Sunlight refraction in the mesosphere of Venus during the transit on June 8th, 2004

Tanga, P.; Widemann, T.; Sicardy, B.; Pasachoff, Jay M.; Arnaud, J.; Comolli, Lorenzo; Rondi, A.; Rondi, S.; Sütterlin, P.

doi:10.1016/j.icarus.2011.12.004

Cited by 31 publications

(55 citation statements)

References 43 publications

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“…This is because the aureole is much dimmer than the photosphere and therefore difficult to distinguish from direct solar radiation. Generally, the intensity of the aureole increases with the proportion of the Venusian disc sitting inside the solar disc (Tanga et al 2012). Therefore, observations taken right before second contact (such as the ingress image) or right after third contact give the closest direct indication of the intensity of the aureole when the Venusian disc is entirely within the solar disc.…”

Section: Refraction Of Solar Radiation In the Venusian Atmospherementioning

confidence: 99%

“…-Two, that the intensity of the aureole does not change with azimuth. Tanga et al (2012) recently published a model of aureole intensity, relating it to the spatial distribution of photospheric intensity and physical structure of the Venusian atmosphere. This is, to our knowledge, the only model of its kind reported in the literature.…”

Section: Refraction Of Solar Radiation In the Venusian Atmospherementioning

confidence: 99%

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Point spread function of SDO/HMI and the effects of stray light correction on the apparent properties of solar surface phenomena

Yeo

Feller

Solanki

et al. 2013

A&A

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Aims. We present a point spread function (PSF) for the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) and discuss the effects of its removal on the apparent properties of solar surface phenomena in HMI data. Methods. The PSF was retrieved from observations of Venus in transit by matching it to the convolution of a model of the Venusian disc and solar background with a guess PSF. We described the PSF as the sum of five Gaussian functions, the amplitudes of which vary sinusoidally with azimuth. This relatively complex functional form was required by the data. Observations recorded near in time to the transit of Venus were corrected for instrumental scattered light by the deconvolution with the PSF. We also examined the variation in the shape of the solar aureole in daily data, as an indication of PSF changes over time.Results. Granulation contrast in restored HMI data is greatly enhanced relative to the original data and exhibit reasonable agreement with numerical simulations. Image restoration enhanced the apparent intensity and pixel averaged magnetic field strength of photospheric magnetic features significantly. For small-scale magnetic features, restoration enhanced intensity contrast in the continuum and core of the Fe I 6173 Å line by a factor of 1.3, and the magnetogram signal by a factor of 1.7. For sunspots and pores, the enhancement varied strongly within and between features, being more acute for smaller features. Magnetic features are also rendered smaller, as signal smeared onto the surrounding quiet Sun is recovered. Image restoration increased the apparent amount of magnetic flux above the noise floor by a factor of about 1.2, most of the gain coming from the quiet Sun. Line-of-sight velocity due to granulation and supergranulation is enhanced by a factor of 1.4 to 2.1, depending on position on the solar disc. The shape of the solar aureole varied, with time and between the two CCDs. There are also indications that the PSF varies across the FOV. However, all these variations were found to be relatively small, such that a single PSF can be applied to HMI data from both CCDs, over the period examined without introducing significant error. Conclusions. Restoring HMI observations with the PSF presented here returns a reasonable estimate of the stray light-free intensity contrast. Image restoration affects the measured radiant, magnetic and dynamic properties of solar surface phenomena sufficiently to significantly impact interpretation.

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Section: Refraction Of Solar Radiation In the Venusian Atmospherementioning

confidence: 99%

Section: Refraction Of Solar Radiation In the Venusian Atmospherementioning

confidence: 99%

Point spread function of SDO/HMI and the effects of stray light correction on the apparent properties of solar surface phenomena

Yeo

Feller

Solanki

et al. 2013

A&A

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“…Finally, because of the rarity and uniqueness, the results of some inferences about upper atmosphere thermal structure from the analysis of the aureole observations during the transit of Venus across the solar observed from spacecraft and ground based telescopes are also worth mentioning Tanga et al 2012) as analog for atmospheres of terrestrial exoplanets. More details of the ground based observations can be found in the intercomparison of recent observations reported by .…”

