Rotational Disruption of Nonspherical Cometary Dust Particles by Radiative Torques

Herranen, Joonas

doi:10.3847/1538-4357/ab8009

Cited by 9 publications

(6 citation statements)

References 39 publications

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“…Fluffy dust particles with a tensile strength of <10 5 N m −2 (Mendis 1991) and a high charge-to-mass ratio (Fulle et al 2015) are more vulnerable to disintegration due to either electrostatic fragmentation, ice sublimation and/or radiative torques (Herranen 2020) than low porosity dust. In the end, the high ratio of fluffy versus compact dust particles naturally leads to an increase in the small ( µm-sized) particles in the size distribution of the coma dust as it moves out from the nucleus.…”

Section: Resultsmentioning

confidence: 99%

An Update of the Correlation between Polarimetric and Thermal Properties of Cometary Dust

Kwon,

Kolokolova,

Agarwal

et al. 2021

Preprint

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Context. Comets are conglomerates of ice and dust particles, the latter of which encode information on changes in the radiative and thermal environments to date. Dust displays distinctive scattered and thermal radiation in the visible and mid-infrared (MIR) wavelengths, respectively, based on its inherent characteristics. Aims. We aim to identify a possible correlation between the properties of scattered and thermal radiation from dust and the principal dust characteristics responsible for this relationship, and therefrom to gain insights into comet evolution. Methods. We use the NASA/PDS archival polarimetric data on cometary dust in the Red (0.62-0.73 µm) and K (2.00-2.39 µm) domains to leverage the relative excess of the polarisation degree of a comet to the average trend at the given phase angle (P excess ) as a metric of the dust's scattered light characteristics. The flux excess of silicate emissions to the continuum around 10 µm (F Si /F cont ) is adopted from previous studies as a metric of the dust's MIR feature.Results. The two observables -P excess and F Si /F cont -show a positive correlation when P excess is measured in the K domain (Spearman's rank correlation coefficient ρ = 0.71 +0.10 −0.19 ). No significant correlation was identified in the Red domain (ρ = 0.13 +0.16 −0.15 ). The gas-rich comets have systematically weaker F Si /F cont than the dust-rich ones, yet both groups retain the same overall tendency with different slope values. Conclusions. The observed positive correlation between the two metrics indicates that composition is a peripheral factor in characterising the dust's polarimetric and silicate emission properties. The systematic difference in F Si /F cont for gas-rich versus dust-rich comets would rather correspond with the difference in their dust size distribution. Hence, our results suggest that the current MIR spectral models of cometary dust, which search for a minimum χ 2 fit by considering various dust properties simultaneously, should prioritise the dust size and porosity over the composition. With light scattering being sensitive to different size scales in two wavebands, we expect the K-domain polarimetry to be sensitive to the properties of dust aggregates, such as size and porosity, which might have been influenced by evolutionary processes. On the other hand, the Red-domain polarimetry reflects the characteristics of sub-µm constituents in the aggregate.

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Section: Resultsmentioning

confidence: 99%

An Update of the Correlation between Polarimetric and Thermal Properties of Cometary Dust

Kwon,

Kolokolova,

Agarwal

et al. 2021

Preprint

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“… 2016 ) and thus are sensitive to fragmentation and erosion mechanisms such as electrostatic repulsion (e.g. Hill and Mendis 1981 ) and the centrifugal force from increasing rotation speed of dust grains due to direct solar radiation (Herranen 2020 ) or sublimation driven effects (Steckloff and Jacobson 2016 ). Gas spectrometer measurements have shown that some minor species, HF, HCl and HBr, emanate from an extended distributed source.…”

Section: Plasmamentioning

confidence: 99%

The Plasma Environment of Comet 67P/Churyumov-Gerasimenko

et al. 2022

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The environment of a comet is a fascinating and unique laboratory to study plasma processes and the formation of structures such as shocks and discontinuities from electron scales to ion scales and above. The European Space Agency’s Rosetta mission collected data for more than two years, from the rendezvous with comet 67P/Churyumov-Gerasimenko in August 2014 until the final touch-down of the spacecraft end of September 2016. This escort phase spanned a large arc of the comet’s orbit around the Sun, including its perihelion and corresponding to heliocentric distances between 3.8 AU and 1.24 AU. The length of the active mission together with this span in heliocentric and cometocentric distances make the Rosetta data set unique and much richer than sets obtained with previous cometary probes. Here, we review the results from the Rosetta mission that pertain to the plasma environment. We detail all known sources and losses of the plasma and typical processes within it. The findings from in-situ plasma measurements are complemented by remote observations of emissions from the plasma. Overviews of the methods and instruments used in the study are given as well as a short review of the Rosetta mission. The long duration of the Rosetta mission provides the opportunity to better understand how the importance of these processes changes depending on parameters like the outgassing rate and the solar wind conditions. We discuss how the shape and existence of large scale structures depend on these parameters and how the plasma within different regions of the plasma environment can be characterised. We end with a non-exhaustive list of still open questions, as well as suggestions on how to answer them in the future.

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“…In general, the fraction of grains on high-J attractors, denoted by f high−J , depends on the grain properties (shape, size, and magnetic properties), and 0 < f high−J ≤ 1. Herranen [165] calculated RATs for aggregates and found f high−J ∼ 0.35-1 for aggregate grains. The presence of iron inclusions is found to increase f high−J to unity (Hoang and Lazarian [97]).…”

Section: Relationship Between Rotational Disruption and Grain Alignmentmentioning

confidence: 99%

Rotational Disruption of Astrophysical Dust and Ice—Theory and Applications

Hoang

2020

Galaxies

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Dust is an essential component of the interstellar medium (ISM) and plays an important role in many different astrophysical processes and phenomena. Traditionally, dust grains are known to be destroyed by thermal sublimation, Coulomb explosions, sputtering, and shattering. The first two mechanisms arise from the interaction of dust with intense radiation fields and high-energy photons (extreme UV), which work in a limited astrophysical environment. The present review is focused on a new destruction mechanism present in the dust-radiation interaction that is effective in a wide range of radiation fields and has ubiquitous applications in astrophysics. We first describe this new mechanism of grain destruction, namely rotational disruption induced by Radiative Torques (RATs) or RAdiative Torque Disruption (RATD). We then discuss rotational disruption of nanoparticles by mechanical torques due to supersonic motion of grains relative to the ambient gas, which is termed MEchanical Torque Disruption (METD). These two new mechanisms modify properties of dust and ice (e.g., size distribution and mass), which affects observational properties, including dust extinction, thermal and nonthermal emission, and polarization. We present various applications of the RATD and METD mechanisms for different environments, including the ISM, star-forming regions, astrophysical transients, and surface astrochemistry.

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Rotational Disruption of Nonspherical Cometary Dust Particles by Radiative Torques

Cited by 9 publications

References 39 publications

An Update of the Correlation between Polarimetric and Thermal Properties of Cometary Dust

An Update of the Correlation between Polarimetric and Thermal Properties of Cometary Dust

The Plasma Environment of Comet 67P/Churyumov-Gerasimenko

Rotational Disruption of Astrophysical Dust and Ice—Theory and Applications

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