Show simple item record

The atmosphere of comet 67P/Churyumov-Gerasimenko diagnosed by charge-exchanged solar wind alpha particles

dc.contributor.authorSimon Wedlund, C.
dc.contributor.authorKallio, E.
dc.contributor.authorAlho, M.
dc.contributor.authorNilsson, H.
dc.contributor.authorStenberg Wieser, G.
dc.contributor.authorGunell, H.
dc.contributor.authorBehar, E.
dc.contributor.authorPusa, J.
dc.contributor.authorGronoff, G.
dc.date2016
dc.date.accessioned2016-04-06T09:49:54Z
dc.date.available2016-04-06T09:49:54Z
dc.identifier.urihttps://orfeo.belnet.be/handle/internal/3339
dc.descriptionContext. The ESA/Rosetta mission has been orbiting comet 67P/Churyumov-Gerasimenko since August 2014, measuring its dayside plasma environment. The ion spectrometer onboard Rosetta has detected two ion populations, one energetic with a solar wind origin (H+, He2+, He+), the other at lower energies with a cometary origin (water group ions such as H2O+). He+ ions arise mainly from charge-exchange between solar wind alpha particles and cometary neutrals such as H2O. Aims. The He+ and He2+ ion fluxes measured by the Rosetta Plasma Consortium Ion Composition Analyser (RPC-ICA) give insight into the composition of the dayside neutral coma, into the importance of charge-exchange processes between the solar wind and cometary neutrals, and into the way these evolve when the comet draws closer to the Sun. Methods. We combine observations by the ion spectrometer RPC-ICA onboard Rosetta with calculations from an analytical model based on a collisionless neutral Haser atmosphere and nearly undisturbed solar wind conditions. Results. Equivalent neutral outgassing rates Q can be derived using the observed RPC-ICA He+/He2+ particle flux ratios as input into the analytical model in inverse mode. A revised dependence of Q on heliocentric distance Rh in AU is found to be Rh -7.06Rh-7.06 between 1.8 and 3.3 AU, suggesting that the activity in 2015 differed from that of the 2008 perihelion passage. Conversely, using an outgassing rate determined from optical remote sensing measurements from Earth, the forward analytical model results are in relatively good agreement with the measured RPC-ICA flux ratios. Modelled ratios in a 2D spherically-symmetric plane are also presented, showing that charge exchange is most efficient with solar wind protons. Detailed cometocentric profiles of these ratios are also presented. Conclusions. In conclusion, we show that, with the help of a simple analytical model of charge-exchange processes, a mass-capable ion spectrometer such as RPC-ICA can be used as a "remote-sensing" instrument for the neutral cometary atmosphere. © 2016 ESO.
dc.languageeng
dc.titleThe atmosphere of comet 67P/Churyumov-Gerasimenko diagnosed by charge-exchanged solar wind alpha particles
dc.typeArticle
dc.subject.frascatiPhysical sciences
dc.audienceScientific
dc.subject.freeAlpha particles
dc.subject.freeCharge transfer
dc.subject.freeInverse problems
dc.subject.freeIon exchange
dc.subject.freeIons
dc.subject.freeOrbits
dc.subject.freeParticle spectrometers
dc.subject.freeRemote sensing
dc.subject.freeSolar wind
dc.subject.freeSpectrometers
dc.subject.free67p/churyumov-gerasimenko
dc.subject.freeCharge exchange process
dc.subject.freeComets: general
dc.subject.freeComets: individual: 67P/Churyumov-Gerasimenko
dc.subject.freeHeliocentric distances
dc.subject.freeInstrumentation: detectors
dc.subject.freeMethods:analytical
dc.subject.freeOptical remote sensing
dc.subject.freeAnalytical models
dc.source.titleAstronomy and Astrophysics
dc.source.volume587
dc.source.pageA154
Orfeo.peerreviewedYes
dc.identifier.doi10.1051/0004-6361/201527532
dc.identifier.scopus2-s2.0-84960532707


Files in this item

Thumbnail
Name:
SimonWedlund(2016).pdf
Size:
4.252Mb
Format:
PDF
View/Open

This item appears in the following Collection(s)

Show simple item record