Inferring the Magnetotail reconnection model from its magnetic products Authors: S. Beyene1, C.J. Owen1, A.P. Walsh1, A.N. Fazakerley1, E. Lucek2, I. Dandouras3 1Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, RH5 6NT, UK 2Space and Atmospheric Physics, Imperial College London, SW7 2BZ, UK 3Centre d’Etude Spatiale des Rayonnements, Toulouse, France

The details of magnetic reconnection are not fully known. Motivation The details of magnetic reconnection are not fully known. Reconnection creates magnetic structures which have been observed. There are two competing models each predicting a magnetic structure (MXR and time dependant reconnection). By studying the magnetic structure, the correct model can be inferred (whether it be either, a hybrid or neither). We seek a crossing when spacecraft separation was similar to the size of these structures (~1.5RE, 2006 Tail Season, spacecraft 10,000km separation). Varied ‘impact parameters’ (unitless radial distance) one spacecraft outside, one near the centre and the other two at various distances inside the magnetic structure. 2 2

Multiple X-Line Reconnection Distance Dependant Multiple X lines present Flux ropes created between X-Lines Fastest X-Line Bipolar signature 3 3

Time Dependant Reconnection "from Kiehas et al., 2009" One X Line, two flux bulges MHD waves propagate from X-Line outflow tear drop shaped Uneven bipolar, plasma in second half 4 4

Data Search The Cluster data was searched to find a magnetic structure (in the tail) to analyse in the hopes of inferring the reconnection model. 5 5

Orbit Plot Relative to C3 In the Magnetotail Tetrahedral formation C3 far south 6 6

Spacecraft located in the magnetolobe Small, long lasting bipolar signature (compared to C1 and C4) Small increase in energy, density, pressure, temperature and velocity Event is consistent with a TCR (Travelling Compression Region) 7 7

Bipolar signature seen in Bz as well as a dip in Bx 0 and 180 degree pitch angle particles see a greater increase in DEF 8 8

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-ve Bx indicating a crossing of the neutral sheet Spacecraft crosses from plasma sheet to structure and back out into the plasma sheet No bipolar signature -ve Bx indicating a crossing of the neutral sheet Can be explained by the movement of the plasma sheet or by a magnetic structure 10 10

Possible Interpretations: Flux Rope 11 11

Possible Interpretations: Flux Bulge 12 12

Possible Interpretations: Wave 13 13

Summary Magnetic structures were searched for in the Cluster dataset, at a time when the spacecraft separation was close to the size of the magnetic structure. The event studied had the spacecraft at significantly different impact parameters. By analysing the structure, the reconnection model can be studied. Two reconnection models exist, both predicting different magnetic structures. By comparing the observed magnetic structure to the two theoretical magnetic structures, the reconnection model can be inferred Observed event more consistent with a plasma sheet wave sb2@mssl.ucl.ac.uk