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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, E04001, doi:10.1029/2007JE002975, 2008

Predictions of the electrical conductivity and charging of the cloud particles in Jupiter's atmosphere

R. C. Whitten

SETI Institute, Mountain View, California, USA


W. J. Borucki

NASA Ames Research Center, Moffett Field, California, USA


K. O'Brien

Department of Physics and Astronomy, Northern Arizona University, Flagstaff, Arizona, USA


S. N. Tripathi

Indian Institute of Technology, Kanpur, India


Abstract

The electrical conductivity and electrical charge on cloud particles (composed of ammonia, ammonium hydrosulfide, and water) in the atmosphere of Jupiter are computed for pressures between 5.5 and 0.1 bars. The source of ionization is galactic cosmic rays (GCR). The distribution of charge among the various reservoirs is a function of altitude and the total area of the aerosol particles. For pressures below 4 bars, the electrons are scavenged efficiently by the cloud particles, decreasing the electron-ion recombination rate and resulting in increased positive ion abundance over that in the absence of the particles. For the upper regions of each cloud layer, the area of the aerosols and the large diffusion rate of the electrons cause most aerosol particles to be negatively charged. Near the bases of the cloud layers, the larger total area of the aerosols causes most of the charge, positive and negative, to reside on particles. Where clouds are present, the reduction of the electron conductivity ranges from a factor of 30 at 0.1 bar to 104 at 4 bars. At pressures near 1 bar and 4 bars, the positive ion conductivity increases by a factor of 10 over that expected for the clear atmosphere. A parametric study of negative ions shows that they are likely to be insignificant. For altitudes below the 0.3-bar level the predicted positive and negative conductivities are well below the detection limit of the relaxation and mutual impedance instruments such as those employed on the Huygens entry probe.

Received 27 July 2007; accepted 27 December 2007; published 1 April 2008.

Keywords: Jupiter clouds; electrical conductivity; cosmic ray ionization.

Index Terms: 6220 Planetary Sciences: Solar System Objects: Jupiter; 5704 Planetary Sciences: Fluid Planets: Atmospheres (0343, 1060); 5719 Planetary Sciences: Fluid Planets: Interactions with particles and fields; 5734 Planetary Sciences: Fluid Planets: Magnetic fields and magnetism.

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Citation: Whitten, R. C., W. J. Borucki, K. O'Brien, and S. N. Tripathi (2008), Predictions of the electrical conductivity and charging of the cloud particles in Jupiter's atmosphere, J. Geophys. Res., 113, E04001, doi:10.1029/2007JE002975.