A multiwavelength investigation of the ring effect in the day sky spectrum

Pallamraju, Duggirala; Baumgardner, J.; Chakrabarti, Supriya

doi:10.1029/1999gl010961

Cited by 36 publications

(45 citation statements)

References 16 publications

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“…This also minimizes any potential errors arising from the absorption by O 3 (≈1% peak-to-valley differential absorption for SZA=75 • and 350 DU) or the very weak broad O 4 absorption feature at 343.4 nm (Greenblatt et al, 1990) which cannot be neglected at larger SZA. FI was also measured for eight other Fraunhofer lines between 333.7 and 374.6 nm, and was found to increase with line depth in agreement with other measurements (Pallamraju et al, 2000). Figure 2 shows the day-to-day variation in FI for five mornings in late July where the sky was cloud-free as the sun passed through SZA=40±1 • .…”

Section: Measurement Resultssupporting

confidence: 68%

On the variability of the Ring effect in the near ultraviolet: understanding the role of aerosols and multiple scattering

et al. 2007

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Abstract. The "filling-in" (FI) of Fraunhofer lines, often referred to as the Ring effect, was examined using measurements of near ultraviolet sunlight scattered from the zenith sky above Boulder, Colorado during July and August 2005. The FI of the 344.1 nm Fe I line was directly determined by comparing direct sun and cloud-free zenith sky spectra recorded on the same day. The results, obtained over solar zenith angles (SZA) from 20 • to 70 • , are compared to the predictions of a simple rotational Raman Scattering (RRS) spectral model. The measured FI was found to be up to 70% greater than that predicted by first-order molecular scattering with a much stronger SZA dependence. Simultaneously measured aerosol optical depths and Monte Carlo calculations show that the combination of aerosol scattering and second-order molecular scattering can account for these differences, and potentially explain the contradictory SZA dependences in previously published measurements of FI. These two scattering processes also introduce a wavelength dependence to FI that complicates the fitting of diffuse sunlight observations in differential optical absorption spectroscopy (DOAS). A simple correction to improve DOAS retrievals by removing this wavelength dependence is described.

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Section: Measurement Resultssupporting

confidence: 68%

On the variability of the Ring effect in the near ultraviolet: understanding the role of aerosols and multiple scattering

et al. 2007

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“…Kattawar et al (1981) report a filling-in of 2.5% at 6301.5 Å for a Fe-I line. Brinkmann (1968) calculates a filling-in of about 1.7 in the center to 1.9% in the wings for a hypothetical line at 4000 Å, underlining the continuous and smooth effect across the line profile, which is also measured by Pallamraju et al (2000). Brinkmann (1968) reports observations showing a decrease of the filling-in with wavelength by a factor of 2 between 4383 and 6563 Å, and more recent measurements (Pallamraju et al 2000, Fig.…”

