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Introduction

On the nature of magnetosheath FTEs A.Roux, P.Robert , O.Le Contel, D.Fontaine, P.Canu (LPP) J.M . Bosqued , P. Louarn (IRAP). Introduction. On January 26, 2001, CLUSTER S/C observe FTE at 11:32 and 12:10

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Introduction

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  1. On the nature of magnetosheath FTEs A.Roux, P.Robert, O.Le Contel, D.Fontaine, P.Canu (LPP)J.M. Bosqued, P. Louarn (IRAP) Roux-Robert, IAGA 2013, Merida Aug 25-31

  2. Introduction • On January 26, 2001, CLUSTER S/C observe FTE at 11:32 and 12:10 • Only the 11:32 event will be discussed here.Analyze the internal structure of a FTE is studied, namely: • Use magnetic field and particle data to identify discontinuities • Use energetic electrons as tracers of magnetic field lines inside the FTE • determine different regions depending on the number of magnetic footprint on Earth. Determine the nature of the discontinuities between these regions. Give evidence for magnetosheath electrons accelerated in // and anti//  directions. Roux-Robert, IAGA 2013, Merida Aug 25-31

  3. Position of the Flux Transfer Event (FTE) • Near the North-Est side of the magnetopause • T89 model give open or closed field lines for each S/C • Size of the tetrahedron ~500 km << FTE size (~1 ER) Roux-Robert, IAGA 2013, Merida Aug 25-31

  4. Context of the event • Minimum variance analysis • on more than 2 hours • Define Mag. Pause frame • Observe classical FTE • signatures : • inversion of normal component •  maximum on |Bo| • Strong ULF waves during • multiply MP crossings and FTE • Only studies of first FTE will • be shown here C3 Roux-Robert, IAGA 2013, Merida Aug 25-31

  5. Zoom on the FTE : field data • Aroud the FTE(zone A and D) B field is • Mag. Sheathtype, not Mag. Sphere • One can see 4 discontinuities on B • D1 is small, but visible on particle data • The event is composed of two different • parts: zone B and C defined by • disc. D1-D2 and D2-D3 • Strong decreasing of the potential, • so of the density, between D1 and DA •  Mag. Sphere • Strong ULF waves during all the FTE • duration Roux-Robert, IAGA 2013, Merida Aug 25-31

  6. Particle data • Density is decreasing during the first part (zone B) of the FTE • Typical of the Mag. Sphere • Velocity is increasing inside the structure • (zone B and C) • Around the structure, ions ~200 eV => typical of the Mag. Sheath, as suggested by wave data (A and D) • Inside the structure [DA-D3], ions ~1 keV • Associated with density ~ Mag Sheath • => MS ions has been accelerated and enter into the structure • Ions ~ 10 keV anti // B => escaping • Same for e- anti // B => escaping • Magnetosphere (zone B) identified by closed field lines (as many e- // as anti //) • zone C : open field lines (many e- // ) Regions delimited by discontinuities have been identified both by field and particle data Roux-Robert, IAGA 2013, Merida Aug 25-31

  7. Discontinuities analysis • Suppose plane discontinuity, • Ct. velocity • From time delays between 4 S/C • => computation of the normal • to the discontinuity plane • (method G. Chanteur) • D1,D2,D3 are separating • 2 different regions • DA is an only B discontinuity • & |B| anti correlated to Pot. (den) • D2 and D3 seems correspond • to a B rotation, with |B| CT. • => rotational discontinuity ? A : 0 fp Free M. Sheath B : 2 fp M.Sphere C: 1 fp B.L. D : 1 fp C. M.Sheath Roux-Robert, IAGA 2013, Merida Aug 25-31

  8. Identification of discontinuities analysis GSE coordinates of the normal to discontinuity plane Accuracy of the measurement after simulation Angle (DBt, DVt), see diagram Computed from Da Average on the 4 S/C of the normal component within the discontinuity Density jump Discontinuities identification : Tangential and rotational disc. delimit regions, DA is probably a slow shock • Reminder: • q small : RD or shock • N=Ct & Bn ≠ 0: RD • Bn~0 & Vn~0 & DBt≠ 0 : TD Roux-Robert, IAGA 2013, Merida Aug 25-31

  9. DIS frame & event chronology • Ion velocity anti// D • Penetrate into the • structure on open field • lines • Are accelerated • through D3 • Enter into the M. Sph. • through D2 • Slow down through DA • Recover their initial • velocity through D1 • when re-enter into • M. Sheath Roux-Robert, IAGA 2013, Merida Aug 25-31

  10. Summary / Conclusion Field and particle data allows us to Identify 4 space regions separated by 3 discontinuities Discontinuities identification is consistent with magnetic field direction inside each region Ions of Conn. M. Sheath are accelarated across D3 and penetrate into the M. Sphere Its are then slow down across the shock DA until the M. Sheath value Roux-Robert, IAGA 2013, Merida Aug 25-31

  11. Conclusion Conclusion Roux-Robert, IAGA 2013, Merida Aug 25-31

  12. Roux-Robert, IAGA 2013, Merida Aug 25-31

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