1. Studying Solar Wind Magnetic Reconnection Events using Cluster. A.C. Foster 1, C.J. Owen 1, A.N. Fazakerley 1, I. J. Rae 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) Magnetic rotation at current sheets Previous study of reconnection event 02/02/2002 Data from Cluster 3 in GSE Total -- X -- Y -- Z -- |B| (nT) B (nT) |velocity| (km/s) velocity (km/s) Universal Time

5. Study magnetic reconnection structures –Test the consistency of the temporal and spatial structure of magnetic reconnection from large scales to small scales –using the 4 Cluster spacecraft; multi-scale capacity Aim of Project

6. Case Study: Event 2/3/2006 |B| (nT) B (nT) |Velocity| (km/s) Velocity_x (km/s) Velocity_z (nT) Velocity_y (km/s) Density Total -- X -- Y -- Z --

7. Event 2/3/2006: Consistency Consistent with previous results The changes in V and B are correlated on one edge of the exhaust and anti-correlated on the other. The Walen test has been satisfied.

8. Event 2/3/2006: Characteristics Magnetic rotation over the event: 55 0 Angle between two main current sheets: 33 0 Low plasma β either side of the event, increase of plasma β during the event Alfven speed approximately 43km/s

9. Event 2/3/2006: Visualisation Maximum Variance Direction Minimum Variance Direction 10000-100000 10000 -10000 0 10000 0 -10000 0 10000 Courtesy of C. Forsyth, C.Owen, I.J. Rae CS1 -- CS2 – residual velocity  B Field  CS1 -- CS2 – residual velocity  B Field  Initial configuration Configuration with 2% alteration in background solar wind speed

10. Event 2/3/2006 |B| (nT) 8 0 8 0 8 0 0 8 37 m 30 s 40 m 00 s 37 m 30 s 40 m 00 s 37 m 30 s 40 m 00 s C4C3 C2C1 4 -2 4 44 B (nT) Universal Time Total -- X -- Y -- Z --

11. Also seen at ACE

12. Similar current sheets seen at ACE. Situated approximately 200R E away from the Cluster spacecraft Large overall structure (100s R E ) but there are small scale differences on the 10,000km scale. Discussion

13. Conclusions Small scale differences. In the solar wind the picture is of large scale, non patchy events Not all of the reconnection events fit the simple gosling bifurcated current sheet with the reconnection outflow between the two.

14. ● 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

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

16. Cluster Configuration

18. 2/3/2006