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Mass loading at 67P/Churyumov-Gerasimenko: A case study
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.ORCID iD: 0000-0003-0177-510X
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Swedish Institute of Space Physics.
Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
Show others and affiliations
2016 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 4, p. 1411-1418Article in journal (Refereed) Published
Abstract [en]

We study the dynamics of the interaction between the solar wind ions and a partially ionized atmosphere around a comet, at a distance of 2.88 AU from the Sun during a period of low nucleus activity. Comparing particle data and magnetic field data for a case study, we highlight the prime role of the solar wind electric field in the cometary ion dynamics. Cometary ion and solar wind proton flow directions evolve in a correlated manner, as expected from the theory of mass loading. We find that the main component of the accelerated cometary ion flow direction is along the antisunward direction and not along the convective electric field direction. This is interpreted as the effect of an antisunward polarization electric field adding up to the solar wind convective electric field.

Place, publisher, year, edition, pages
2016. Vol. 43, no 4, p. 1411-1418
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
URN: urn:nbn:se:ltu:diva-8286DOI: 10.1002/2015GL067436ISI: 000373109000001Scopus ID: 2-s2.0-84975743627Local ID: 6c6ac809-0b7a-4666-8ba3-4712cf4ebf06OAI: oai:DiVA.org:ltu-8286DiVA, id: diva2:981178
Note

Validerad; 2016; Nivå 2; 20160219 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
In thesis
1. Solar Wind Dynamics within The Atmosphere of comet 67P/Churyumov-Gerasimenko
Open this publication in new window or tab >>Solar Wind Dynamics within The Atmosphere of comet 67P/Churyumov-Gerasimenko
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, we explore the dynamics of the solar wind as it perme-ates and flows through a tenuous cometary atmosphere, with a focuson the interaction observed at comet 67P/Churyumov–Gerasimenko.

Seven comets had already been visited by nine different probes when the European spacecraft Rosetta reached comet Churyumov–Gerasimenko in August 2014. The mission was however the first to orbit its host comet, which it did for a total duration of more than two years, corre-sponding to a large part of the comet’s orbit around the Sun. This en-abled to study how the dynamics of the plasma environment evolvedas the comet itself was transformed from one of the smallest obstaclesto the solar wind in the Solar System when far away from the Sun, toa well-established magnetosphere at perihelion.

Most of our efforts tackle the early part of this transformation, when the creation of new-born cometary ions starts to induce significant disturbances to the incident flow. During this stage, a kinetic descrip-tion of the interaction is necessary, as the system of interest cannot be reduced to a hydrodynamic problem. This contrasts with the situation closer to the Sun, where a fluid treatment can be used, at Churyumov–Gerasimenko as well as at previously visited comets.

Rosetta was not a mission dedicated to plasma studies, however. It directly translates into a limited spatial coverage of the cometary plasma environment, which by its nature extends over several spatial scales. An approach solely based on the analysis of in-situ data cannot properly address the major questions on the nature and physics of the plasma environment of Churyumov–Gerasimenko. This thesis there-fore largely exploits the experimental–analytical–numerical triad of approaches. In Chapters 3 and 4 we propose simple models of the ion dynamics and of the cometary plasma environment, and these are tested against experimental and numerical data. Used together,they give a global description of the solar wind ion dynamics through the cometary atmosphere, that we explore in the 2-dimensional and 3-dimensional cases (Chapter 5). In Chapter 6, we propose a view onthe interaction and its fluid aspects when closer to the Sun.

Abstract [sv]

I  denna  avhandling  undersöks  solvindens  dynamik  när  den  flödar genom  en  tunn  kometatmosfär,  med  fokus  på  den  interaktion  somobserverats vid kometen 67P/Churyumov-Gerasimenko.

När  Rosetta  nådde  from  till  komet  67P/Churyumov–Gerasimenko  i augusti 2014 hade redan sju olika rymdfarkoster besökt nio olika ko- meter.  Rosetta  var  dock  den  första  missionen  som  cirklade  runt  en komet och följde den sedan i dess bana i totalt mer än två år. Detta motsvarade en signifikant del av hela kometens bana runt solen. Det- ta gjorde det möjligt att studera plasmats dynamiska utveckling un- der en period när kometen utvecklades från ett av de minsta hindren solvinden möter i solsystemet, när kometen är långt från solen, till enfullt utvecklad magnetosfär nära perihelion.

Avhandlingen behandlar främst den tidiga delen av denna utveckling, när nyligen joniserade molekyler från kometatmosfären börjar ge en signifikant störning i solvindens flöde. Under dessa förhållanden är en kinetisk beskrivning av växelverkan mellan solvinden och kome- tatmosfären  nödvändig.  Systemet  vi  studerar  kan  inte  reduceras  till ett hydrodynamiskt problem. Detta till skillnad från situationen när kometen är närmare solen, då växelverkan kan beskrivas med fluid- teori, för både Churyumov–Gerasimenko och de tidigare undersöktakometerna.

Rosetta var inte en mission främst ägnad åt plasma-studier. Detta med- förde begränsad rumslig täckning av de plasma-processer som äger rum, vilka äger rum över flera olika rumsskalor. Att förstå solvindens växleverkan  med  kometatmosfären  enbart  med  enpunktsmätningar låter sig därför inte göras. I detta arbete används därför en kombina- tion av experimentella data, analytiska beskrivningar och numeriska beräkningar. I kapitel 3 och 4 föreslår vi enkla modeller för att beskri- va jondynamiken och kometens plasmamiljö. Dessa testas sedan mot observationer och numeriska modeller. Tillsammans ger de en global beskrivning  av  solvindens  dynamik  när  den  flödar  genom  kometat- mosfären,  vilket  utforskas  i  både  2 och  3 dimensioner  (kapitel  5).  I kapitel 6 utforskar vi interaktionen som sker när kometen är närmaresolen, och hur den nu i högre grad kan beskrivas som en fluid.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Fusion, Plasma and Space Physics Aerospace Engineering
Research subject
Space Technology
Identifiers
urn:nbn:se:ltu:diva-68785 (URN)978-91-7790-156-3 (ISBN)978-91-7790-157-0 (ISBN)
Public defence
2018-10-12, Aulan, IRF, Rymdcampus, Kiruna, 09:00 (English)
Opponent
Supervisors
Available from: 2018-05-21 Created: 2018-05-18 Last updated: 2018-10-10Bibliographically approved

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