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    ABSTRACT: In addition to the high temperatures, SOHO/UVCS observations have shown that heavy ions in the polar corona are heated more than protons, and that heavy ion heating is more than mass proportional; further, the perpendicular temperatures are much larger than parallel temperatures. Here, we propose that the more than mass proportional heating of heavy ions in coronal holes is due to the ion reflection at supercritical quasi-perpendicular shocks and to the ion acceleration by the motional electric field in the shock frame. We also discuss the formation of collisionless shock in the polar corona.
    Twelfth International Solar Wind Conference. 03/2010;
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    ABSTRACT: The Earth’s bow shock is the most studied example of a collisionless shock in the solar system. It is also widely used to model or predict the behaviour at other astrophysical shock systems. Spacecraft observations, theoretical modelling and numerical simulations have led to a detailed understanding of the bow shock structure, the spatial organization of the components making up the shock interaction system, as well as fundamental shock processes such as particle heating and acceleration. In this paper we review the observations of accelerated ions at and upstream of the terrestrial bow shock and discuss the models and theories used to explain them. We describe the global morphology of the quasi-perpendicular and quasi-parallel shock regions and the foreshock. The acceleration processes for field-aligned beams and diffuse ion distribution types are discussed with connection to foreshock morphology and shock structure. The different possible mechanisms for extracting solar wind ions into the acceleration processes are also described. Despite several decades of study, there still remain some unsolved problems concerning ion acceleration at the bow shock, and we summarize these challenges.
    Space Science Reviews 11/2012; 173(1-4). · 5.52 Impact Factor
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    ABSTRACT: Among several mechanisms issued from simulation and theoretical studies proposed to account for the nonstationarity of quasi-perpendicular supercritical shocks, one process-the so-called self-reformation-driven by the accumulation of reflected ions in the foot has been intensively analyzed with simulations. Present results based on experimental CLUSTER mission clearly evidence signatures of this self-reformation process for the terrestrial bow shock. The study based on magnetic field measurements includes two parts: (i) a detailed analysis of one typical shock crossing for almost perpendicular shock directions where the risk of pollution by other nonstationarity mechanisms is minimal. A special attention is drawn on appropriate treatment of data to avoid any wrong interpretation. One key result is that the ramp width can reach a very narrow value covering a few electron inertial lengths only; (ii) a statistical analysis allows relating the signatures of this nonstationarity with different plasma conditions and shock regimes. Present results are discussed in comparison with previous simulation works.
    Twelfth International Solar Wind Conference. 03/2010;

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