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Moore L, Moses JI, Melin H, Stallard TS, O’Donoghue J. Atmospheric implications of the lack of H 3+ detection at Neptune. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20200100. [PMID: 33161862 PMCID: PMC7658779 DOI: 10.1098/rsta.2020.0100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/02/2020] [Indexed: 05/04/2023]
Abstract
H3+ has been detected at all of the solar system giant planets aside from Neptune. Current observational upper limits imply that there is far less H3+ emission at Neptune than rudimentary modelling would suggest. Here, we explore via modelling a range of atmospheric conditions in order to find some that could be consistent with observational constraints. In particular, we consider that the upper atmosphere might be much cooler than it was during the 1989 Voyager 2 encounter, and we examine the impact of an enhanced influx of external material that could act to reduce H3+ density. Resulting ionosphere models that are consistent with existing H3+ observational constraints have an exospheric temperature of 450 K or less, 300 K lower than the Voyager 2 value. Alternatively, if a topside CO influx of 2 × 108 cm-2 s-1 is imposed, the upper atmospheric temperature can be higher, up to 550 K. The potential cooling of Neptune's atmosphere is relevant for poorly understood giant planet thermospheric energetics, and would also impact aerobreaking manoeuvers for any future spacecraft. Such a large CO influx, if present, could imply Triton is a very active moon with prominent atmospheric escape, and/or that Neptune's rings significantly modify its upper atmosphere, and the introduction of so much exogenic material would complicate interpretation of the origin of species observed in Neptune's lower atmosphere. This article is part a discussion meeting issue 'Future exploration of ice giant systems'.
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Affiliation(s)
- L. Moore
- Boston University, Boston, MA, USA
| | | | - H. Melin
- University of Leicester, Leicester, UK
| | | | - J. O’Donoghue
- JAXA Institute of Space and Astronautical Science, Tokyo, Japan
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2
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Saturn's near-equatorial ionospheric conductivities from in situ measurements. Sci Rep 2020; 10:7932. [PMID: 32404966 PMCID: PMC7220909 DOI: 10.1038/s41598-020-64787-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 04/21/2020] [Indexed: 11/08/2022] Open
Abstract
Cassini's Grand Finale orbits provided for the first time in-situ measurements of Saturn's topside ionosphere. We present the Pedersen and Hall conductivities of the top near-equatorial dayside ionosphere, derived from the in-situ measurements by the Cassini Radio and Wave Plasma Science Langmuir Probe, the Ion and Neutral Mass Spectrometer and the fluxgate magnetometer. The Pedersen and Hall conductivities are constrained to at least 10-5-10-4 S/m at (or close to) the ionospheric peak, a factor 10-100 higher than estimated previously. We show that this is due to the presence of dusty plasma in the near-equatorial ionosphere. We also show the conductive ionospheric region to be extensive, with thickness of 300-800 km. Furthermore, our results suggest a temporal variation (decrease) of the plasma densities, mean ion masses and consequently the conductivities from orbit 288 to 292.
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Wahlund JE, Morooka MW, Hadid LZ, Persoon AM, Farrell WM, Gurnett DA, Hospodarsky G, Kurth WS, Ye SY, Andrews DJ, Edberg NJT, Eriksson AI, Vigren E. In situ measurements of Saturn's ionosphere show that it is dynamic and interacts with the rings. Science 2017; 359:66-68. [PMID: 29229651 DOI: 10.1126/science.aao4134] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 11/27/2017] [Indexed: 11/02/2022]
Abstract
The ionized upper layer of Saturn's atmosphere, its ionosphere, provides a closure of currents mediated by the magnetic field to other electrically charged regions (for example, rings) and hosts ion-molecule chemistry. In 2017, the Cassini spacecraft passed inside the planet's rings, allowing in situ measurements of the ionosphere. The Radio and Plasma Wave Science instrument detected a cold, dense, and dynamic ionosphere at Saturn that interacts with the rings. Plasma densities reached up to 1000 cubic centimeters, and electron temperatures were below 1160 kelvin near closest approach. The density varied between orbits by up to two orders of magnitude. Saturn's A- and B-rings cast a shadow on the planet that reduced ionization in the upper atmosphere, causing a north-south asymmetry.
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Affiliation(s)
- J-E Wahlund
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden.
| | - M W Morooka
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - L Z Hadid
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - A M Persoon
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - W M Farrell
- Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - D A Gurnett
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - G Hospodarsky
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - W S Kurth
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - S-Y Ye
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - D J Andrews
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - N J T Edberg
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - A I Eriksson
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - E Vigren
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
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Laskina O, Morris HS, Grandquist JR, Qin Z, Stone EA, Tivanski AV, Grassian VH. Size matters in the water uptake and hygroscopic growth of atmospherically relevant multicomponent aerosol particles. J Phys Chem A 2015; 119:4489-97. [PMID: 25521409 DOI: 10.1021/jp510268p] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Understanding the interactions of water with atmospheric aerosols is crucial for determining the size, physical state, reactivity, and climate impacts of this important component of the Earth's atmosphere. Here we show that water uptake and hygroscopic growth of multicomponent, atmospherically relevant particles can be size dependent when comparing 100 nm versus ca. 6 μm sized particles. It was determined that particles composed of ammonium sulfate with succinic acid and of a mixture of chlorides typical of the marine environment show size-dependent hygroscopic behavior. Microscopic analysis of the distribution of components within the aerosol particles show that the size dependence is due to differences in the mixing state, that is, whether particles are homogeneously mixed or phase separated, for different sized particles. This morphology-dependent hygroscopicity has consequences for heterogeneous atmospheric chemistry as well as aerosol interactions with electromagnetic radiation and clouds.
