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  • 1.
    Behar, Etienne
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Lindkvist, Jesper
    Swedish Institute of Space Physics, Kiruna.
    Nilsson, Hans
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Holmström, Mats
    Swedish Institute of Space Physics, Kiruna.
    Stenberg-Wieser, G.
    Swedish Institute of Space Physics, Kiruna.
    Ramstad, Robin
    Swedish Institute of Space Physics, Kiruna.
    Götz, C.
    Technicsche Universitåt Braunschweig, Institute for Geophysics and Extraterrestrial Physics, Braunschweig.
    Mass-loading of the solar wind at 67P/Churyumov-Gerasimenko: Observations and modelling2016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 596, A42Article in journal (Refereed)
    Abstract [en]

    Context. The first long-term in-situ observation of the plasma environment in the vicinity of a comet, as provided by the European Rosetta spacecraft. Aims. Here we offer characterisation of the solar wind flow near 67P/Churyumov-Gerasimenko (67P) and its long term evolution during low nucleus activity. We also aim to quantify and interpret the deflection and deceleration of the flow expected from ionization of neutral cometary particles within the undisturbed solar wind. Methods. We have analysed in situ ion and magnetic field data and combined this with hybrid modeling of the interaction between the solar wind and the comet atmosphere. Results. The solar wind deflection is increasing with decreasing heliocentric distances, and exhibits very little deceleration. This is seen both in observations and in modeled solar wind protons. According to our model, energy and momentum are transferred from the solar wind to the coma in a single region, centered on the nucleus, with a size in the order of 1000 km. This interaction affects, over larger scales, the downstream modeled solar wind flow. The energy gained by the cometary ions is a small fraction of the energy available in the solar wind. Conclusions. The deflection of the solar wind is the strongest and clearest signature of the mass-loading for a small, low-activity comet, whereas there is little deceleration of the solar wind

  • 2.
    Behar, Etienne
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Nilsson, Hans
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics.
    Nemeth, Zoltan
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Brolles, T.W.
    Space Science and Engineering Division, Southwest Research Institute, San Antonio.
    Richter, Ingo
    Technische Universität–Braunschweig, Institute for Geophysics and Extraterrestrial Physics.
    Mass loading at 67P/Churyumov-Gerasimenko: A case study2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 4, 1411-1418 p.Article in journal (Refereed)
    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.

  • 3.
    Brolies, Thomas W.
    et al.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio, Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Clark, Grace A.
    Heliophysics Division, Goddard Space Flight Center.
    Koenders, Christoph
    Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig.
    Behar, Etienne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Goldstein, Raymond M.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Fuselier, Stephen Anthony
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mandt, Kathleen E.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio, Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Samara, M.
    Heliophysics Division, Goddard Space Flight Center.
    Rosetta observations of solar wind interaction with the comet 67P/Churyumov-Gerasimenko2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, A21Article in journal (Refereed)
    Abstract [en]

    Context. The Rosetta spacecraft arrived at the comet 67P/Churyumov-Gerasimenko on August 6, 2014, which has made it possible to perform the first study of the solar wind interacting with the coma of a weakly outgassing comet. Aims. It is shown that the solar wind experiences large deflections (>45°) in the weak coma. The average ion velocity slows from the mass loading of newborn cometary ions, which also slows the interplanetary magnetic field (IMF) relative to the solar wind ions and subsequently creates a Lorentz force in the frame of the solar wind. The Lorentz force in the solar wind frame accelerates ions in the opposite direction of cometary pickup ion flow, and is necessary to conserve momentum. Methods. Data from the Ion and Electron Sensor are studied over several intervals of interest when significant solar wind deflection was observed. The deflections for protons and for He++ were compared with the flow of cometary pickup ions using the instrument's frame of reference. We then fit the data with a three-dimensional Maxwellian, and rotated the flow vectors into the Comet Sun Equatorial coordinate system, and compared the flow to the spacecraft's position and to the local IMF conditions. Results. Our observations show that the solar wind may be deflected in excess of 45° from the anti-sunward direction. Furthermore, the deflections change direction on a variable timescale. Solar wind protons are consistently more deflected than the He++. The deflections are not ordered by the spacecraft's position relative to the comet, but large changes in deflection are related to changes in the orthogonal IMF components

  • 4.
    Ekman, Jonas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Törlind, Peter
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nilsson, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Öhrwall Rönnbäck, Anna
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Zorzano Mier, Maria-Paz
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Parida, Vinit
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Behar, Etienne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Wolf, Veronika
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Dordlofva, Christo
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Mendaza de Cal, Maria Teresa
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Jamali, Maryam
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Roos, Tobias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ottemark, Rikard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nieto, Chris
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Soria Salinas, Álvaro Tomás
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Vázquez Martín, Sandra
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nyberg, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Neikter, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindwall, Angelica
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Fakhardji, Wissam
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Projekt: Rymdforskarskolan2015Other (Other (popular science, discussion, etc.))
    Abstract [en]