Section: Ground Based Observations Of Temperature Structurementioning

confidence: 99%

Venus Atmospheric Thermal Structure and Radiative Balance

et al. 2018

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From the discovery that Venus has an atmosphere during the 1761 transit by M. Lomonosov to the current exploration of the planet by the Akatsuki orbiter, we continue to learn about the planet's extreme climate and weather. This chapter attempts to provide a comprehensive but by no means exhaustive review of the results of the atmospheric thermal structure and radiative balance since the earlier works published in Venus and Venus II books from recent spacecraft and Earth based investigations and summarizes the gaps in [1411][1412][1413][1414] 1986). Thus, most of the new information about the atmospheric thermal structure has come from different remote sensing (Earth based and spacecraft) techniques using occultations (solar infrared, stellar ultraviolet and orbiter radio occultations), spectroscopy and microwave, short wave and thermal infrared emissions. The results are restricted to altitudes higher than about 40 km, except for one investigation of the near surface static stability inferred by Meadows and Crisp (J. Geophys. Res. 101:4595-4622, 1996) from 1 μm observations from Earth. Little information about the lower atmospheric structure is possible below about 40 km altitude from radio occultations due to large bending angles. The gaps in our knowledge include spectral albedo variations over time, vertical variation of the bulk composition of the atmosphere (mean molecular weight), the identity, properties and abundances of absorbers of incident solar radiation in the clouds. The causes of opacity variations in the nightside cloud cover and vertical gradients in the deep atmosphere bulk composition and its impact on static stability are also in need of critical studies. The knowledge gaps and questions about Venus and its atmosphere provide the incentive for obtaining the necessary measurements to understand the planet, which can provide some clues to learn about terrestrial exoplanets.

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“…Historically, the varying extension of the halo cusps was key to establishing the existence of a Venus atmosphere (Russell 1899). This diffuse halo differs from the refraction halo that becomes visible during the ingress and egress phases of a Venus transit across the solar disk (García Muñoz & Mills 2012;Tanga et al 2012). Feature I must not be mistaken for specular reflection at the planet surface, a mechanism that might also produce brightness excesses at large phase angles for planets with a liquid surface (Williams & Gaidos 2008;Robinson et al 2010).…”

Section: Venus Phase Curvesmentioning

confidence: 99%

Glory revealed in disk-integrated photometry of Venus

Muñoz

Pérez‐Hoyos

Sánchez‐Lavega

2014

A&A

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Context. Reflected light from a spatially unresolved planet yields unique insight into the overall optical properties of the planet cover. Glories are optical phenomena caused by light that is backscattered within spherical droplets following a narrow distribution of sizes; they are well known on Earth as localised features above liquid clouds. Aims. Here we report the first evidence for a glory in the disk-integrated photometry of Venus and, in turn, of any planet. Methods. We used previously published phase curves of the planet that were reproduced over the full range of phase angles with model predictions based on a realistic description of the Venus atmosphere. We assumed that the optical properties of the planet as a whole can be described by a uniform and stable cloud cover, an assumption that agrees well with observational evidence. Results. We specifically show that the measured phase curves mimic the scattering properties of the Venus upper-cloud micron-sized aerosols, also at the small phase angles at which the glory occurs, and that the glory contrast is consistent with what is expected after multiple scattering of photons. In the optical, the planet appears to be brighter at phase angles of ∼11-13 • than at full illumination; it undergoes a maximum dimming of up to ∼10% at phases in between. Conclusions. Glories might potentially indicate spherical droplets and, thus, extant liquid clouds in the atmospheres of exoplanets. A prospective detection will require exquisite photometry at the small planet-star separations of the glory phase angles.

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Sunlight refraction in the mesosphere of Venus during the transit on June 8th, 2004

Abstract: International audienc

Cited by 31 publications

References 43 publications

Point spread function of SDO/HMI and the effects of stray light correction on the apparent properties of solar surface phenomena

Point spread function of SDO/HMI and the effects of stray light correction on the apparent properties of solar surface phenomena

Venus Atmospheric Thermal Structure and Radiative Balance

Glory revealed in disk-integrated photometry of Venus

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