1. 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 1.UCL, Mullard Space Science Laboratory, Surrey, UK 2.Imperial College, London, UK 3.CNRS, IRAP, Toulouse, France UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS MULLARD SPACE SCIENCE LABORATORY

2. Magnetic Reconnection Observables First study of solar wind reconnection made by Gosling, 2005. Bifurcated current sheet Magnetic field rotations over current sheets Enhanced plasma jet / reconnection exhaust Reconnection Exhaust Adapted from Gosling, J.T. (2005) Inflow Magnetic Field Lines Current Sheet A1A2 B B

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

4. Phan,T.D (2006) 13 12 11 10 9 5 0 -10 -5 20 0 -20 -40 -340 -350 -360 32 m 00 s 34 m 00 s 02 h 30 m 00 s |B| (nT) B (nT) Ion Velocity (kms -1 ) Magnetic rotation at current sheets Previous study of reconnection event 02/02/2002 Data from Cluster 3 in GSE Total -- X -- Y -- Z --

5. Phan,T.D (2006) 13 12 11 10 9 5 0 -10 -5 20 0 -20 -40 -340 -350 -360 32 m 00 s 34 m 00 s 02 h 30 m 00 s |B| (nT) B (nT) Ion Velocity (kms -1 ) Magnetic rotation at current sheets Previous study of reconnection event 02/02/2002 Data from Cluster 3 in GSE Total -- X -- Y -- Z -- 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?

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. 7 53 h 30 m 6 6 40 20 0 52 h 30 m 53 h 00 m 54 h 00 m UT |B| (nT) Ion Velocity Enhancement (km s -1 ) Total -- X -- Y -- Z -- Reconnection Exhaust Magnetic Field and Ion Velocity Enhancement (GSE) Cluster 3 5 4 2 -2 18 16 14 12 B (nT) Density ( particles c m -3 )

8. 7 53 h 30 m 6 6 40 20 0 52 h 30 m 53 h 00 m 54 h 00 m UT |B| (nT) Ion Velocity Enhancement (km s -1 ) Total -- X -- Y -- Z -- Reconnection Exhaust Magnetic Field and Ion Velocity Enhancement (GSE) Cluster 3 5 4 2 -2 18 16 14 12 B (nT) Density ( particles c m -3 ) Inflow 1 speed = 48kms -1 Inflow 2 speed = 42kms -1 Average exhaust speed = 45kms -1

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

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

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

12. 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. Ongoing Work

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 10 6 km 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. B (nT) C1 C2 C3 C4 UT Total -- X -- Y -- Z -- Reconnection Event Interval Magnetic Field (GSE) Max R = 0.92 (x) Min R = 0.75 (y) Max R = 0.99 (z) Min R = 0.76 (y) Max R = 0.94 (z) Min R = 0.77 (y) Max R = 0.99 (x) Min R = 0.36 (y) Max R = 0.99 (z) Min R = 0.73 (y) Max R = 0.99 (y) Min R = 0.58 (x) 4 0 -4 4 0 4 0 4 0 52 m 00 s 52 m 30 s 53 m 00 s 53 m 30 s 54 m 00 s 54 m 30 s 55 m 00 s

18. B (nT) C1 C2 C3 C4 UT Total -- X -- Y -- Z -- Reconnection Event Interval Magnetic Field (GSE) 7 6 5 4 7 6 5 4 7 6 5 4 7 6 5 4 52 m 30 s 53 m 00 s 53 m 30 s 54 m 00 s 54 m 30 s