We study the effect of lightning on the lower ionosphere of Saturn. A self-consistent one-dimensional model of the electric field and electron density is used to estimate the changes of the local electron and photon emissions. The chemical fingerprint and ion densities are determined using a detailed self-consistent kinetic model. Charge moment change, depth of lightning flashes and their duration are estimated based on the known constraints of saturnian lightning activity. We test two electron density profiles and find that the conservative estimation of lightning charge moment change 104 to 105Ckm could lead to faint halos and possibly sprites if the base of the ionosphere is located at 1000km above the 1bar level; if the base of the ionosphere is located at 600km then only the extreme scenario of a 106Ckm charge moment change could induce considerable ionization, halos and possibly sprites. We found that H3+ ions are rapidly produced from the parent H2+ ions through the fast reaction H2++H2→H3++H, so that H3+ becomes the dominant ion in all the scenarios considered. The resulting light emissions, mostly in the blue and ultraviolet spectral regions, are below the detection threshold of Cassini.
Bibliographical noteFunding Information:
The work of DD and YY is supported by the Israeli Ministry of Science scholarship in Memory of Col. Ilan Ramon, the Research Authority of the Open University of Israel, and by the Israeli Science Foundation Grant 117/09 . Cooperation was facilitated by the support of the European Science Foundation , Grant No. 5269 . The work by AL, FJGV and FCPR is supported by the Spanish Ministry of Science and Innovation , MINECO under project AYA2011-29936-C05-02 and by the Junta de Andalucia under Proyecto de Excelencia FQM-5965. AL is supported by a Ramón y Cajal contract, Code RYC-2011-07801 and FCPR acknowledges MINECO for a FPI Grant, Code BES-2010-042367 .
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