Presentation on theme: "On the nature of magnetosheath FTEs A.Roux, P.Robert, O.Le Contel, D.Fontaine, P.Canu (LPP) J.M. Bosqued, P. Louarn (IRAP) 1 Roux-Robert, IAGA 2013, Merida."— Presentation transcript:
On the nature of magnetosheath FTEs A.Roux, P.Robert, O.Le Contel, D.Fontaine, P.Canu (LPP) J.M. Bosqued, P. Louarn (IRAP) 1 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.
3 Roux-Robert, IAGA 2013, Merida Aug 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 E R )
4 Roux-Robert, IAGA 2013, Merida Aug 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 Context of the event C3
5 Roux-Robert, IAGA 2013, Merida Aug 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
6 Roux-Robert, IAGA 2013, Merida Aug 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
7 Roux-Robert, IAGA 2013, Merida Aug Discontinuities analysis A : 0 fp Free M. Sheath B : 2 fp M.Sphere C: 1 fp B.L. D : 1 fp C. M.Sheath 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 ?
8 Roux-Robert, IAGA 2013, Merida Aug Identification of discontinuities analysis GSE coordinates of the normal to discontinuity plane Accuracy of the measurement after simulation Angle (DB t, DV t ), 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: small : RD or shock N=Ct & Bn ≠ 0: RD Bn~0 & Vn~0 & DB t ≠ 0 : TD
9 Roux-Robert, IAGA 2013, Merida Aug 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 DIS frame & event chronology
Roux-Robert, IAGA 2013, Merida Aug 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
11 Roux-Robert, IAGA 2013, Merida Aug Conclusion