Cassini VIMS observations of H<sub>3</sub><sup>+</sup> emission on the nightside of Jupiter

Stallard, T.; Melin, Henrik; Miller, Steve; Baines, K. H.; Brown, R. H.; Blake, James; O’Donoghue, James; Johnson, R. E.; Bools, Bethany; Pilkington, N. M.; East, Oliver; Fletcher, M.

doi:10.1002/2015ja021097

Cited by 14 publications

(14 citation statements)

References 37 publications

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“…Where e * is a fast electron and EUV is an extreme ultraviolet photon from the Sun. As soon as H + 2 is created by reactions (1) -(3), reaction 4takes place almost instanteously (Miller et al, 2010;Stallard et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere

O’Donoghue

Moore

Connerney

et al. 2019

Icarus

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In this study we performed a new analysis of ground-based observations that were taken on 17 April 2011 using the 10-metre Keck telescope on Mauna Kea, Hawaii. Emissions from H + 3 , a major ion in Saturn's ionosphere, were previously analyzed from these observations, indicating that peaks in emission at specific latitudes were consistent with an influx of charged water products from the rings known as 'ring rain'. Subsequent modeling showed that these peaks in emission are best explained by an increase in H + 3 density, rather than in column-averaged H + 3 temperatures, as a local reduction in electron density (due to charge exchange with water) lengthens the lifetime of H + 3. However, what has been missing until now is a direct derivation of the H + 3 parameters temperature, density and radiative cooling rates, which are required to confirm and expand on existing models and theory. Here we present measurements of these H + 3 parameters for the first time in the non-auroral regions of Saturn, using two H + 3 lines, Q(1,0 −) and R(2,2). We confirm that H + 3 density is enhanced near the expected 'ring rain' planetocentric latitudes near 45 • N and 39 • S. A low H + 3 density near 31 • S, an expected prodigious source of water, may indicate that the rings are 'overflowing' material into the planet such that H + 3 destruction by charge-exchange with incoming neutrals outweighs its lengthened lifetime due to the aforementioned reduction

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Section: Introductionmentioning

confidence: 99%

Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere

O’Donoghue

Moore

Connerney

et al. 2019

Icarus

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“…[]; in this work values < 350 K are reported, while temperatures as high as 500–850 K were observed on the bright 3 µm spots imaged using the Gemini Near‐InfraRed Spectrograph data. Also the H 3 + temperatures retrieved in our study are systematically lower than those reported in the literature for the VIMS spectra [ Stallard et al ., ] and ground‐based data [ Lam et al ., ; Stallard et al ., ; Raynaud et al ., ; Lystrup et al ., ] which are around 800–1000 K. We have repeated the analysis of the spectrum of the orange area including only H 3 + in the simulation. In this case the H 3 + retrieved temperature is 1109.10 ± 32.2 K, closer to the one obtained by previous works.…”

Section: Discussionmentioning

confidence: 98%

Mapping of hydrocarbons and H₃⁺ emissions at Jupiter's north pole using Galileo/NIMS data

Altieri

Dinelli

Migliorini

et al. 2016

Geophysical Research Letters

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In this paper we report the mapping of H3+, C2H2, and CH4 as derived by an unexploited Galileo/Near‐Infrared Mapping Spectrometer (NIMS) data set. As previously observed, hydrocarbons emissions appear to be located in the internal part of the auroral main oval, where CH4 3 µm vibrational band intensity ratios suggest that nonthermal excitation mechanisms, such as auroral particle precipitation and/or Joule heating, are responsible for the observed emissions. Temperature estimation are in good agreement for the CH4‐emitting region on the hot spot, while the values obtained for H3+ are lower in comparison with Cassini/visual and infrared mapping spectrometer and ground‐based data. C2H2 emission overlaps the CH4 one only at higher latitudes >75°N, indicating that different energetic particles are at work inside the main oval polar ward. CH4 is also found on the northern section of the main oval (135°< longitude <190°, 60°< latitude <90°N). The present investigation results have implications on the Juno/Jovian InfraRed Auroral Mapper observation planning as well as on the codes that will be used to retrieve temperatures and densities of all the emitting species involved in the Jupiter auroral processes.

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“…Lower concentrations of

{H_{3}}^{+}

make up the disk population in Jupiter's ionosphere. This population is generated from the fast chain reaction beginning with ionization by solar EUV [ Lam et al , 1997; Miller et al , 1997], as shown in equation , and does not exist in the nightside ionosphere of Jupiter [ Stallard et al , 2015].

H_{2} + e^{-} \to {H_{2}}^{+} + e^{-} + e^{-}

H_{2} + italichν \to {H_{2}}^{+} + e^{-}

{H_{2}}^{+} + H_{2} \to {H_{3}}^{+} + normalH

…”

Section: Introductionmentioning

confidence: 99%

Jupiter's polar ionospheric flows: High resolution mapping of spectral intensity and line‐of‐sight velocity of H₃⁺ ions

et al. 2017

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We present a detailed study of the H3+ auroral emission at Jupiter, which uses data taken on 31 December 2012 with the long‐slit echelle spectrometer Cryogenic Infrared Echelle Spectrograph (European Southern Observatory's Very Large Telescope). The entire northern auroral region was observed using significantly more slit positions than previous studies, providing a highly detailed view of ionospheric flows, which were mapped onto polar projections. Previous observations of ionospheric flows in Jupiter's northern auroral ionosphere, using the long‐slit echelle spectrometer CSHELL (NASA Infrared Telescope Facility) to measure the Doppler‐shifted H3+ ν2 Q(1,0−) line at 3.953 μm, showed a strongly subrotating region that was nearly stationary in the inertial magnetic frame of reference, suggesting an interaction with the solar wind. In this work, we observe this stationary region coincident with a polar region with very weak infrared emission, typically described as the dark region in UV observations. Although our observations cannot determine the exact mechanisms of this coupling, the coincidence between solar wind controlled ionospheric flows and a region with very low auroral brightness may provide new insights into the nature of the solar wind coupling. We also detected a superrotating ionospheric flow measured both at and equatorward of the narrow bright portion of the main auroral emission. The origin of this flow remains uncertain. Additionally, we detect a strong velocity shear poleward of the peak in brightness of the main auroral emission. This is in agreement with past models which predict that conductivity, as well as velocity shear, plays an important role in generating the main auroral emission.

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Cassini VIMS observations of H₃⁺ emission on the nightside of Jupiter

Cited by 14 publications

References 37 publications

Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere

Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere

Mapping of hydrocarbons and H₃⁺ emissions at Jupiter's north pole using Galileo/NIMS data

Jupiter's polar ionospheric flows: High resolution mapping of spectral intensity and line‐of‐sight velocity of H₃⁺ ions

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Cassini VIMS observations of H3+ emission on the nightside of Jupiter

Cited by 14 publications

References 37 publications

Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere

Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere

Mapping of hydrocarbons and H3+ emissions at Jupiter's north pole using Galileo/NIMS data

Jupiter's polar ionospheric flows: High resolution mapping of spectral intensity and line‐of‐sight velocity of H3+ ions

Contact Info

Product

Resources

About

Cassini VIMS observations of H₃⁺ emission on the nightside of Jupiter

Mapping of hydrocarbons and H₃⁺ emissions at Jupiter's north pole using Galileo/NIMS data

Jupiter's polar ionospheric flows: High resolution mapping of spectral intensity and line‐of‐sight velocity of H₃⁺ ions