converted to hydrogen density profiles. The hydrogen density above 5 R E is found to be slightly higher for large solar zenith angles than for 90°solar zenith angle. The hydrogen density shows temporal variations which are not controlled by any solar quantity or geomagnetic parameter alone. Our Lyman a profiles and derived hydrogen density profiles are close to what was observed by Dynamics Explorer 1 [Rairden et al., 1986]. Above 8 R E we find higher densities than they did for all solar zenith angles >90°. We do not find any evidence of depletion due to charge exchange with solar wind protons outside the magnetopause. Our results are only valid above 3.5 R E .

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“…At this height, however, both the hydrogen and the hot oxygen densities are ∼10 2 cm −3 (Bertaux et al 1982;Nagy & Cravens 1988) and thus orders of magnitude too low. Furthermore, the ACIS-I spectrum of all events within 16.…”

Section: Discussionmentioning

confidence: 91%

Discovery of X–rays from Venus with Chandra

Dennerl

Burwitz

Englhauser

et al. 2002

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Abstract. On January 10 and 13, 2001, Venus was observed for the first time with an X-ray astronomy satellite. The observation, performed with the ACIS-I and LETG/ACIS-S instruments on Chandra, yielded data of high spatial, spectral, and temporal resolution. Venus is clearly detected as a half-lit crescent, with considerable brightening on the sunward limb. The morphology agrees well with that expected from fluorescent scattering of solar X-rays in the planetary atmosphere. The radiation is observed at discrete energies, mainly at the O-Kα energy of 0.53 keV. Fluorescent radiation is also detected from C-Kα at 0.28 keV and, marginally, from N-Kα at 0.40 keV. An additional emission line is indicated at 0.29 keV, which might be the signature of the C 1s → π transition in CO2 and CO. Evidence for temporal variability of the X-ray flux was found at the 2.6 σ level, with fluctuations by factors of a few times indicated on time scales of minutes. All these findings are fully consistent with fluorescent scattering of solar X-rays. No other source of X-ray emission was detected, in particular none from charge exchange interactions between highly charged heavy solar wind ions and atmospheric neutrals, the dominant process for the X-ray emission of comets. This is in agreement with the sensitivity of the observation.

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Altitude profile of H in the atmosphere of Venus from Lyman α observations of Venera 11 and Venera 12 and origin of the hot exospheric component

Cited by 53 publications

References 35 publications

Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan

Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan

Neutral hydrogen density profiles derived from geocoronal imaging

Discovery of X–rays from Venus with Chandra

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