[Previous] | [Session 30P] | [Next]
C. J. Braak, J. F. de Haan, J. W. Hovenier (Free University, Amsterdam), L. D. Travis (NASA Goddard Institute for Space Studies, New York)
Some photopolarimetric observations of various areas on the Jovian disk, made by the Galileo Photopolarimeter/Radiometer experiment during the G8 orbit, are presented. These observations involve the brightness and linear polarization of the reflected sunlight at wavelengths of 678 and 945 nm, and phase angles between 40 and 110 degrees.
A first inspection of the data revealed two striking aspects: 1) Very high polarization (up to 70 per cent) in the South Polar Region (SPR) at phase angles near 69 and 102 degrees and at both wavelengths. 2) Several instances (both in the SPR and the Great Red Spot) of phase angles at which the degree of linear polarization vanishes.
The observed brightness and high linear polarization in the SPR are discussed in terms of simple atmospheric models, involving scattering by molecules and particles above a reflecting surface. The multiple light scattering is modeled with the adding/doubling method, taking polarization and all orders of scattering into account. Assuming spherical particles, an upper limit on the size of particles above the main cloud deck is derived.
The author(s) of this abstract have provided an email address for comments about the abstract: rbraak@nat.vu.nl