Abstract
Abstract. We present observations of three magnetic flux ropes in the tail of the Earth's magnetosphere on 7 August 2004 by the Cluster and Double Star TC-1 spacecraft. The first two flux rope signatures were observed, near-simultaneously, by Cluster and TC-1, which were located at (–16.3, –8.7, 0.10) RE GSM and (–10.3, –7.11, 0.81) RE GSM, respectively, a separation of 6.3 RE. A third signature was observed some four minutes later by two of the four Cluster spacecraft, while the other two spacecraft observed a feature resembling a Travelling Compression Region (TCR). These observations are interpreted as three individual flux ropes existing in the magnetotail, the first two, at least, simultaneously. The formation mechanism of the flux ropes and the consequences of their presence for the structure of the magnetotail on this day are discussed in the context of multiple X-point reconnection.
Highlights
A widely invoked substorm model, the Near-Earth Neutral Line (NENL) Model (e.g. Baker et al, 1996), involves reconnection at a neutral point in the near-Earth tail. This model does not emphasize the possibility of reconnection at more than one site in the tail, or so-called multiple X-point reconnection (MXR)
If there is a cross-tail component of the magnetic field present in the magnetotail, the reconnected flux that lies between the X-lines is expected to form helical structures of magnetic flux, or magnetic flux ropes (Hughes and Sibeck, 1987)
While bipolar signatures in the magnetic field can be caused by numerous phenomena, the observation of a well-formed core field in these events means that these signatures can be interpreted in terms of a simple flux rope model as an Earthward moving flux rope passing over the spacecraft
Summary
There is a theoretical basis for MXR (Zwingmann, 1983), and its relation to flux ropes (Ogino et al, 1990), observational evidence is often based on measurements taken either by a single spacecraft or at a single location in the tail (e.g. Eastwood et al, 2005). There is a theoretical basis for MXR (Zwingmann, 1983), and its relation to flux ropes (Ogino et al, 1990), observational evidence is often based on measurements taken either by a single spacecraft or at a single location in the tail Observations of structures related to MXR, for example flux ropes, existing simultaneously at different locations in the tail would provide valuable experimental evidence for the theory. To the best of our knowledge, these are the first such observations
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