Electron dynamics near diamagnetic regions of comet 67P/Churyumov- Gerasimenko

Madanian, H.; Burch, J.L.; Eriksson, A.I.; Cravens, T.E.; Galand, M.; Vigren, E.; Goldstein, R.; Nemeth, Z.; Mokashi, P.; Richter, I.; Rubin, M. (2020). Electron dynamics near diamagnetic regions of comet 67P/Churyumov- Gerasimenko. Planetary and space science, 187, p. 104924. Elsevier 10.1016/j.pss.2020.104924

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The Rosetta spacecraft detected transient and sporadic diamagnetic regions around comet 67P/Churyumov-Ger- asimenko. In this paper we present a statistical analysis of bulk and suprathermal electron dynamics, as well as a case study of suprathermal electron pitch angle distributions (PADs) near a diamagnetic region. Bulk electron densities are correlated with the local neutral density and we find a distinct enhancement in electron densities measured over the southern latitudes of the comet. Flux of suprathermal electrons with energies between tens of eV to a couple of hundred eV decreases each time the spacecraft enters a diamagnetic region. We propose a mechanism in which this reduction can be explained by solar wind electrons that are tied to the magnetic field and after having been transported adiabatically in a decaying magnetic field environment, have limited access to the diamagnetic regions. Our analysis shows that suprathermal electron PADs evolve from an almost isotropic outside the diamagnetic cavity to a field-aligned distribution near the boundary. Electron transport becomes chaotic and non-adiabatic when electron gyroradius becomes comparable to the size of the magnetic field line curvature, which determines the upper energy limit of the flux variation. This study is based on Rosetta obser- vations at around 200 km cometocentric distance when the comet was at 1.24 AU from the Sun and during the southern summer cometary season.

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

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering

ISSN:

0032-0633

Publisher:

Elsevier

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

04 Nov 2020 16:44

Last Modified:

26 Feb 2021 14:30

Publisher DOI:

10.1016/j.pss.2020.104924

ArXiv ID:

2007.05827

BORIS DOI:

10.7892/boris.147339

URI:

https://boris.unibe.ch/id/eprint/147339

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