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Similarities between in situ measurements of local dust light scattering and dust flux impact data within the coma of 1P/Halley
Fulle, M.; Levasseur-Regourd, A. C.; McBride, N. +1 more
In situ measurements of the light locally scattered by cometary dust, as well as the local dust spatial density are only available for one comet, 1P/Halley. These data, returned from the Optical Probe Experiment (OPE) and the Dust Impact Detection System (DIDSY) aboard the European Space Agency spacecraft Giotto, are re-assessed in light of the re…
Numerical simulation of the dust flux on a spacecraft in orbit around an aspherical cometary nucleus - I
Fulle, M.; Rodionov, A. V.; Crifo, J. F.
This study is the first investigation of the dust collection by a spacecraft orbiting a cometary nucleus, which is based on a physically consistent ab-initio model of the dust distribution in the vicinity of an aspherical comet nucleus. The homogeneous bean-shaped nucleus of Crifo & Rodionov (1997a) is used, with updated parameter values adapt…
On the diamagnetic effect associated with the ion pile-up region in the coma 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. Maximum of the plasma pressure seems to coincide with the…
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…
Evidence for two classes of comets from their polarimetric properties at large phase angles.
Levasseur-Regourd, A. C.; Hadamcik, E.; Renard, J. B.
The dependence of the linear polarization of solar light scattered by cometary dust upon the phase angle has been studied, through appropriate fits, from a data base of 22 comets and 750 points (mainly in the green and red spectral domains). Although the whole coma polarization is found to slightly increase with the wavelength, all the data obtain…
The D/H and ^18^O/^16^O ratios in water from comet P/Halley.
Eberhardt, P.; Krankowsky, D.; Hodges, R. R. +1 more
From a detailed evaluation of the ion currents measured by the Neutral Mass Spectrometer (NMS) on the Giotto spaceprobe in the 17.5amu/e to 21.5amu/e mass range inside the contact surface of P/Halley we derive the cometary ion densities for masses 18amu/e to 21amu/e. From these we calculate the deuterium and ^18^O abundances in the H_3_O^+^ ion to…
Gas and dust emission from a dusty porous comet.
Capaccioni, F.; Orosei, R.; Coradini, A. +5 more
A comet nucleus is a porous aggregate of ices and dust in which solar heating causes the sublimation of volatiles and the ejection of dust particles lifted by the flow of the escaping gases. We present a numerical model that solves the heat conduction and the gas diffusion equations throughout a porous comet nucleus made of H_2_O ice, CO_2_ ice an…
The electron temperature in the inner coma of comet P/Halley.
Eberhardt, P.; Krankowsky, D.
From the CH_3_OH_2_^+^/H_3_O^+^ and H_3_O^+^/H_2_O^+^ ratios measured by the Giotto Neutral Mass Spectrometer in the inner coma (distance <20000km) of comet P/Halley we derive two independent electron temperature profiles. They agree very well and the electron temperature T_e_ increases gradually from =~100K at 2000km to =~900K at 8500km follow…
The sensitivity of the size distribution to the grain dynamics: simulation of the dust flux measured by GIOTTO at P/Halley.
Fulle, M.; Mennella, V.; Colangeli, L. +2 more
A cometary dust emission model, based on rigorous keplerian dynamics, is developed and, for the first time, the dependence of fluence on the probability distribution of the dust ejection velocity vector is demonstrated. The results are compared with the fluences measured by the DIDSY experiment on board the GIOTTO spacecraft during the Halley's fl…
Physics and chemistry of ions in the pile-up region of comet P/Halley.
Altwegg, K.; Balsiger, H.; Geiss, J. +1 more
Measurements by the mass spectrometers onboard Giotto during the flyby at comet P/Halley showed a steep increase in the ion density outside the diamagnetic cavity at a distance of about 8000km from the nucleus (Balsiger et al. 1986a; Krankowsky et al. 1986). The maximum ion density was observed at a distance of 12000km from the nucleus rather than…