M. Volwerk

Near-Earth substorm features from multiple satellite observations

We investigate a substorm on 3 October 2004 during which 11 satellites were located in near-Earth magnetotail (X-GSM > -10 R-E). Double Star 1 (TC-1), Cluster, and LANL-97 satellites were closely aligned in the dawn-dusk direction (<1 R-E apart) for this conjunction. After substorm expansion onset, TC-1 observed plasma sheet thinning at X approximate to -5.5 RE and later detected signature of plasma flow shear that may be associated with an auroral arc. Analysis of the dawn-dusk magnetic perturbations from GOES-10 and Polar suggests that these could be caused by a substorm current system consisting of not only the azimuthal closure of field-aligned currents (the substorm current wedge) but also the meridional closure of field-aligned currents. The temporal sequence of substorm activity (particle injection, current disruption, and dipolarization) revealed by these satellites indicates that the substorm expansion activity was initiated close to the Earth and spread later to further downstream distances. Furthermore, TC-1 and Cluster data show that there is no close relationship between some dipolarizations and Earthward plasma flows in the near-Earth region. The overall development of substorm activity is in agreement with the near-Earth initiation model for substorms. A temporal evolution of the magnetic field reconfiguration and plasma boundary motion during this substorm is constructed from these observations.

Study of reconnection-associated multiscale fluctuations with cluster and double star

The objective of the paper is to asses the specific spectral scaling properties of magnetic reconnection associated fluctuations/turbulence at the Earthward and tailward outflow regions observed simultaneously by the Cluster and Double Star (TC-2) spacecraft on September 26, 2005. Systematic comparisons of spectral characteristics, including variance anisotropy and scale-dependent spectral anisotropy features in wave vector space were possible due to the well-documented reconnection events, occurring between the positions of Cluster (X = -14--16

Magnetotail dipolarization and associated current systems observed by Cluster and Double Star

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Europa's Alfvén wing: shrinkage and displacement influenced by an induced magnetic field

) and TC-2 (X = -6.6

Study of waves in the magnetotail region with cluster and DSP

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Plasma sheet oscillations and their relation to substorm development: cluster and double star TC1 case study

). Another factor of key importance is that the magnetometers on the spacecraft are similar. The comparisons provide further evidence for asymmetry of physical processes in Earthward/tailward reconnection outflow regions. Variance anisotropy and spectral anisotropy angles estimated from the multi-scale magnetic fluctuations in the tailward outflow region show features which are characteristic for magnetohydrodynamic cascading turbulence in the presence of a local mean magnetic field. The multi-scale magnetic fluctuations in the Earthward outflow region are exhibiting more power, lack of variance and scale dependent anisotropies, but also having larger anisotropy angles. In this region the magnetic field is more dipolar, the main processes driving turbulence are flow breaking/mixing, perhaps combined with turbulence ageing and non-cascade related multi-scale energy sources.