The origin and evolution of Saturn’s 2011–2012 stratospheric vortex

Fletcher, Leigh N.; Hesman, B. E.; Achterberg, R. K.; Irwin, Patrick; Bjoraker, G. L.; Gorius, N.; Hurley, J.; Sinclair, James; Orton, Glenn S.; Legarreta, J.; García-Melendo, E.; Sánchez‐Lavega, A.; Read, P. L.; Simon-Miller, A. A.; Flasar, F. M.

doi:10.1016/j.icarus.2012.08.024

Cited by 70 publications

(133 citation statements)

References 62 publications

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“…On 5 December 2010, a planetary-scale disturbance erupted in Saturn's northern hemisphere, leading to large temperature perturbations (up to 50 K at 0.5 mbar) in Saturn's stratosphere (e.g., Fletcher et al 2012). Perturbations in the troposphere were much more subdued, although Achterberg et al (2014) reported an increase of about 3 K in the far-IR (20-200 µm, probing the upper troposphere near 400 mbar) thermodynamic temperature at the storm's latitude.…”

Section: Saturnmentioning

confidence: 99%

Planckintermediate results

Akrami

Ashdown

Aumont

et al. 2017

A&A

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Measurements of flux density are described for five planets, Mars, Jupiter, Saturn, Uranus, and Neptune, across the six Planck High Frequency Instrument frequency bands (100-857 GHz) and these are then compared with models and existing data. In our analysis, we have also included estimates of the brightness of Jupiter and Saturn at the three frequencies of the Planck Low Frequency Instrument (30, 44, and 70 GHz). The results provide constraints on the intrinsic brightness and the brightness time-variability of these planets. The majority of the planet flux density estimates are limited by systematic errors, but still yield better than 1% measurements in many cases. Applying data from Planck HFI, the Wilkinson Microwave Anisotropy Probe (WMAP), and the Atacama Cosmology Telescope (ACT) to a model that incorporates contributions from Saturn's rings to the planet's total flux density suggests a best fit value for the spectral index of Saturn's ring system of β ring = 2.30 ± 0.03 over the 30-1000 GHz frequency range. Estimates of the polarization amplitude of the planets have also been made in the four bands that have polarizationsensitive detectors (100-353 GHz); this analysis provides a 95 % confidence level upper limit on Mars's polarization of 1.8, 1.7, 1.2, and 1.7 % at 100, 143, 217, and 353 GHz, respectively. The average ratio between the Planck-HFI measurements and the adopted model predictions for all five planets (excluding Jupiter observations for 353 GHz) is 0.997, 0.997, 1.018, and 1.032 for 100, 143, 217, and 353 GHz, respectively. Model predictions for planet thermodynamic temperatures are therefore consistent with the absolute calibration of Planck-HFI detectors at about the three-percent-level. We compare our measurements with published results from recent cosmic microwave background experiments. In particular, we observe that the flux densities measured by Planck HFI and WMAP agree to within 2 %. These results allow experiments operating in the mm-wavelength range to cross-calibrate against Planck and improve models of radiative transport used in planetary science.

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Section: Saturnmentioning

confidence: 99%

Planckintermediate results

Akrami

Ashdown

Aumont

et al. 2017

A&A

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“…The Saturn thermodynamical data from Moses et al (2000), Moore et al (2004) (solid line) and Galand et al (2009) (dashed line) were used to derive the degree of ionisation [courtesy: Alejandro Luque]. Saturn's disk-integrated spectrum is based on the latest profiles of atmospheric temperature and gaseous composition derived from retrieval analysis of Cassini Composite Infrared Spectrometer spectra (Irwin et al 2008;Fletcher et al 2012;courtesy: Leigh Fletcher). The brown dwarf spectra are from Cushing et al (2005) [courtesy: Sarah Casewell], the atmosphere models from Witte et al (2011) [courtesy: Isabel Rodrigues-Barrera].…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Electrification in Dusty, Reactive Gases in the Solar System and Beyond

