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Models for Polar Haze Formation in Jupiter's Stratosphere

Friedson, A. James and Wong, Ah-San and Yung, Yuk L. (2002) Models for Polar Haze Formation in Jupiter's Stratosphere. Icarus, 158 (2). pp. 389-400. ISSN 0019-1035. doi:10.1006/icar.2002.6885.

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We present coupled chemical–microphysical models for the formation, growth, and physical properties of the jovian polar haze based on a gas-phase photochemical model for the auroral regions developed by A. S. Wong et al. (2000, Astrophys. J.534, L215–217). In this model, auroral particle precipitation provides an important energy source for enhanced decomposition of methane and production of benzene and polycyclic aromatic hydrocarbons (PAHs). We find that at high altitude, A_4 (pyrene, a hydrocarbon consisting of four fused aromatic rings) should homogeneously nucleate to form tiny primary particles. At lower altitudes, A_3 (phenanthrene) and A_2 (naphthalene) heterogeneously nucleate on the A4 nuclei. These particles subsequently grow by additional condensation of A_2 on the nucleated particles and by coagulation and eventually sediment out to the troposphere. We run different cases of the aerosol microphysical model for different assumptions regarding the fractal dimension of aggregate particles formed by the coagulation process. If coagulation is assumed to produce spherical particles (of dimensionality 3), then their mean radius at altitudes below the 20-mbar pressure level is computed to be approximately 0.1 μm. If coagulation produces fractal aggregates of dimension 2.1, then their equivalent mean radius below the 20-mbar level is much larger, of order 0.7 μm. Aggregates with fractal dimensions between 2.1 and 3 form with equivalent mean radii between 0.1 and 0.7 μm. In every case, mean particle radius is found to decrease with increasing altitude, as expected for a system approximately in sedimentation–coagulation equilibrium. The predicted range of altitudes where aerosol formation occurs and the mean size to which particles grow are found to be generally consistent with observations. However, our calculations cannot presently account for the large amount of total aerosol loading inferred by M. G. Tomasko et al. (1986, Icarus65, 218–243). We suggest that the primarily neutral chemical pathway to heavy hydrocarbon and PAH formation proposed by Wong et al. (2000) may proceed too slowly to produce a sufficient amount of condensible material. Inclusion of ion and ion–neutral reactions in the chemical scheme could potentially lead to the prediction of higher PAH production rates, higher nucleation rates, and greater aerosol loading, producing better agreement with the observations.

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Yung, Yuk L.0000-0002-4263-2562
Additional Information:© 2002 Elsevier Science. Received October 9, 2001; Revised April 1, 2002. We thank R. A.West, K. Rages, M. Lemmon, and S. G. Edgington for helpful discussions. We also thank R. G. Gladstone and an anonymous reviewer for their insightful reviews. Many of the calculations were performed on the Cray SV1 supercomputer managed by the Jet Propulsion Laboratory Supercomputing Project. This work was supported by a grant from the NASA Planetary Atmospheres Program. The work was performed by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
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NASA Planetary Atmospheres ProgramUNSPECIFIED
Subject Keywords:Jupiter; atmosphere; photochemistry; aurorae
Issue or Number:2
Record Number:CaltechAUTHORS:20140820-161912639
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Official Citation:Friedson, A. J., Wong, A.-S., & Yung, Y. L. (2002). Models for Polar Haze Formation in Jupiter's Stratosphere. Icarus, 158(2), 389-400. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48752
Deposited By: Joanne McCole
Deposited On:21 Aug 2014 16:52
Last Modified:10 Nov 2021 18:35

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