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U.A. Dyudina, A.P. Ingersoll (Caltech), Galileo SSI Team
We present a study of lightning on Jupiter and the clouds illuminated by the lightning. The Galileo images have a resolution of ~25 km/pixel and are able to resolve the lightning flashes, which have full widths at half maximum in the range 90-160 km (Little et al. 1999). We compare the lightning images with the images produced by our 3D Monte Carlo light scattering model. The main purpose of the study is to learn about the energy, depth, shape, and vertical extent of the lightning and also about the surrounding clouds.
The model calculates Monte Carlo scattering of photons in a 3D opacity distribution. During each scattering light is partially absorbed. The new direction of the photon after scattering is chosen according to the Heney-Greenstain scattering phase function. Images from different directions are produced by accumulating photons flying from the cloud in different solid angles. Lightning is modeled either as a point or a linear light source.
Our results suggest that the observed scattering pattern is produced in a 3D cloud rather than in plane-parallel cloud layer. We will discuss possible shapes and sizes of the lightning and physical mechanisms that may be responsible for the phenomena.
Little,B., et al. Galileo Images of Lightning on Jupiter 1999, Icarus 142,306-323
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