Ion transport in Titan's upper atmosphere

Based on a combined Cassini data set including Ion Neutral Mass Spectrometer, Radio Plasma Wave Science, and Magnetometer measurements made during nine close encounters of the Cassini spacecraft with Titan, we investigate the electron ( or total ion) distribution in the upper ionosphere of the satellite between 1250 and 1600 km. A comparison of the measured electron distribution with that in diffusive equilibrium suggests global ion escape from Titan with a total ion loss rate of similar to(1.7 +/- 0.4) x 10(25) s(-1). Significant diurnal variation in ion transport is implied by the data, characterized by ion outflow at the dayside and ion inflow at the nightside, especially below similar to 1400 km. This is interpreted as a result of day-to-night ion transport, with a horizontal transport rate estimated to be similar to(1.4 +/- 0.5) x 10(24) s(-1). Such an ion flow is likely to be an important source for Titan's nightside ionosphere, as proposed in Cui et al. [2009a].

[1]  J. Wahlund,et al.  On the ionospheric structure of Titan , 2009 .

[2]  D. Strobel.  Titan's hydrodynamically escaping atmosphere: Escape rates and the structure of the exobase region , 2009 .

[3]  Panayotis Lavvas,et al.  Diurnal variations of Titan's ionosphere , 2009 .

[4]  J. Cui.  Analysis of Titan's neutral upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements in the Closed Source Neutral mode , 2009 .

[5]  J. Fox.  Morphology of the dayside ionosphere of Mars: Implications for ion outflows , 2008 .

[6]  K. Volk,et al.  Distribution and escape of molecular hydrogen in Titan's thermosphere and exosphere , 2008 .

[7]  Roger V. Yelle,et al.  Methane escape from Titan's atmosphere , 2008 .

[8]  S. Asmar,et al.  First results from the Cassini radio occultations of the Titan ionosphere , 2008 .

[9]  W. Ip,et al.  Exospheric heating by pickup ions at Titan , 2008 .

[10]  D. Strobel,et al.  Titan's hydrodynamically escaping atmosphere , 2008 .

[11]  M. Stevens,et al.  Titan airglow spectra from Cassini Ultraviolet Imaging Spectrograph (UVIS): EUV analysis , 2007 .

[12]  P. Canu,et al.  On magnetospheric electron impact ionisation and dynamics in Titan's ram-side and polar ionosphere – a Cassini case study , 2007 .

[13]  Roger V. Yelle,et al.  Ion chemistry and N-containing molecules in Titan's upper atmosphere , 2007 .

[14]  J. Cui,et al.  Horizontal structures and dynamics of Titan's thermosphere , 2007 .

[15]  J. Waite,et al.  The Process of Tholin Formation in Titan's Upper Atmosphere , 2007, Science.

[16]  J. Wahlund,et al.  Electron temperature of Titan's sunlit ionosphere , 2006 .

[17]  David T. Young,et al.  Titan's near magnetotail from magnetic field and electron plasma observations and modeling: Cassini flybys TA, TB, and T3 , 2006 .

[18]  M. Dougherty,et al.  Comparisons between MHD model calculations and observations of Cassini flybys of Titan , 2006 .

[19]  J. H. Waite,et al.  Composition of Titan's ionosphere , 2006 .

[20]  W. Ip,et al.  Titan's ionosphere: Model comparisons with Cassini Ta data , 2005 .

[21]  P. Canu,et al.  Cassini Measurements of Cold Plasma in the Ionosphere of Titan , 2005, Science.

[22]  J. E. Richards,et al.  The Cassini Ion and Neutral Mass Spectrometer (INMS) Investigation , 2004 .

[23]  K.-H. Glassmeier,et al.  The Cassini Magnetic Field Investigation , 2004 .

[24]  Igor V. Sokolov,et al.  Three‐dimensional, multispecies, high spatial resolution MHD studies of the solar wind interaction with Mars , 2004 .

[25]  K. Powell,et al.  The interaction between the magnetosphere of Saturn and Titan's ionosphere , 2001 .

[26]  A. Aylward,et al.  The thermosphere of Titan simulated by a global three‐dimensional time‐dependent model , 2000 .

[27]  Robert W. Schunk,et al.  Ionospheres : physics, plasma physics, and chemistry , 2000 .

[28]  J. Lilensten,et al.  The Ionosphere of Titan: Ideal Diurnal and Nocturnal Cases , 1999 .

[29]  T. Tanaka,et al.  Three-dimensional MHD simulation of the solar wind interaction with the ionosphere of Venus: Results of two-component reacting plasma simulation , 1997 .

[30]  K. Mahajan,et al.  Evidence of upward H+ flow in the Venus dayside ionosphere , 1995 .

[31]  S. Asmar,et al.  Possible Detection of Titan's Ionosphere from Voyager 1 Radio Occultation Observations , 1995 .

[32]  A. Nagy,et al.  The energetics of Titan's ionosphere , 1994 .

[33]  J. Fox,et al.  Evidence for day‐to‐night ion transport at low solar activity in the Venus pre‐dawn ionosphere , 1993 .

[34]  R. Hartle,et al.  Light ion flow in the nightside ionosphere of Venus , 1993 .

[35]  T. Cravens,et al.  Electrons in the ionosphere of Titan , 1992 .

[36]  T. Cravens,et al.  A model of the ionosphere of Titan , 1992 .

[37]  W. Ip.  Titan's Upper Ionosphere , 1990 .

[38]  Jhoon Kim,et al.  Temperatures of individual ion species and heating due to charge exchange in the ionosphere of Venus , 1990 .

[39]  A. Nagy,et al.  A Two-Dimensional Model of the Ionosphere of Venus , 1983 .

[40]  R. Whitten,et al.  The Venus ionosphere at grazing incidence of solar radiation: Transport of plasma to the night ionosphere , 1982 .

[41]  J. Waite,et al.  Model-data comparisons for Titan's nightside ionosphere , 2009 .

[42]  Ronan Modolo,et al.  A global hybrid model for Titan's interaction with the Kronian plasma: Application to the Cassini Ta flyby , 2008 .

[43]  I. Sillanpää,et al.  Hybrid simulation study of ion escape at Titan for different orbital positions , 2006 .