    The Graduate School of Space Technology

  • 5.
    Nilsson, Hans
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics.
    Behar, Etienne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Wedlund, Cyril Simon
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Gunell, Herbert
    Belgian Institute for Space Aeronomy, Brussels.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics.
    Lundin, Rickard
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Swedish Institute of Space Physics.
    Wieser, Martin
    Swedish Institute of Space Physics.
    Carr, Chris
    Imperial College London.
    Cupido, Emanuele
    Imperial College London.
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Fedorov, Andrei
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Savaud, Jean-André
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Koskinen, Hannu
    Department of Physics, University of Helsinki.
    Kallio, Esa
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Lebreton, Jean-Pierre
    Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E).
    Eriksson, Anders
    Swedish Institute of Space Physics, Ångström Laboratory.
    Edberg, Niklas
    Swedish Institute of Space Physics, Ångström Laboratory.
    Goldstein, Raymond
    Belgian Institute for Space Aeronomy, Brussels.
    Henri, Pierre
    Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E).
    Coenders, Christoph
    Technische Universität–Braunschweig, Institute for Geophysics and Extraterrestrial Physics.
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Nemeth, Zoltan
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Richter, Ingo
    Technische Universität–Braunschweig, Institute for Geophysics and Extraterrestrial Physics.
    Rubin, Martin
    Physikalisches Institut, University of Bern.
    Birth of a comet magnetosphere: A spring of water ions2015In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 347, no 6220, aaa0571Article in journal (Refereed)
    Abstract [en]

    The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (~3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (

  • 6.
    Nilsson, Hans
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics.
    Behar, Etienne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Wedlund, Cyril Simon
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Kallio, Esa
    Finnish Meteorological Institute, Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Gunell, Herbert
    Swedish Institute of Space Physics / Institutet för rymdfysik , Belgian Institute for Space Aeronomy, Brussels.
    Edberg, N.J.T.
    Swedish Institute of Space Physics, Uppsala.
    Eriksson, Anders
    Swedish Institute of Space Physics, Ångström Laboratory.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics.
    Koenders, Christoph
    Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig.
    Wieser, Martin
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Lundin, Rickard
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Mandt, Kathleen E.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Goldstein, Raymond M.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Carr, Chris
    Imperial College London.
    Cupido, Emanuele
    Imperial College London.
    Fox, P.T.
    Imperial College London.
    Szego, Karoly
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Nemeth, Zoltan
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Fedorov, Andrei
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Sauvaud, J.A.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Koskinen, Hannu
    Department of Physics, University of Helsinki.
    Geiger, B.
    Rosetta Science Ground Segment, Science and Robotic Exploration (SRE-OOR).
    Evolution of the ion environment of comet 67P/Churyumov-Gerasimenko2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, A20Article in journal (Refereed)
    Abstract [en]

    Context. The Rosetta spacecraft is escorting comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 AU, where the comet activity was low, until perihelion at 1.24 AU. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation. Aims. Using the Rosetta Plasma Consortium Ion Composition Analyzer (RPC-ICA), we study the gradual evolution of the comet ion environment, from the first detectable traces of water ions to the stage where cometary water ions accelerated to about 1 keV energy are abundant. We compare ion fluxes of solar wind and cometary origin. Methods. RPC-ICA is an ion mass spectrometer measuring ions of solar wind and cometary origins in the 10 eV-40 keV energy range. Results. We show how the flux of accelerated water ions with energies above 120 eV increases between 3.6 and 2.0 AU. The 24 h average increases by 4 orders of magnitude, mainly because high-flux periods become more common. The water ion energy spectra also become broader with time. This may indicate a larger and more uniform source region. At 2.0 AU the accelerated water ion flux is frequently of the same order as the solar wind proton flux. Water ions of 120 eV-few keV energy may thus constitute a significant part of the ions sputtering the nucleus surface. The ion density and mass in the comet vicinity is dominated by ions of cometary origin. The solar wind is deflected and the energy spectra broadened compared to an undisturbed solar wind.

  • 7.
    Wedlund, Cyril Simon
    et al.
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Kallio, Esa
    Finnish Meteorological Institute, Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Alho, Markku
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Nilsson, Hans
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics.
    Gunell, Herbert
    Swedish Institute of Space Physics / Institutet för rymdfysik , Belgian Institute for Space Aeronomy, Brussels.
    Behar, Etienne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Pusa, J.
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Gronoff, Guillaume
    Science Directorate, Chemistry and Dynamics Branch, NASA Langley Research Center, Hampton, Virginia.
    The atmosphere of comet 67P/Churyumov-Gerasimenko diagnosed by charge-exchanged solar wind alpha particles2016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 587, A154Article in journal (Refereed)
    Abstract [en]

    Context. 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.

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