UV and IR auroral emission model for the outer planets: Jupiter and Saturn comparison

Tao, Chihiro; Badman, S. V.; Fujimoto, M.

doi:10.1016/j.icarus.2011.04.001

Cited by 65 publications

(125 citation statements)

References 52 publications

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“…The electron densities in the hydrocarbon region in the Perry et al (1999) and Tao et al (2011) Jovian auroral models are of order 100 cm −3 , which is about the same as the predicted C 3 H 8 density from neutral photochemistry . Adopting these numbers in the production rate equations for the above reactions suggests that reactions 7-9 are, in combination, more than two orders of magnitude more effective in producing C 2 H 2 and C 2 H 4 than reaction 10 is in producing C 2 H 6 .…”

Section: Hydrocarbonssupporting

confidence: 60%

“…Qualitatively, we believe a similar conclusion applies to the upper atmospheric chemistry in the Jovian auroral regions, although the fact that molecular diffusion limits the vertical extent of CH 4 and other hydrocarbons near the homopause region makes this ion-chemistry source of neutrals less effective on Jupiter than on Titan. Several investigators have modeled ion chemistry in the auroral regions of Jupiter (e.g., Perry et al 1999;Wong et al 2003;Tao et al 2011). However, Perry et al (1999) and Tao et al (2011) keep the neutrals fixed in their model and do not consider how ion chemistry affects the neutral abundances.…”

Section: Hydrocarbonsmentioning

confidence: 99%

“…Several investigators have modeled ion chemistry in the auroral regions of Jupiter (e.g., Perry et al 1999;Wong et al 2003;Tao et al 2011). However, Perry et al (1999) and Tao et al (2011) keep the neutrals fixed in their model and do not consider how ion chemistry affects the neutral abundances. Wong et al (2003) fully couple the ion and neutral chemistry, but their focus is on benzene chemistry, and they do not discuss the dominant reactions affecting the neutral C 2 species.…”

Section: Hydrocarbonsmentioning

confidence: 99%

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Jupiter’s auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra

Sinclair

Orton

Greathouse

et al. 2017

Icarus

107

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Auroral processes are evident in Jupiter's polar atmosphere over a large range in wavelength (X-ray to radio). In particular, previous observations in the mid-infrared (5 to 15 µm) have shown enhanced emission from CH 4 , C 2 H 2 and C 2 H 4 and further stratospheric hydrocarbon species in spatial regions coincident with auroral processes observed at other wavelengths. These regions, described as auroral-related hotspots, observed at approximately 160• W to 200• W (System III) at high-northern latitudes and 330• W to 80• W at high-southern latitudes, indicate that auroral processes modify the thermal structure and composition of the neutral atmosphere. However, previous studies have struggled to differentiate whether the aforementioned enhanced emission is a result of either temperature changes and/or changes in the concentration of the emitting species. We attempt to address this degeneracy in this work by performing a retrieval analysis of Voyager 1-IRIS spectra (acquired in 1979) and Cassini-CIRS spectra (acquired in 2000/2001) of Jupiter. Retrievals of the vertical temperature profile in Cassini-CIRS spectra covering the auroral-related hotspots indicate the presence of two discrete vertical regions of heating at the 1-mbar level and at pressures of 10-µbar and lower. For example, in Cassini-CIRS 2.5 cm −1 'MIRMAP' spectra at 70• N (planetographic) 180• W (centred on the auroral oval), we find temperatures at the 1-mbar level and 10-µbar levels are enhanced by 15.3 ± 5.2 K and 29.6 ± 15.0 K respectively, in comparison to results at 70• N, 60• W in the same dataset. High temperatures at 10-µbar and lower pressures were considered indicative of joule heating, ion and/or electron precipitation, ion-drag and energy released form exothermic ion-chemistry. However, we conclude that the heating at the 1-mbar level is the result of either a layer of aurorally-produced haze particles, which are heated by incident sunlight and/or adiabatic heating by downwelling within the auroral hot-spot region. The former mechanism would be consistent with the vertical profiles of polycyclic aromatic hydrocarbons (PAHs) and haze particles predicted in auroral-chemistry models (Wong et al., 2000(Wong et al., , 2003. Retrievals of C 2 H 2 and C 2 H 6 were also performed and indicate C 2 H 2 is enriched but C 2 H 6 is depleted in auroral regions relative to quiescent regions. For example, using CIRS ∆ν = 2.5 cm −1 spectra, we determined that C 2 H 2 at 0.98 mbar increases by 175.3 ± 89.3 ppbv while C 2 H 6 at 4.7 mbar decreases by 0.86 ± 0.59 ppmv in comparing results at 70• N, 180• W and 70• N, 60• W. These results represent a mean of values retrieved from different initial assumptions and thus we believe they are robust. We believe these contrasts in C 2 H 2 and C 2 H 6 between auroral and quiescent regions can be explained by a coupling of auroral-driven chemistry and horizontal advection. Ion-neutral and electron recombination chemistry in the auroral region enriches all C 2 hydrocarbons but in particular, the unsaturated ...

