| Name: | Shashikiran Ganesh |
| Affiliation: | Physical Research Laboratory |
| Conference ID : | ASI2024_248 |
| Title : | On the negative polarization phenomena in comets |
| Authors : | Shashikiran Ganesh 1, Prithish Halder 2, Goldy Ahuja 1 |
| Authors Affiliation: | 1 Physical Research Laboratory, Navarangpura, Ahmedabad, India
2 Independent Researcher |
| Mode of Presentation: | Oral |
| Abstract Category : | Sun, Solar System, Exoplanets, and Astrobiology |
| Abstract : | Sunlight gets polarized on being scattered by the grains in the coma of a comet. Typically, the polarization is a function of the phase angle at the time of observation and the wavelength of observation and depends on parameters such as the refractive index of the grains and the grain size distribution. At phase angles above 20 degrees, most comets show polarization increasing with phase peaking around 90 to 110 deg and decreasing again. At these phase angles, the polarization is generally positive - i.e., the plane of polarization is perpendicular to the scattering plane. In general, the polarization is higher at longer (redder) wavelengths in the optical regime. At phase angles below ~ 20 deg, the plane of polarization becomes parallel to the plane of scattering, and the observed polarization is said to be negative. Getting observations of comets with phase angles less than 20 deg (and going closer to 0) is quite challenging. So, it is unclear whether the polarization at these phase ranges below 20deg is wavelength-dependent. In this context, we have worked on polarization estimation using light scattering simulations by 'realistic' grains. We have considered dust material with different morphologies represented by a mixture of hierarchical aggregates, ballistic agglomerates, and solids with a combination of silicate and carbonaceous composition. These have been compared with cometary polarimetric observations from the literature. In this contribution, we shall present our results from this work. |
