Plasma environment around comet 67P/Churyumov–Gerasimenko at Perihelion: model comparsion with Rosetta data

Madanian, H.; Cravens, T. E.; Burch, J.; Goldstein, R.; Rubin, Martin; Nemeth, Z.; Goetz, C.; Koenders, C.; Altwegg, Kathrin (2017). Plasma environment around comet 67P/Churyumov–Gerasimenko at Perihelion: model comparsion with Rosetta data. The astronomical journal, 153(1), p. 30. American Astronomical Society 10.3847/1538-3881/153/1/30

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The plasma environment near comet 67P/Churyumov–Gerasimenko (67P/CG) is dynamically affected by various factors, including the incident solar wind and outgassing from the nucleus. The Rosetta spacecraft MAGnetometer (MAG) instrument observations near perihelion showed crossing events into a magnetic field-free region at about 170 km from the nucleus in 2015 July at 1.26 au from the Sun. At each crossing, the magnitude of the magnetic field dropped by more than 20 nT to near zero. We compared the Ion and Electron Sensor (IES) electron differential flux energy spectrum inside and outside the crossing boundaries. The IES observations show a modest but consistent drop in electron flux for energies between 40 eV and a few hundred eV at each cavity crossing event. This drop in the electron spectra might be due to the absence or attenuation of solar wind electrons inside the observed diamagnetic regions, which might or might not be a diamagnetic cavity. There is no apparent simple linear correlation between the electron count rate measured by the IES at different energies and the magnitude of the magnetic field, however; at all energies, the highest electron count rates are recorded at the highest magnetic field magnitudes. From model-data comparisons it seems that inside diamagnetic regions, pure coma photoelectrons are not sufficient to explain the observations and that a trapping mechanism and/or infused solar wind electrons are necessary to explain the observed electron fluxes.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute

UniBE Contributor:

Rubin, Martin and Altwegg, Kathrin

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering
500 Science > 530 Physics

ISSN:

0004-6256

Publisher:

American Astronomical Society

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

20 Nov 2017 09:49

Last Modified:

20 Nov 2017 09:49

Publisher DOI:

10.3847/1538-3881/153/1/30

BORIS DOI:

10.7892/boris.105770

URI:

https://boris.unibe.ch/id/eprint/105770

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