Cloud and haze activity at Jupiter’s polar regions and zone-belt structure investigated from multispectral and polarimetric observations

Abstract:

Polarimetric observation is an efficient method for determining the particle properties of the planet's surface and atmosphere. We can obtain the information of atmospheric particle properties with model calculations. Previous studies have revealed the latitudinal distribution of polarization, considered to be the effects of zone-belt structure and polar haze [McLean et al., 2017, Schmid et al., 2011]. For spectral imaging observations, methane absorption wavelength has sensitivity at specific altitudes from the upper troposphere to the stratosphere due to the optical path difference of the reflected light [Karkoschka et al., 1994. Previous observations have only conducted only a few times a year, and the time variability of particle properties near the Jovian tropopause, related with the spatiotemporal changing of clouds, has not been fully discussed. The purpose of our study is to observe the motion of the polar upper layer in the Jovian atmosphere and the time variations of the particle characteristics from the polarimetric and multispectral imaging using the 1.6 m Pirka telescope owned by Hokkaido Univ and to investigate the convection mechanism of the Jovian atmosphere by comparing with the multispectral imaging data to polarimetric imaging data.

In this presentation, we introduce the observation results from May 2019 to July 2020 using the Multi Spectral Imager (MSI) (pixel scale = 0.39 "/ pix) with the band-pass filters of 619 nm, 727 nm, 756 nm, and 889 nm, which is mounted on the Pirka telescope. The deepest methane absorption wavelength (889 nm) images shows the strongest polarization at the polar region and strong latitudinal dependence consistent with the results of Schmid et al.,[2011]. There is a correlation between the polarization and the flux intensity corrected for peripheral attenuation in the 727 nm and 889 nm imaging. This relationship is strong in the latitudinal direction corresponding to the zone-belt structure and seen in the longitude direction considered to be reflected by the variations in cloud top height and particle composition. From continuous observations on 29-31 May, no significant temporal variation of polarization with respect to the cloud structure was seen. At the presentation, we’ll show the initial results and the future observation plan more in detail.