Observations and analysis of a curved jet in the coma of comet 67P/Churyumov-Gerasimenko

Abstract

Aims. We analyze the physical properties and dynamical origin of a curved jet of comet 67P/Churyumov-Gerasimenko that was observed repeatedly in several nucleus rotations starting on May 30 and persisting until early August, 2015. Methods. We simulated the motion of dust grains ejected from the nucleus surface under the influence of the gravity and viscous drag effect of the expanding gas flow from the rotating nucleus. Results. The formation of the curved jet is a combination of the size of the dust particles (∼0.1−1 mm) and the location of the source region near the nucleus equator. This enhances the spiral feature of the collimated dust stream after the dust is accelerated to a terminal speed on the order of m s −1 .

A New 3D Multi-fluid Dust Model: A Study of the Effects of Activity and Nucleus Rotation on Dust Grain Behavior at Comet 67P/Churyumov–Gerasimenko

“…While it is sufficient to reproduce the gas observations and the larger-scale features of the dust, a more refined activity distribution is required to get the very fine structure. Nevertheless, the agreement between our model and the observations shows that the OSIRIS/WAC image is a better proxy for the column densities and brightness of dust of size from 10 −4 and 10 −5 m, and the curved jet mainly consists of larger dust particles, which is also suggested by Lin et al (2016).…”

Summer fireworks on comet 67P

“…small pit or depression (Belton 2013), and potentially expose fresh volatile material that will continue to sublime. Such mechanism has been discussed for comet 67P in the case of the Imhotep outburst observed in February 2015 (Knollenberg 2015), or the outbursts on 9P/Tempel 1 (Bel-ton et al 2008;Belton 2013). This process, however, requires that the thermal wave (diurnal or seasonal) is able to reach the depth at which ices are available.…”

“…As the OSIRIS cameras were mapping the nucleus with high cadence imaging from July to October 2014, it is unlikely that we have missed an outburst in this period. The next event occurred in February 2015 at a distance of 2.5 AU and is described in Knollenberg (2015). Although much smaller in scale that most of the other events, it is particularly interesting because it arose from an area that had been in the night for 5 hours when the outbursts occurred.…”

“…By chance, most Rosetta instruments were acquiring data at that time and the first results of this common analysis have been presented online shortly after the event (http://blogs.esa.int/rosetta/2015/08/11/cometsfirework-display-ahead-of-perihelion). We modeled the photometric profile of the July 29 event using the approach described in Knollenberg (2015). In short, we convert the radiance over an image area as described above, convert it to a dust cross section, and then to mass assuming a dust size distribution with a power law of -2.6.…”

67P/C-G inner coma dust properties from 2.2 au inbound to 2.0 au outbound to the Sun

“…By analysing the images taken by the OSIRIS camera (Keller et al 2007) on-board Rosetta, Lara et al (2015) reach the conclusion that large-scale dust structures are likely to be due to the contribution of many small features. Jet-like features present in 67P's coma were studied by Lin et al (2016), who concluded that curved jets form as a combination of specific dust particle sizes (0.1−1 mm) and the activity coming from equatorial regions; larger dust particles are accelerated to lower radial velocities than smaller ones. Vincent et al (2015) monitored and modelled the "fuzzy collimated streams of cometary material arising from the nucleus" of 67P, proposing that active cliffs are their main source.…”