Polarimetric studies of comet Levy 1990 XX

The spherical and non-spherical dust-grain characteristics of comet Levy 1990 XX are studied in this paper. Using T-matrix theory, a good theoretical fit to the polarisation data observed by Chernova and co-workers for comet Levy 1990 XX is reported in the present work. The calculated degree of linear polarisation ( p) as a function of observed scattering angle (.) produced by prolate spheroidal crystalline olivine particles with effective radius (r(eff) = 0.218 mu m), effective variance (v(eff) = 0.0036), and aspect ratio (E = 0.486) are compatible with the comet's observed polarisation at lambda = 0.485 mu m. After comparing the above result with the Mie theory result (r(eff) = 0.115 mu m, v(eff) = 0.0465), it is found that prolate grains give the better fit to the observed polarisation data. Also, the negative polarisation behaviour of comet Levy 1990 XX is discussed.