et al. 2016

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Detailed observations of the solar system planets reveal a wide variety of local atmospheric conditions. Astronomical observations have revealed a variety of extrasolar planets none of which resembles any of the solar system planets in full. Instead, the most massive amongst the extrasolar planets, the gas giants, appear very similar to the class of (young) brown dwarfs which are amongst the oldest objects in the Universe. Despite this diversity, solar system planets, extrasolar planets and brown dwarfs have broadly similar global temperatures between 300 and 2500 K. In consequence, clouds of different chemical species form in their atmospheres. While the details of these clouds differ, the fundamental physical processes are the same. Further to this, all these objects were observed to produce radio and X-ray emissions. While both kinds of radiation are well studied on Earth and to a lesser extent on the solar system planets, the occurrence of emissions that potentially originate from accelerated electrons on brown dwarfs, extrasolar planets and protoplanetary disks is not well understood yet. This paper offers an interdisciplinary view on electrification processes and their feedback on their hosting environment in meteorology, volcanology, planetology and research on extrasolar planets and planet formation.

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“…One of these cells was located directly above the tropospheric storm head (Fletcher et al 2011). These warm airmasses traveling at different velocities in the atmosphere of Saturn merged in late April 2011 to form a huge warm vortex, in which temperature increases of up to 80 K were recorded in the 2 mbar region in May 2011 (Fletcher et al 2012a). Although continuously shrinking in longitude and cooling radiatively since July 2011, this huge anticyclonic vortex left an observable thermal signature still detectable as of 2014.…”

Section: Introductionmentioning

confidence: 99%

“…Infrared observations with Cassini/CIRS and ground-based facilities (Very Large Telescope, NASA Infrared Telescope Facility, McMath-Pierce Telescope) have allowed us to monitor the evolution of stratospheric temperatures and hydrocarbon abundances (Fletcher et al 2012a;Hesman et al 2012Hesman et al , 2013bHesman et al , 2015. Acetylene and ethylene have seen their ∼2 mbar mole fractions increase by a factor of ∼3 and ∼100, respectively, at the time of the merging of the two beacons, while the mole fraction of ethane remained mostly unchanged, to within the levels of uncertainty on the spectral inversions.…”

Section: Introductionmentioning

confidence: 99%

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Photochemical response to the variation of temperature in the 2011−2012 stratospheric vortex of Saturn

Cavalié¹,

Dobrijévic²,

Fletcher³

et al. 2015

A&A

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Context. A hot vortex formed in the stratosphere of Saturn following the 2010−2011 Northern Storm. Huge temperature increases have been measured in the vortex around the millibar level. Enhancements in hydrocarbon abundances have been observed at the millibar level in 2011−2012 inside this vortex. Aims. We model the time-dependent photochemistry inside the vortex by accounting for the temperature variability over the period from January 2011 to March 2012 to assess whether photochemistry alone can explain the enhancements seen in the hydrocarbon abundances. Methods. We used a 1D time-dependent photochemical model of Saturn and adapted it to the perturbed conditions of the vortex after validating it in quiescent conditions. Results. Our model predicts non-variability for ethane (C 2 H 6 ) and acetylene (C 2 H 2 ) and an increase in ethylene (C 2 H 4 ) by a factor of 3 in the mbar region. Heavier hydrocarbons show a stronger variability than the lighter ones. We are unable to reproduce the increase seen in C 2 H 2 , and we significantly underestimate the increase seen in C 2 H 4 . Conclusions. Pure photochemistry does not explain the variability seen in the abundance of most hydrocarbons. This means that dynamics (eddy diffusion and/or advection) must have played a significant role in shaping the vertical profiles of the main hydrocarbons.

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The origin and evolution of Saturn’s 2011–2012 stratospheric vortex

Cited by 70 publications

References 62 publications

Planckintermediate results

Planckintermediate results

Atmospheric Electrification in Dusty, Reactive Gases in the Solar System and Beyond

Photochemical response to the variation of temperature in the 2011−2012 stratospheric vortex of Saturn

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