Search Publications
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…
D/H and O-18/O-16 ratio in the hydronium ion and in neutral water from in situ ion measurements in comet Halley
Altwegg, K.; Balsiger, H.; Geiss, J.
The D/H ratio and the O-18/O-16 ratio in hydronium ions in the gas coma of comet Halley have been determined from ion data obtained by the high intensity sensor (HIS) of the ion spectometer (IMS) on board the spacecraft Giotto in 1986. The HIS instrument measured the reliable data for the water group ions over a large distance range from the nucle…
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…
An intercomparison of plasma turbulence at three comets: Grigg-Skjellerup, Giacobini-Zinner, and Halley
Glassmeier, K. -H.; Neubauer, F. M.; Tsurutani, Bruce T.
We examine and intercompare the LF plasma wave turbulence at three comets: Grigg-Skjellerup (GS), Giacobini-Zinner (GZ), and Halley (H). All three have power spectral peaks at the local ion cyclotron frequency (the pump wave) at ∼10-2 Hz, and a power-law fall-off at higher frequencies that suggest the development of turbulent cascades […
Cometary ion pickup processes: Halley and Grigg-Skjellerup compared
Johnstone, A. D.
After Giotto's encounters with two comets of quite different gas production rates we attempt to compare the results to see:- a) to what extent theories which fitted the results at Halley could be applied to the much smaller Grigg-Skjellerup; b) whether the different relationship between the various scale lengths involved created any observable eff…
Comparison of the main magnetic and plasma features in the environments of comets Grigg-Skjellerup and Halley
Glassmeier, K. -H.; Neubauer, F. M.; Reme, H. +1 more
The successful flyby of Giotto at the weakly active comet P/Grigg-Skjellerup on July 10, 1992 has added a new set of observations to those obtained at the active comet P/Halley in March 1986 for the study of the solar wind - comet interaction. Despite the very different scales of the interaction regions for the two comets (10^6 km for Halley and 1…
Interpretation of a glitch observed in the very small dust grain data at halley's comet: (Letter to the Editor)
Kissel, Jochen; Utterback, Nyle G.
In a previous article describing the cloud of attogram dust particles surrounding Comet Halley, the present authors noted a sharp break in the curve of signal amplitude (related to particle size) versus distance to the comet. Arguments were given which supported the explanation that the break was instrumental rather than due to a physical structur…