Practical relations for assessments of the gas coma parameters

Захаров, Владимир; Родионов, А. В.; Fulle, M.; Ivanovski, S.; Bykov, N. Y.; Corte, Vincenzo Della; Rotundi, A.

doi:10.1016/j.icarus.2020.114091

Cited by 14 publications

(12 citation statements)

References 13 publications

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“…In summary, the model computes the thermal emission of an ensemble of particles defined by its size distribution, which is described by a power law n(a) ∝ a α , where α is the size index and the particle radius takes values from a min to a max . The maximum size that can be lifted from the surface of the nucleus of 29P is estimated to be a max = 250 µm, for a CO-driven activity restricted to a cone with a half-angle of 45 • and a total CO production rate of 4 × 10 28 s −1 and a 30 km radius nucleus (Zakharov et al 2018(Zakharov et al , 2021. The wavelength-dependent absorption coefficient and temperature of the dust particles was computed as a function of grain size using the Mie theory combined with an effective medium theory in order to consider mixtures of different materials following Bockelée-Morvan et al ( 2017) (see also Appendix C.2).…”

Section: Dust Production Ratementioning

confidence: 99%

Water, hydrogen cyanide, carbon monoxide, and dust production from distant comet 29P/Schwassmann-Wachmann 1

Bockelée‐Morvan¹,

Biver²,

Schambeau³

et al. 2022

A&A

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Context. 29P/Schwassmann-Wachmann 1 is a distant Centaur/comet, showing persistent CO-driven activity and frequent outbursts. Aims. We aim to better characterize its gas and dust activity from multiwavelength observations performed during outbursting and quiescent states. Methods. We used the HIFI, PACS and SPIRE instruments of the Herschel space observatory on several dates in 2010, 2011, and 2013 to observe the H2O 557 GHz and NH3 573 GHz lines and to image the dust coma in the far-infrared. Observations with the IRAM 30 m telescope were undertaken in 2007, 2010, 2011, and 2021 to monitor the CO production rate through the 230 GHz line, and to search for HCN at 89 GHz. The 70 and 160 µm PACS images were used to measure the thermal flux from the nucleus and the dust coma. Modeling was performed to constrain the size of the sublimating icy grains and to derive the dust production rate. Results. HCN is detected for the first time in comet 29P (at 5σ in the line area). H2O is detected as well, but not NH3. H2O and HCN line shapes differ strongly from the CO line shape, indicating that these two species are released from icy grains. CO production rates are in the range (2.9–5.6) × 1028 s−1 (1400–2600 kg s−1). A correlation between the CO production rate and coma brightness is observed, as is a correlation between CO and H2O production. The correlation obtained between the excess of CO production and excess of dust brightness with respect to the quiescent state is similar to that established for the continuous activity of comet Hale-Bopp. The measured Q(H2O)/Q(CO) and Q(HCN)/Q(CO) production rate ratios are 10.0 ± 1.5 % and 0.12 ± 0.03 %, respectively, averaging the April-May 2010 measurements (Q(H2O) = (4.1 ± 0.6) × 1027 s−1, Q(HCN) = (4.8 ± 1.1) × 1025 s−1). We derive three independent and similar values of the effective radius of the nucleus, ~31 ± 3 km, suggesting an approximately spherical shape. The inferred dust mass-loss rates during quiescent phases are in the range 30–120 kg s−1, indicating a dust-to-gas mass ratio <0.1 during quiescent activity. We conclude that strong local heterogeneities exist on the surface of 29P, with quenched dust activity from most of the surface, but not in outbursting regions. Conclusions. The volatile composition of the atmosphere of 29P strongly differs from that of comets observed within 3 au from the Sun. The observed correlation between CO, H2O and dust activity may provide important constraints for the outburst-triggering mechanism.

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Section: Dust Production Ratementioning

confidence: 99%

Water, hydrogen cyanide, carbon monoxide, and dust production from distant comet 29P/Schwassmann-Wachmann 1

Bockelée‐Morvan¹,

Biver²,

Schambeau³

et al. 2022

A&A

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“…It is assumed that the Knudsen layer is thin and the gas achieves the sonic velocity in the immediate vicinity of the surface. The gas distribution in the coma is taken from Zakharov et al (2021). Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In the early stages of operational planning of a cometary mission, the assessment of coma parameters do not have to be very precise numerically, but should keep the main trends of the processes in the coma. Therefore, we use a simplified model of the gas environment (Zakharov et al, 2021), which is based on integral characteristics of the coma and asymptotic behavior of gas motion.…”

Section: Introductionmentioning

confidence: 99%

On the similarity of dust flows in the inner coma of comets

Захаров

Rotundi

Corte

et al. 2021

Icarus

Self Cite

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“…This velocity field must be defined as a function of time or comet heliocentric distance and as a function of size. Those functions can be taken from the results of complex hydrodynamical calculations used to describe the inner coma (see, e.g., [51][52][53][54] and references therein). The only available in-situ measurements of particle velocities in a cometary coma are those provided by the GIADA and OSIRIS instruments on Rosetta [17,55].…”

Section: Particle Ejection Velocitiesmentioning

confidence: 99%

Monte Carlo Models of Comet Dust Tails Observed from the Ground

Moreno

2022

Universe

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Dust particles leaving the comet nucleus surface are entrained by the gas within the first few nuclear radius distances and are subjected to a complex hydrodynamical environment. From distances of about 20 nuclear radii outwards, the particles decouple from the accelerating gas and are mainly affected by solar gravity and radiation pressure for small-sized nuclei. Their motion is then a function of their so-called β parameter, which is the ratio of the radiation pressure force to gravity force, and their velocity when the gas drag vanishes. At a given observation time, the position of those particles projected on the sky plane form the coma, tail and trail structures that can be observed from ground-based or space-borne instrumentation. Monte Carlo models, based on the computer simulation of the Keplerian trajectories of a large set of dust particles, provide the best possible approach to extract the dust environment parameters from the observed scattered solar light or thermal emission. In this paper, we describe the Monte Carlo code along with some successful applications of such technique to a number of targets.

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Practical relations for assessments of the gas coma parameters

Cited by 14 publications

References 13 publications

Water, hydrogen cyanide, carbon monoxide, and dust production from distant comet 29P/Schwassmann-Wachmann 1

Water, hydrogen cyanide, carbon monoxide, and dust production from distant comet 29P/Schwassmann-Wachmann 1

On the similarity of dust flows in the inner coma of comets

Monte Carlo Models of Comet Dust Tails Observed from the Ground

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