Search Publications
The Dependence of the Circumnuclear Coma Structure on the Properties of the Nucleus
Rodionov, A. V.; Crifo, J. F.
A new step of development of the 3-D circumnuclear coma (“CNC”) model described in Crifoet al.(1995) is presented: now the gas and dust production are computed from an explicit dusty-ice sublimation model and a realistic dust mass spectrum is used. For the first time, (1) a clear distinction is made betweennucleus active area fraction gandactive s…
Injection of large grains into orbits around comet nuclei.
Fulle, M.
Starting from the nucleus surface, the motion of dust boulders of diameters larger than the solar radiation pressure resonance size (Richter & Keller, 1995Icar..114..355R) is investigated by numerical integration of the motion equation for times larger than the comet orbital period. The motion equation takes into account the comet nucleus grav…
Bow shock analysis at comets Halley and Grigg-Skjellerup
Coates, A. J.; Neubauer, F. M.; Mazelle, C.
The interaction of an active comet with the solar wind is effected by the pickup of heavy cometary ions over extended regions of space. It was predicted before any spacecraft encounters with comets that a bow shock would form at a critical point in the mass-loaded flow. Here we present an analysis of the results from Giotto's encounters of comets …
Physical risks of landing on a cometary nucleus
Kührt, E.; Keller, H. U.; Knollenberg, J.
Comets originate from the outer solar system where the density and temperature of the planetary nebula were rather low. They form a distinct class of small solar system bodies and their physical properties differ considerably from those of any other known objects. The present knowledge of the cometary nucleus is cursory and driven more by imaginat…
Compressive character of low frequency waves driven by newborn ions at comet Grigg-Skjellerup
Coates, A. J.; Belmont, G.; Neubauer, F. M. +2 more
The investigation by Giotto of the environment of comet P/Grigg-Skjellerup has provided a large set of observations on cometary low-frequency waves for a weakly active comet, after the observations at comets P/Giacobini-Zinner and P/Halley. A large amount of waves are observed at frequencies close to the local water group ion cyclotron frequencies…
A new look at the nature of comet Halley's LF electromagnetic waves: Giotto observations
Neubauer, Fritz M.; Tsurutani, Bruce T.; Glassmeier, Karl-Heinz +1 more
All of the comet Halley high-time resolution magnetic field data have been examined to determine the nature of the “turbulence” and its difference from that of comets Giacobini-Zinner and Grigg-Skjellerup. Although much of the wave appears unpolarized, occasionally there are intervals of clear order. We find several interesting new wave polarizati…
Comet halley's nucleus: A physical interpretation
Keller, H. U.; Thomas, N.
The nucleus of comet Halley was the first to be detected and observed by cameras on board spacecraft during the fly-bys in 1986. The interpretation of both these observations and of the results from other experiments as well as many subsequent corroborative measurements of comet Halley and of other comets are reviewed. Cometary nuclei are relative…
Observation of interplanetary particles in a corotating interaction region and of energetic water group ions from comet Grigg-Skjellerup
Coates, A. J.; Neubauer, F. M.; Daly, P. W. +2 more
During the flyby of the Giotto S/C with comet Grigg-Skjellerup (G-S) (9-11 July 1992) energetic particles ( EH 2O > 60 keV, Ep > 30 keV, Eα > 3.5 MeV), magnetic fields and plasma ions were measured by three different detectors on board Giotto. The flyby period was characterized by high magnetic field …
Pick-up ions and associated wave energy transport at comet P/Halley: A case study
Neubauer, Fritz M.; Glassmeier, Karl-Heinz; Söding, Anne +1 more
During the flyby of the spacecraft Giotto at comet p/Halley Poynting vectors and Elsässer variables have been determined to study wave propagation directions. The observed wave properties are compared with the theoretically predicted RH-, LH+ and LH- wave modes. Between 10:36 and 19:11 SCET on March 13, 1986 the pr…
Diamagnetic effect of the ion pile-up region of comet halley
Neubauer, F. M.; Israelevich, P. L.; Ershkovich, A. I.
The ion pile-up region in the comet Halley ionosphere observed on the inbound leg of the Giotto trajectory is accompanied by a decrease of the magnetic field strength. This magnetic field dip is explained by means of a diamagnetic effect of the plasma density increase in the pile-up region. No similar magnetic effect of the enhanced plasma density…