Near-Earth substorm features from multiple satellite observations
ABSTRACT This paper was published as Journal of Geophysical Research, 2008, 113, A07S26. Copyright 2008 American Geophysical Union. It is available from http://www.agu.org/pubs/crossref/2008/2007JA012738.shtml. Doi: 10.1029/2007JA012738 Metadata only entry 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 ≈ −5.5 R E 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.
- SourceAvailable from: Victor Alejandro Pinto[show abstract] [hide abstract]
ABSTRACT: During the last decade, a number of studies have shown that turbulent processes in the plasma sheet are very important for the analysis of the formation of quasi-stable plasma sheet configurations. The existence of this turbulence provides a self-consistent approach to study the dynamics of the Earth's magnetosphere, including the plasma sheet stability. The turbulence can also be very important for an understanding of the location of an isolated substorm expansion phase onset. In this study the level of turbulence has been evaluated by calculating the eddy diffusion coefficients using the Time History of Events and Macroscale Interactions during Substorms satellite data. It was found that the value of the eddy diffusion coefficients may vary by at least 3 orders of magnitude, generally ranging from 10(3) to 10(6) km(2)/s, increasing with the distance from the Earth. The area of low eddy diffusion coefficients, less than 10(4) km(2)/s, is situated at distances below 12 R(E) in the tail where we found the transition region between the dipole and the tail-like geomagnetic field configuration. This region is consistent with the location of isolated substorms, as indicated by the first auroral arc brightening situated at the equatorial edge of the auroral oval.Journal of Geophysical Research 01/2011; 116:A00I24. · 3.17 Impact Factor
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ABSTRACT: A model of alignment of the field-aligned current generator system in the disturbed magnetosphere is proposed. It has been found that Pedersen currents in the disturbed ionosphere of the auroral oval are meridional. They connect oppositely directed field-aligned currents (FACs) of two adjacent Iijima and Potemra (IP) regions. This supplements the dominant concept of currents in the literature, in which a substorm current wedge plays a major role. During the considered substorm, graphs have been obtained of changes in FAC intensities in each of the three Iijima and Potemra regions of the Northern Hemisphere. These new data suggest that during a disturbance, the Region 1 FAC and the sum of regions 2 and 0 FACs remain equal. The equality means that these three generators form a unified system. Inequalities of intensities between two FACs of different sign simultaneously observed in the dawn and dusk sectors have also been detected in each IP region. A conceptual model is proposed for the formation of this dawn-dusk asymmetry. In the model, in addition to FACs that close up in the ionosphere of the Northern Hemisphere, FACs connecting the two hemispheres are also presented. The conclusion is justified that the global magnetospheric dynamo operates as a voltage generator under relatively quiet (average) conditions, as during storms.Geomagnetism and Aeronomy 12/2011; 51(7). · 0.33 Impact Factor
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ABSTRACT: In this paper we present a short review of kinetic models of the thin current sheet and corresponding Cluster observations in the Earth magnetotail. We concentrate mainly on manifestations of non-fluid ion kinetic effects. We discuss the different approaches to model description of the proton component and show that current sheets observed by Cluster contain population of particles with transient trajectories, which, in fact, are main carriers of the transverse current in the Earth magnetotail. We describe the influence of the electron temperature anisotropy on the current sheet structure. We demonstrate that the decoupling of proton and electron motions in thin current sheets results in appearance of the earthward electrostatic field, which redistributes currents due to the cross-field drift. This effect can describe small or negative proton currents often observed by Cluster.Space Science Reviews 12/2012; · 5.52 Impact Factor