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Cluster multi-point observations of the magnetotail plasma sheet.

Henderson, P.D.; (2008) Cluster multi-point observations of the magnetotail plasma sheet. Doctoral thesis , University of London. Green open access

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Abstract

This thesis presents observations of the terrestrial magnetotail plasma sheet made by the European Space Agency Cluster mission. The Cluster mission is composed of four identical spacecraft, the first such multi-spacecraft mission, and enables, for the first time, the disambiguation of time versus space phenomena. Using the data from 2003, when the spacecraft were at their smallest average separation to date, many small-scale processes, both microphysical and macrophysical, are investigated. In the first study presented, two small flux ropes, a possible signature of multiple X-line reconnection, are investigated. By the development and utilisation of various multi-spacecraft methods, the currents and magnetic forces internal and external to the flux ropes, as well as the internal structure of the flux ropes, are investigated. In addition, a theory of their early evolution is suggested. In the second study presented, various terms of the generalised Ohm's law for a plasma are determined, including, for the first time, the divergence of the full electron pressure tensor, during the passage past the spacecraft of an active reconnection X-line. It is found that the electric field contribution from the divergence of the electron pressure tensor is anti-correlated with the contribution from the Hall term in the direction normal to the neutral sheet. In addition, further signatures of reconnection are quantified, such as parallel electric field generation and Hall quadrupolar magnetic field and current systems. In the final study presented, the anti-correlation between the divergence of the electron pressure tensor and Hall terms is investigated further. It is found that the anti-correlation is general, appearing in the direction normal to the neutral sheet because of a cross tail current. In a simple magnetohydrostatic treatment, a force balance argument leads to the conclusion that the gradient of the anti-correlation is a function of the ratio of the electron to ion temperatures, as well as providing information regarding the spatial scales of the pressure tensors.

Type: Thesis (Doctoral)
Title: Cluster multi-point observations of the magnetotail plasma sheet.
Identifier: PQ ETD:591601
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest. Third party copyright material has been removed from the ethesis
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/1444299
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