Section: Results From Eq (1) (Method1)mentioning

confidence: 97%

The Earth as an extrasolar transiting planet

Arnold

Ehrenreich

Vidal‐Madjar

et al. 2014

A&A

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Context. The atmospheric composition of transiting exoplanets can be characterized during transit by spectroscopy. Detections of several chemical species have previously been reported in the atmosphere of gaseous giant exoplanets. For the transit of an Earth twin, models predict that biogenic oxygen (O 2 ) and ozone (O 3 ) atmospheric gases should be detectable, as well as water vapour (H 2 O), a molecule linked to habitability as we know it on Earth. Aims. The aim is to measure the Earth radius versus wavelength λ -or the atmosphere thickness h(λ) -at the highest spectral resolution available to fully characterize the signature of Earth seen as a transiting exoplanet. Methods. We present observations of the Moon eclipse of December 21, 2010. Seen from the Moon, the Earth eclipses the Sun and opens access to the Earth atmosphere transmission spectrum. We used two different ESO spectrographs (HARPS and UVES) to take penumbra and umbra high-resolution spectra from ≈3100 to 10 400 Å. A change of the quantity of water vapour above the telescope compromised the quality of the UVES data. We corrected for this effect in the data processing. We analyzed the data by three different methods. The first method is based on the analysis of pairs of penumbra spectra. The second makes use of a single penumbra spectrum, and the third of all penumbra and umbra spectra. Results. Profiles h(λ) are obtained with the three methods for both instruments. The first method gives the best result, in agreement with a model. The second method seems to be more sensitive to the Doppler shift of solar spectral lines with respect to the telluric lines. The third method makes use of umbra spectra, which bias the result by increasing the overall negative slope of h(λ). It can be corrected for this a posteriori from results with the first method. The three methods clearly show the spectral signature of the Rayleigh scattering in the Earth atmosphere and the bands of H 2 O, O 2 , and O 3 . Sodium is detected. Assuming no atmospheric perturbations, we show that the E-ELT is theoretically able to detect the O 2 A-band in 8 h of integration for an Earth twin at 10 pc. Conclusions. Biogenic O 2 , O 3 , and water vapour are detected in Earth observed as a transiting planet, and, in principle, would be within reach of the E-ELT for an Earth twin at 10 pc.

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“…The details on the Ring effect variation and the procedure employed for the data reduction to obtain the daytime emissions using HIRISE have been described in detail elsewhere (Pallamraju et al, 2000;2002). In this study we discuss the behavior of observed emission rates on different days, both with and without geomagnetic storm occurrence.…”

Section: Instrumentationmentioning

confidence: 99%

“…The main challenge for the daytime optical measurements is the strong solar background continuum, which is approximately three orders of magnitude brighter than the daytime airglow emissions. At Boston University we have developed a high-resolution (0.12Å at 630.0 nm) imaging echelle spectrograph called the HIRISE (Pallamraju et al, 2002), which has been used to understand the Ring effect variation in the sky spectrum as opposed to the Fraunhofer spectrum (Pallamraju et al, 2000), observations of the sunlit auroral arcs (Pallamraju et al, 2001), and the daytime magnetospheric cusps (Pallamraju et al, 2004) in the OI 630.0 nm emissions.…”

Section: Instrumentationmentioning

confidence: 99%

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

2004

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Abstract.We describe the effect of the 6 November 2001 magnetic storm on the low latitude thermospheric composition. Daytime red line (OI 630.0 nm) emissions from Carmen Alto, Chile showed anomalous 2-3 times larger emissions in the morning (05:30-08:30 Local Time; LT) on the disturbed day compared to the quiet days. We interpret these emission enhancements to be caused due to the increase in neutral densities over low latitudes, as a direct effect of the geomagnetic storm. As an aftereffect of the geomagnetic storm, the dayglow emissions on the following day show gravity wave features that gradually increase in periodicities from around 30 min in the morning to around 100 min by the evening. The integrated dayglow emissions on quiet days show day-to-day variabilities in spatial structures in terms of their movement away from the magnetic equator in response to the Equatorial Ionization Anomaly (EIA) development in the daytime. The EIA signatures in the daytime OI 630.0 nm column-integrated dayglow emission brightness show different behavior on days with and without the post-sunset Equatorial Spread F (ESF) occurrence.

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A multiwavelength investigation of the ring effect in the day sky spectrum

Cited by 36 publications

References 16 publications

On the variability of the Ring effect in the near ultraviolet: understanding the role of aerosols and multiple scattering

On the variability of the Ring effect in the near ultraviolet: understanding the role of aerosols and multiple scattering

The Earth as an extrasolar transiting planet

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

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A multiwavelength investigation of the ring effect in the day sky spectrum

Cited by 36 publications

References 16 publications

On the variability of the Ring effect in the near ultraviolet: understanding the role of aerosols and multiple scattering

On the variability of the Ring effect in the near ultraviolet: understanding the role of aerosols and multiple scattering

The Earth as an extrasolar transiting planet

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(&lt;sup&gt;1&lt;/sup&gt;D) dayglow measurements from Chile

Contact Info

Product

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Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile