1. 5. Walen Test analysis The Walen Test results for Cluster 3 are as expected for a reconnection event. The test over the leading edge shows a positive correlation and the trailing discontinuity shows a negative correlation. However the Walen Test over the discontinuities as seen by Cluster 1, does not show the same expected results. While the trailing discontinuity does show a negative correlation, there is no significant correlation at the leading edge. 6. Overall picture Thus the overall picture here is of a magnetic reconnection event with small scale differences which can be seen by the different Cluster spacecraft. The figure below shows the magnetic field (black) and ion velocity (red) vectors for the spacecraft traveling over the event. The black and blue line indicate the current sheets. 4. Observations The magnetic field for Cluster 1,3 and 4 show two distinctive sharp rotations, whereas Cluster 2 shows a gradual change in magnetic field over the same time frame. Small Scale Magnetic Reconnection in the Solar Wind 1.UCL, Mullar Space Science Laboratory, Dorking, Surrey, UK. 2.Imperial College, London, UK 3.CNRS, IRAP, Toulouse, France 1.Introduction It was discovered by Gosling et al., 2005 that magnetic reconnection was occurring in the solar wind environment. A study by Phan et al., 2009, found that the ACE and Wind spacecraft tend to witness the same events, leading to the conclusion that reconnection in the solar wind is large scale and non-patchy. In this study we will provide evidence to show that this is not always the case. We present a case study that shows significant variation over temporal scales of < 60s and /or spatial scales of < 10,000km. This study has found spatial and/or transient disturbances on scales shorter than 10,000km and 60 seconds, which means reconnection is not necessarily always large scale and non- patchy as has been previously surmised. 2. Magnetic Reconnection Magnetic reconnection is a fundamental plasma process that occurs in think current sheets, in which the frozen in field condition of MHD is violated in such a manner that pairs of magnetic field lines merge to produce topological changes in the field 3. Cluster Spacecraft 4 identical spacecraft travelling in an elliptical orbit around the Earth. In this case study the spacecraft are travelling in a tetrahedral shape of 10,000km side. The Fluxgate Magnetometer (FGM) and the Cluster Ion Spectrometry (CIS) instruments are used in this study. 7. Interpretation The differences between the magnetic field at Cluster 1,3, and 4 and Cluster 2, which encountered the event last, and the differences in the Walen test results from Cluster 1 and 3 suggests that either the event itself is a relatively small scale event, or that the reconnection is very short lived. 8. Conclusion In this study we have shown evidence that magnetic reconnection in the solar wind is variable on small temporal ( <60s) and /or spatial scales of (~10,000km). This result raises questions about our current understanding of magnetic reconnection in the solar wind. Courtesy of ESA