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Studying Solar Wind Magnetic Reconnection Events using the Cluster 4-point Measurement Capability

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS MULLARD SPACE SCIENCE LABORATORY. Studying Solar Wind Magnetic Reconnection Events using the Cluster 4-point Measurement Capability. A.C. Foster 1 , C.J. Owen 1 , A.N. Fazakerley 1 , C. Forsyth 1 E. Lucek 2 , H. Rème 3

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Studying Solar Wind Magnetic Reconnection Events using the Cluster 4-point Measurement Capability

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  1. UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS MULLARD SPACE SCIENCE LABORATORY Studying Solar Wind Magnetic Reconnection Events using the Cluster 4-point Measurement Capability A.C. Foster1, C.J. Owen1, A.N. Fazakerley1, C. Forsyth1 E. Lucek2, H. Rème3 UCL, Mullard Space Science Laboratory, Surrey, UK Imperial College, London, UK CNRS, IRAP, Toulouse, France

  2. First study of solar wind reconnection made by Gosling, 2005. Bifurcated current sheet Magnetic field rotations over current sheets Enhanced plasma jet / reconnection exhaust Magnetic Reconnection Observables Reconnection Exhaust B A1 A2 Inflow Inflow Magnetic Field Lines Current Sheet Inflow Inflow Adapted from Gosling, J.T. (2005) B Reconnection Exhaust

  3. Advantages in studying Reconnection in the Solar Wind • Unconstrained boundary conditions • Multiple spacecraft observations • Time scales ≤ few hours • Length scales ~100s RE • Different plasma conditions than frequently studied (e.g. Magnetopause / magnetotail) Jet BM ACE To Sun Exhaust Earth Cluster Wind Solar Wind Direction Phan,T.D (2006) Jet

  4. Previous study of reconnection event 02/02/2002 Total -- X -- Y --Z -- |B| (nT) 13 12 11 10 Magnetic rotation at current sheets 9 5 B (nT) 0 -5 -10 Ion Velocity (kms-1) 0 -20 -40 20 -340 -350 -360 Phan,T.D (2006) 02h 30m00s 32m00s 34m00s Data from Cluster 3 in GSE

  5. Previous study of reconnection event 02/02/2002 Total -- X -- Y --Z -- |B| (nT) 13 12 11 10 Magnetic rotation at current sheets 9 Using Cluster’s 4 point-measurement capability it was not possible to reproduce these results. Small scale features (e.g. Ripples in the current sheets) in these reconnection events? 5 B (nT) 0 -5 -10 Ion Velocity (kms-1) 0 -20 -40 20 -340 -350 -360 Phan,T.D (2006) 02h 30m00s 32m00s 34m00s Data from Cluster 3 in GSE

  6. My study will initially look at the magnetic reconnection structures on a relatively small scale using the 4 Cluster spacecraft. This is in order to test more detailed reconnection models: is it possible to predict the outflow conditions given the inflow conditions? The extended study will look at the events on a larger scale using ACE and Wind. Aim of Project

  7. Magnetic Field and Ion Velocity Enhancement (GSE) Total -- X -- Y --Z -- Cluster 3 7 |B| (nT) 6 5 4 6 B (nT) 2 -2 Ion Velocity Enhancement (km s-1) 40 Reconnection Exhaust 20 0 18 Density (particles cm-3) 16 14 UT 12 52h30m 53h30m 54h00m 53h00m

  8. Magnetic Field and Ion Velocity Enhancement (GSE) Total -- X -- Y --Z -- Cluster 3 • Inflow 1 speed = 48kms-1 • Inflow 2 speed = 42kms-1 • Average exhaust speed = 45kms-1 7 |B| (nT) 6 5 4 6 B (nT) 2 -2 Ion Velocity Enhancement (km s-1) 40 Reconnection Exhaust 20 0 18 Density (particles cm-3) 16 14 UT 12 52h30m 53h30m 54h00m 53h00m

  9. Current Sheet Orientation Determination Minimum Variance Technique • Results were consistent between spacecraft. • In all cases: • Normal direction vector taken as minimum variance direction To the Sun Earth Solar Wind Direction X-Line Sheet 1 Sheet 2 Sheet 1 Sheet 2

  10. Current Sheet Co-ordinate System Determination X-line Direction • Cross product of the normal direction vector of each current sheet • Point on plane – position that Cluster 3 encounterssheet. • Right handed system for each current sheet To the Sun Earth Solar Wind Direction Assumption made: Current sheets can be considered as flat planes X-Line Sheet 1 Sheet 2 Sheet 1 Sheet 2

  11. Exhaust Velocity Determination • Average velocity lies between current sheets • Perpendicular to X-direction Reconnection Exhaust Sheet 1 Sheet 2 X-Point Cluster 3 trajectory through exhaust

  12. Ongoing Work • Comparing the data to more detailed reconnection models • Looking at the small scale features in these large scale structures • Comparing the Cluster data with data from ACE and Wind which also saw the event.

  13. Baumjohann, W. (1997): Wolfgang Baumjohann and Rudolf A. Treumann. Basics of Space Plasma Physics. Imperial College Press, 1997. Priest, E. R. (1984): Priest, E. R. (1984), Solar Magneto-Hydrodynamics, Geophys. Astrophys.Monogr. Ser., Springer, New York. Gosling, J.T (2005): J.T. Gosling, R.M. Skoug, D.J. McComas, C.W. Smith, J. Geophys. Res. 110, A01107, 2005 Phan, T. D. (2006): T. D. Phan, J. T. Gosling, M. S. Davis, R. M. Skoug, M. Øieroset, R. P. Lin, R. P. Lepping, D. J.McComas, C. W. Smith, H. Reme, and A. Balogh. A magnetic reconnection X-line extending more than 390 Earth radii in the solar wind. Nature, 439:175–178, January 2006. Gosling (2007): J. T. Gosling, S. Eriksson,L. M. Blush,T. D. Phan,J. G. Luhmann,D. J. McComas,R. M. Skoug,M. H. Acuna,C. T. Russell, and K. D. Simunac. Five spacecraft observations of oppositely directed exhaust jets from a magnetic reconnection X-line extending > 4.26 106km in the solar wind at 1 AU References UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS MULLARD SPACE SCIENCE LABORATORY

  14. UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS MULLARD SPACE SCIENCE LABORATORY

  15. Minimum Variance Analysis

  16. Cluster Configuration

  17. Magnetic Field (GSE) Total -- X -- Y --Z -- Reconnection Event Interval Max R = 0.99 (x) Min R = 0.36 (y) C1 Max R = 0.92 (x) Min R = 0.75 (y) Max R = 0.99 (z) Min R = 0.73 (y) C2 B (nT) Max R = 0.99 (z) Min R = 0.76 (y) 4 4 4 4 C3 0 0 0 0 -4 -4 -4 -4 Max R = 0.99 (y) Min R = 0.58 (x) C4 Max R = 0.94 (z) Min R = 0.77 (y) 52m30s 55m00s 53m00s 53m30s 54m00s 54m30s 52m00s UT

  18. Magnetic Field (GSE) Total -- X -- Y --Z -- Reconnection Event Interval 7 7 7 7 6 6 6 6 C1 5 5 5 5 4 4 4 4 C2 B (nT) C3 C4 54m00s 52m30s 53m00s 53m30s 54m30s UT

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