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, UK2Space and Atmospheric Physics, Imperial College London, SW7 2BZ, UK3Centre d’Etude Spatiale des Rayonnements, Toulouse, France

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.

Multiple X-Line Reconnection

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

Time Dependant Reconnection

•One X Line, two flux bulges•MHD waves propagate from X-Line•outflow tear drop shaped•Uneven bipolar, plasma in second half

"from Kiehas et al., 2009"

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.

Orbit Plot Relative to C3

•In the Magnetotail

•Tetrahedral

formation

•C3 far south

•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)

•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

•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

Possible Interpretations: Flux Rope

Possible Interpretations: Flux Bulge

Possible Interpretations: Wave

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