Evidence for transient, local ion foreshocks caused by dayside magnetopause reconnection

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http://hdl.handle.net/10138/170133

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Pfau-Kempf , Y , Hietala , H , Milan , S E , Juusola , L , Hoilijoki , S , Ganse , U , von Alfthan , S & Palmroth , M 2016 , ' Evidence for transient, local ion foreshocks caused by dayside magnetopause reconnection ' , Annales Geophysicae , vol. 34 , no. 11 , pp. 943-959 . https://doi.org/10.5194/angeo-34-943-2016

Title: Evidence for transient, local ion foreshocks caused by dayside magnetopause reconnection
Author: Pfau-Kempf, Yann; Hietala, Heli; Milan, Steve E.; Juusola, Liisa; Hoilijoki, Sanni; Ganse, Urs; von Alfthan, Sebastian; Palmroth, Minna
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2016-11-04
Language: eng
Number of pages: 17
Belongs to series: Annales Geophysicae
ISSN: 0992-7689
URI: http://hdl.handle.net/10138/170133
Abstract: We present a scenario resulting in time-dependent behaviour of the bow shock and transient, local ion reflection under unchanging solar wind conditions. Dayside magnetopause reconnection produces flux transfer events driving fast-mode wave fronts in the magnetosheath. These fronts push out the bow shock surface due to their increased downstream pressure. The resulting bow shock deformations lead to a configuration favourable to localized ion reflection and thus the formation of transient, travelling foreshock-like field-aligned ion beams. This is identified in two-dimensional global magnetospheric hybrid-Vlasov simulations of the Earth's magnetosphere performed using the Vlasiator model (http://vlasiator.fmi.fi). We also present observational data showing the occurrence of dayside reconnection and flux transfer events at the same time as Geotail observations of transient foreshock-like field-aligned ion beams. The spacecraft is located well upstream of the fore-shock edge and the bow shock, during a steady southward interplanetary magnetic field and in the absence of any solar wind or interplanetary magnetic field perturbations. This indicates the formation of such localized ion foreshocks.
Subject: Interplanetary physics (planetary bow shocks)
magnetospheric physics (magnetosheath; solar wind-magnetosphere interactions)
FLUX-TRANSFER EVENTS
EARTHS BOW SHOCK
INTERPLANETARY MAGNETIC-FIELD
HIGH-LATITUDE MAGNETOPAUSE
ELEMENTARY CURRENT SYSTEMS
HYBRID-VLASOV SIMULATION
WIND SPACECRAFT
THEMIS OBSERVATIONS
CLUSTER SPACECRAFT
RADAR OBSERVATIONS
115 Astronomy, Space science
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