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  • 1.
    Giang, Tony
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hamrin, Maria
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Yamauchi, Masatoshi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lundin, Rickard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nilsson, Hans
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ebihara, Yusuke
    Institute for Advanced Research, Nagoya University, Japan.
    Rème, Henri
    Centre d'Etude Spatiale des Rayonnements, Toulouse, France.
    Dandouras, Iannis
    Centre d'Etude Spatiale des Rayonnements, Toulouse, France.
    Vallat, C.
    VEGA contracted to Solar System Science Operations Division, ESA/ESAC, Madrid, Spain.
    Bavassano-Cattaneo, M. B.
    L'Istituto di Fisica dello Spazio Interplanetario, Roma, Italy.
    Klecker, B.
    Max Planck Institute for Extraterrestrial Physics, Garching, Germany.
    Korth, A.
    Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany.
    Kistler, L. M.
    University of New Hampshire, Durham, New Hampshire, USA.
    McCarthy, M.
    University of Washington, Seattle, USA.
    Outflowing protons and heavy ions as a source for the sub-keV ringcurrent2009Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, nr 2, s. 839-849Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Data from the Cluster CIS instrument have been used for studying proton and heavy ion (O+ and He+ ) char- acteristics of the sub-keV ring current. Thirteen events with dispersed heavy ions (O+ and He+ ) were identified out of two years (2001 and 2002) of Cluster data. Allevents took place during rather geomagnetically quiet periods. Three of those events have been investigated in detail: 21 August 2001, 26 November 2001 and 20 February 2002. These events were chosen from varying magnetic local times (MLT), and they showed different characteristics. In this article, we discuss the potential source for sub-keV ring current ions. We show that: (1) outflows of terrestrialsub-keV ions are supplied to the ring current also during quiet geomagnetic conditions; (2) the composition of the out-flow implies an origin that covers an altitude interval from the low-altitude ionosphere to the plasmasphere, and (3) terrestrial ions are moving upward along magnetic field lines, at times forming narrow collimated beams, but  frequently also as broad beams. Over time, the ion beams are expected to gradually become isotropised as a result of wave-particleinteraction, eventually taking the form of isotropic drifting sub-keV ion signatures. We argue that the sub-keV energy-time dispersed signatures originate from field-aligned terrestrial ion energising and outflow, which may occur at all local times and persist also during quiet times.

  • 2.
    Gunell, Herbert
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Belgium.
    Maggiolo, Romain
    Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Belgium.
    Nilsson, Hans
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Stenberg Wieser, Gabriella
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Slapak, Rikard
    EISCAT Scientific Association, Kiruna, Sweden.
    Lindkvist, Jesper
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hamrin, Maria
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    De Keyser, Johan
    Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Belgium.
    Why an intrinsic magnetic field does not protect a planet against atmospheric escape2018Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 614, artikel-id L3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The presence or absence of a magnetic field determines the nature of how a planet interacts with the solar wind and what paths are available for atmospheric escape. Magnetospheres form both around magnetised planets, such as Earth, and unmagnetised planets, like Mars and Venus, but it has been suggested that magnetised planets are better protected against atmospheric loss. However, the observed mass escape rates from these three planets are similar (in the approximate (0.5–2) kg s−1 range), putting this latter hypothesis into question. Modelling the effects of a planetary magnetic field on the major atmospheric escape processes, we show that the escape rate can be higher for magnetised planets over a wide range of magnetisations due to escape of ions through the polar caps and cusps. Therefore, contrary to what has previously been believed, magnetisation is not a sufficient condition for protecting a planet from atmospheric loss. Estimates of the atmospheric escape rates from exoplanets must therefore address all escape processes and their dependence on the planet’s magnetisation.

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