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Affiliation(s)
- Olga Laskina
- †Department of Chemistry, and ‡Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States
| | - Holly S Morris
- †Department of Chemistry, and ‡Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States
| | - Joshua R Grandquist
- †Department of Chemistry, and ‡Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States
| | - Zhen Qin
- †Department of Chemistry, and ‡Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States
| | - Elizabeth A Stone
- †Department of Chemistry, and ‡Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States
| | - Alexei V Tivanski
- †Department of Chemistry, and ‡Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States
| | - Vicki H Grassian
- †Department of Chemistry, and ‡Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States
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5
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Ray LC, Galand M, Moore LE, Fleshman B. Characterizing the limitations to the coupling between Saturn's ionosphere and middle magnetosphere. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012ja017735] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Mendillo M, Lollo A, Withers P, Matta M, Pätzold M, Tellmann S. Modeling Mars' ionosphere with constraints from same-day observations by Mars Global Surveyor and Mars Express. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011ja016865] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Michael Mendillo
- Department of Astronomy; Boston University; Boston Massachusetts USA
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Anthony Lollo
- Department of Astronomy; Boston University; Boston Massachusetts USA
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Paul Withers
- Department of Astronomy; Boston University; Boston Massachusetts USA
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Majd Matta
- Department of Astronomy; Boston University; Boston Massachusetts USA
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Martin Pätzold
- Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung; University of Cologne; Cologne Germany
| | - Silvia Tellmann
- Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung; University of Cologne; Cologne Germany
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7
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Galand M, Moore L, Mueller-Wodarg I, Mendillo M, Miller S. Response of Saturn's auroral ionosphere to electron precipitation: Electron density, electron temperature, and electrical conductivity. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010ja016412] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Marina Galand
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Luke Moore
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Ingo Mueller-Wodarg
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Michael Mendillo
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Steve Miller
- Atmospheric Physics Laboratory, Department of Physics and Astronomy; University College London; London UK
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De Haan DO, Hawkins LN, Kononenko JA, Turley JJ, Corrigan AL, Tolbert MA, Jimenez JL. Formation of nitrogen-containing oligomers by methylglyoxal and amines in simulated evaporating cloud droplets. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:984-91. [PMID: 21171623 DOI: 10.1021/es102933x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Reactions of methylglyoxal with amino acids, methylamine, and ammonium sulfate can take place in aqueous aerosol and evaporating cloud droplets. These processes are simulated by drying droplets and bulk solutions of these compounds (at low millimolar and 1 M concentrations, respectively) and analyzing the residuals by scanning mobility particle sizing, nuclear magnetic resonance, aerosol mass spectrometry (AMS), and electrospray ionization MS. The results are consistent with imine (but not diimine) formation on a time scale of seconds, followed by the formation of nitrogen-containing oligomers, methylimidazole, and dimethylimidazole products on a time scale of minutes to hours. Measured elemental ratios are consistent with imidazoles and oligomers being major reaction products, while effective aerosol densities suggest extensive reactions take place within minutes. These reactions may be a source of the light-absorbing, nitrogen-containing oligomers observed in urban and biomass-burning aerosol particles.
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Affiliation(s)
- David O De Haan
- Department of Chemistry and Biochemistry, University of San Diego, San Diego, California 92110, United States.
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Moore L, Mueller-Wodarg I, Galand M, Kliore A, Mendillo M. Latitudinal variations in Saturn's ionosphere: Cassini measurements and model comparisons. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2010ja015692] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Luke Moore
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | | | - Marina Galand
- Department of Physics; Imperial College London; London UK
| | - Arvydas Kliore
- Radio Science Systems; Jet Propulsion Laboratory; Pasadena California USA
| | - Michael Mendillo
- Center for Space Physics; Boston University; Boston Massachusetts USA
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10
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Galand M, Moore L, Charnay B, Mueller-Wodarg I, Mendillo M. Solar primary and secondary ionization at Saturn. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008ja013981] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Marina Galand
- Department of Physics; Imperial College London; London UK
| | - Luke Moore
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | | | | | - Michael Mendillo
- Center for Space Physics; Boston University; Boston Massachusetts USA
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11
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Kliore AJ, Nagy AF, Marouf EA, Anabtawi A, Barbinis E, Fleischman DU, Kahan DS. Midlatitude and high-latitude electron density profiles in the ionosphere of Saturn obtained by Cassini radio occultation observations. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008ja013900] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- A. J. Kliore
- Jet Propulsion Laboratory; California Institute of Technology; Pasadena California USA
| | - A. F. Nagy
- Space Physics Research Laboratory; University of Michigan; Ann Arbor Michigan USA
| | - E. A. Marouf
- Department of Electrical Engineering; San Jose State University; San Jose California USA
| | - A. Anabtawi
- Jet Propulsion Laboratory; California Institute of Technology; Pasadena California USA
| | - E. Barbinis
- Jet Propulsion Laboratory; California Institute of Technology; Pasadena California USA
| | - D. U. Fleischman
- Jet Propulsion Laboratory; California Institute of Technology; Pasadena California USA
| | - D. S. Kahan
- Jet Propulsion Laboratory; California Institute of Technology; Pasadena California USA
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