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A kinetic perspective of electron trapping near a weakly outgassing comet
KTH, School of Electrical Engineering and Computer Science (EECS).
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The European Space Agency’s Rosetta spacecraft followed the comet 67P/Churyumov-Gerasimenko from August 2014 to September 2016, providingobservations of the comet ionosphere at varying heliocentric distances. Measurementsfrom the Rosetta mission have shown a multitude of non-thermalelectron distributions in the cometary environment, challenging the previouslyassumed origin and plasma interaction mechanisms near a cometary nucleus.In this thesis, we discuss electron trapping near a weakly outgassing cometfrom a fully kinetic (particle-in-cell) perspective which self consistently describethe ambipolar field. Using electromagnetic fields derived from the simulation,we characterize the trajectories of trapped electrons in the potentialwell surrounding the cometary nucleus and identify the distinguishing featuresin their respective velocity and pitch angle distributions. In accordancewith theoretical findings in space plasma, our analysis allows us to define aclear boundary in velocity phase space between the distributions of trappedand passing electrons.

Abstract [sv]

Europeiska rymdorganisationens rymdsond Rosetta följde mellan augusti 2014och september 2016 kometen 67P/ Churyumov-Gerasimenko och tillhandahöllobservationser av kometens jonosfär på olika heliocentriska avstånd. Mätningarfrån uppdraget har visat en mängd icke-termiska elektron distributioneri kometens miljö och ifrågasatt det tidigare antagandet om ursprung samt plasmainteraktioner nära kometens kärna. I detta arbete undersöker vi elektronfångstnära en svagt utåtgasande komet från ett helt kinetiskt (partikel-i-cell) perspektivvilket på självkonsistent sätt som kan beskriva det ambipolära elektrisktfältet. Genom att använda de elektromagnetiska fälten som härrör frånvår simulering, karakteriserar vi banorna för infångade elektroner i den potentiellabrunnen som omger kometkärnan. Vi identifierar egenskaper frånderas respektive hastighets- och stigvinkelfördelningar. Vår analys som överensstämmermed teoretiska fynd i rymdplasma tillåter oss att definiera entydlig gräns i hastighetsfasutrymme mellan fördelningarna av infångade ochpassande elektroner.

Place, publisher, year, edition, pages
2019. , p. 46
Series
TRITA-EECS-EX ; 2019:416
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-254423OAI: oai:DiVA.org:kth-254423DiVA, id: diva2:1332086
Educational program
Master of Science - Electrophysics
Supervisors
Examiners
Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-08-07Bibliographically approved

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