First results from the Giotto magnetometer experiment at comet Halley

Neubauer, F. M.; Glaßmeier, Karl‐Heinz; Pohl, M.; Raeder, J.; Acuña, M. H.; Burlaga, L. F.; Ness, N. F.; Musmann, G.; Mariani, F.; Wallis, M. K.; Ungstrup, E.; Schmidt, H. U.

doi:10.1038/321352a0

Cited by 345 publications

(154 citation statements)

References 10 publications

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“…Theoretical discussions of the selfconsistent excitation of waves were given in Wu & Alfven Davidson (1972), Winske et al (1985), Gary et al (1986), and many other subsequent authors (see review articles by Wu 1991 andBrinca 1991). The prediction was veriÐed by in situ observations with ICE and other spacecraft (Tsurutani & Smith 1985a, 1985bNeubauer et al 1986 ;Saito et al 1986 ;Smith et al 1986 ;. On the other hand, enhanced waves Alfven intrinsic to the solar wind are well known (Belcher & Davis 1971 ;Denskat, Beinroth, & Neubauer 1983).…”

Section: Ion Pickup Via W Aves Alfvenmentioning

confidence: 93%

A Source of Energetic Particles Associated with Solar Flares

Wang

et al. 2001

ApJ

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Energetic particles produced at a solar Ñare event are an issue of great theoretical interest. A scenario involving magnetic Ðeld reconnection and newborn ions produced by ionization of neutral atoms in the lower corona is proposed by Wu. A series of two-dimensional hybrid simulations has been carried out to investigate this scenario further, and the results are presented in this paper. It is shown that under certain conditions the proposed process can produce protons with energies in the range of 10È100 MeV with a timescale of 10~4 to 10~3 s in a reconnection layer via the so-called ion pickup process. The acceleration process is sensitive to the ambient magnetic Ðeld. The maximum energy attainable is also discussed in terms of altitudes above the photosphere on the basis of a certain magnetic Ðeld model.

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Section: Ion Pickup Via W Aves Alfvenmentioning

confidence: 93%

A Source of Energetic Particles Associated with Solar Flares

Wang

et al. 2001

ApJ

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“…In this article, we will relay mainly on data from the Giotto magnetometer MAG provided by Neubauer et al [1993] and the Implanted Ion Sensor of the JPA experiment provided by Johnstone et al [1993].…”

Section: Results and Comparison With The Giotto's Observationsmentioning

confidence: 99%

“…These parameters were compiled from the work of Johnstone et al [1993], Neubauer et al [1993], Johnstone [1995], Coates et al [1997] and Lebedev [2000] and are summarized in Table 1. We assume in this model that these conditions were stationary during the comet flyby.…”

Section: Physical Modelmentioning

confidence: 99%

“…Comparison between the measured (solid line) [Neubauer et al, 1993] and modeled magnetic field magnitude (dashed line). 1.3 1.9 Gas production rate at perihelion, a s À1 6.7 -7.5 Â 10 27 4 -7.5 Â 10 27 a The production rate for comet GS is derived from Giotto data during the 1992 flyby [Johnstone et al, 1993;Neubauer et al, 1993] whereas the production rate for comet CG is a prediction for the 2015 perihelion passage provided by Kossacki and Szutowicz [2006]. from the inner coma totaly controlled by the outflowing cometary gas is very small due to the solar wind conditions of Table 1.…”

Section: Extrapolation To Comet 67p/churyumovgerasimenkomentioning

confidence: 99%

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New multi‐fluid MHD model of comet 26P/Grigg‐Skjellerup: Extrapolation to comet 67P/Churyumov‐Gerasimenko

Benna

Mahaffy

2006

Geophysical Research Letters

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[1] The Multi-fluid MHD simulator CASIM3D models the atmosphere of comet 26P/Grigg-Skjellerup as it was seen by the Giotto spacecraft during its flyby of the comet in July 1992. CASIM3D integrates the major chemical reactions and physical interactions to compute self-consistently over an adaptive Cartesian mesh the dynamics of ions, electrons, and neutrals within the coma. Using this model, we derived water ion velocity and density profiles and magnetic field strength along the Giotto path that are in good agreement with the recorded observations. This model is also extrapolated to the case of 67P/Churyumov-Gerasimenko for its perihelion passage of 2015 to provide a preliminary assessment of the structure of the coma of this comet. We show that the inner boundary layers are just few dozen kilometers large. This could provide an additional constraint to the orbit of the spacecraft Rosetta to maximize the science return of the mission. Citation: Benna, M., and P. R.

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“…As the outgassing rate increases, a contact surface forms (e.g., Schmidt & Wegmann 1982;Neubauer et al 1986) and the solar wind plasma and magnetic field no longer have access to the nucleus. Inside the contact surface, cometary neutrals and ions propagate radially away from the nucleus until they arrive at the boundary.…”

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confidence: 99%

ROSINA/DFMS and IES observations of 67P: Ion-neutral chemistry in the coma of a weakly outgassing comet

Fuselier

Altwegg

Balsiger

et al. 2015

A&A

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Context. The Rosetta encounter with comet 67P/Churyumov-Gerasimenko provides a unique opportunity for an in situ, up-close investigation of ion-neutral chemistry in the coma of a weakly outgassing comet far from the Sun. Aims. Observations of primary and secondary ions and modeling are used to investigate the role of ion-neutral chemistry within the thin coma. Methods. Observations from late October through mid-December 2014 show the continuous presence of the solar wind 30 km from the comet nucleus. These and other observations indicate that there is no contact surface and the solar wind has direct access to the nucleus. On several occasions during this time period, the Rosetta/ROSINA/Double Focusing Mass Spectrometer measured the low-energy ion composition in the coma. Organic volatiles and water group ions and their breakup products (masses 14 through 19), CO + , and CO + 2 (masses 28 and 44) and other mass peaks (at masses 26, 27, and possibly 30) were observed. Secondary ions include H 3 O + and HCO + (masses 19 and 29). These secondary ions indicate ion-neutral chemistry in the thin coma of the comet. A relatively simple model is constructed to account for the low H 3 O + /H 2 O + and HCO + /CO + ratios observed in a water dominated coma. Results from this simple model are compared with results from models that include a more detailed chemical reaction network. Results. At low outgassing rates, predictions from the simple model agree with observations and with results from more complex models that include much more chemistry. At higher outgassing rates, the ion-neutral chemistry is still limited and high HCO + /CO + ratios are predicted and observed. However, at higher outgassing rates, the model predicts high H 3 O + /H 2 O + ratios and the observed ratios are often low. These low ratios may be the result of the highly heterogeneous nature of the coma, where CO and CO 2 number densities can exceed that of water.

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First results from the Giotto magnetometer experiment at comet Halley

Cited by 345 publications

References 10 publications

A Source of Energetic Particles Associated with Solar Flares

A Source of Energetic Particles Associated with Solar Flares

New multi‐fluid MHD model of comet 26P/Grigg‐Skjellerup: Extrapolation to comet 67P/Churyumov‐Gerasimenko

ROSINA/DFMS and IES observations of 67P: Ion-neutral chemistry in the coma of a weakly outgassing comet

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