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Section: Hydrocarbonssupporting

confidence: 60%

Section: Hydrocarbonsmentioning

confidence: 99%

Section: Hydrocarbonsmentioning

confidence: 99%

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Jupiter’s auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra

Sinclair

Orton

Greathouse

et al. 2017

Icarus

107

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show abstract

“…H 3 + , however, is sensitive to the conditions in the atmosphere, and could be an important diagnostic with strong emission features at 2 μm and 4 μm (Tao et al 2011(Tao et al , 2012Badman et al 2015). The ro-vibrational features are thermally excited and depend on the atmospheric temperature.…”

Section: Emission Line Featuresmentioning

confidence: 99%

A Panchromatic View of Brown Dwarf Aurorae

Pineda

Hallinan

Kao

2017

ApJ

118

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Stellar coronal activity has been shown to persist into the low-mass star regime, down to late M-dwarf spectral types. However, there is now an accumulation of evidence suggesting that at the end of the main sequence, there is a transition in the nature of the magnetic activity from chromospheric and coronal to planet-like and auroral, from local impulsive heating via flares and MHD wave dissipation to energy dissipation from strong large-scale magnetospheric current systems. We examine this transition and the prevalence of auroral activity in brown dwarfs through a compilation of multiwavelength surveys of magnetic activity, including radio, X-ray, and optical. We compile the results of those surveys and place their conclusions in the context of auroral emission as a consequence of large-scale magnetospheric current systems that accelerate energetic electron beams and drive the particles to impact the cool atmospheric gas. We explore the different manifestations of auroral phenomena, like Hα, in brown dwarf atmospheres and define their distinguishing characteristics. We conclude that large-amplitude photometric variability in the near-infrared is most likely a consequence of clouds in brown dwarf atmospheres, but that auroral activity may be responsible for long-lived stable surface features. We report a connection between auroral Hα emission and quiescent radio emission in electron cyclotron maser instability pulsing brown dwarfs, suggesting a potential underlying physical connection between quiescent and auroral emissions. We also discuss the electrodynamic engines powering brown dwarf aurorae and the possible role of satellites around these systems both to power the aurorae and seed the magnetosphere with plasma.

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“…Badman et al (2011) and Melin et al (2011Melin et al ( , 2014 or emitting species lifetime (Tao et al, 2011;Badman et al, 2014a).…”

mentioning

confidence: 99%

Saturn’s auroral morphology and field-aligned currents during a solar wind compression

Provan

Bunce

Mitchell

et al. 2016

Icarus

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UV and IR auroral emission model for the outer planets: Jupiter and Saturn comparison

Cited by 65 publications

References 52 publications

Jupiter’s auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra

Jupiter’s auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra

A Panchromatic View of Brown Dwarf Aurorae

Saturn’s auroral morphology and field-aligned currents during a solar wind compression

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