Radar backscattering from a large-grain cometary coma: numerical simulation

We measured the degree of linear polarization of Comet C/2020 S3 (Erasmus) on November 13, 20, 22, and 23, 2020, while the comet was observed at large phase angles, α = 62.6° – 66.6°. On the first two epochs, the polarization closely matched what was previously observed in Comet C/1989×1 (Austin). On the third epoch, the polarization was found to rise slightly, and on the latest epoch, it rose significantly, exceeding that of Comet Austin. On the last observation, the polarization of Comet Erasmus appears to be more consistent with what was previously seen in Comet C/1996 B2 (Hyakutake) at a similar phase angle. While such short-term transient behavior has been seen previously, Comets Austin and Hyakutake belong to two different classes in classifications based on the amplitude of their positive polarization Pmax and, hence, Comet Erasmus revealed a transition from the class of low Pmax comets to that of high Pmax comets within only a few days. Polarization images and modeling suggest that the transition occurred due to a decrease in the relative abundance of Mg-rich silicate particles in the inner coma by 1/3, revealing a qualitative change in emanations of dust particles from the Erasmus nucleus.

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On the Small Contribution of Supermicron Dust Particles to Light Scattering by Comets

Zubko

Videen

Arnold

et al. 2020

ApJ

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We quantitatively investigate the contribution of large dust particles to the polarimetric response in comets using the light-scattering properties of model agglomerated debris particles. We demonstrate that large, supermicron-sized particles have a decreasing role on the degree of linear polarization at phase angle α ≤ 80°, and the effect of particles greater than 10 μm is minimal. At larger phase angles, they may only slightly increase the measured percent of polarization by up to 1%. Omitting the effects of these particles in modeling the observations only slightly affects the retrievals of the microphysical properties of dust in comets and could lead to a small underestimation of the index in a power-law size distribution and population of weakly absorbing dust particles.

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Radar backscattering from a large-grain cometary coma: numerical simulation

Cited by 3 publications

References 27 publications

Decimeter-scale particle characterization in the coma of 73P/Schwassmann-Wachmann 3 using dual-wavelength radar observations

Decimeter-scale particle characterization in the coma of 73P/Schwassmann-Wachmann 3 using dual-wavelength radar observations

C/2020 S3 (Erasmus): Comet with a presumably transient maximum of linear polarization Pmax

On the Small Contribution of Supermicron Dust Particles to Light Scattering by Comets

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