Merging 4 spacecraft data: Concepts used for analysing discontinuities

Dunlop, M. W.; Woodward, T. I.; Southwood, D. J.; Glaßmeier, Karl‐Heinz; Elphic, R. C.

doi:10.1016/s0273-1177(97)00566-8

Cited by 18 publications

(12 citation statements)

References 5 publications

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“…These are displayed in the spacecraft frame so that, for example, the bulk flow observed in the magnetosheath (V ) contrasts with the isotropic and stagnant nature of the SEC (II). The boundary mean normal speed is deduced from the application of the Planar Discontinuity Analysis technique (planar-DA) (Dunlop et al, 1997;Dunlop et al, 2003). This method uses the timings of the boundary crossings at each of the four spacecraft and compares it to the inter-spacecraft relative distance along the mean normal direction (over the four spacecraft), estimated through the MVA analysis.…”

Section: The 16/03/2002 Eventmentioning

confidence: 99%

The exterior cusp and its boundary with the magnetosheath: Cluster multi-event analysis

et al. 2004

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Abstract. We report on the observation of three high-altitude cusp crossings by the Cluster spacecraft under steady northward IMF conditions. The focus of this study is on the exterior cusp and its boundaries. At the poleward edge of the cusp, large downward jets are present; they are characterized by a dawn-dusk component of the convection velocity opposite to the IMF B y direction and a gradual evolution (velocity filter effect) corresponding to an injection site located at the high-latitude magnetopause tailward of the cusp, with subsequent sunward convection. As one moves from the poleward edge into the exterior cusp proper, the plasma gradually becomes stagnant as the result of the mirroring and scattering of the aforementioned plasma flows. The existence of such a stagnant region (Stagnant Exterior Cusp: SEC) is found in all events studied here even when the IMF B y is large and the clock angle is ∼90 • . The SEC-magnetosheath boundary appears as a spatial structure that has a normal component of the magnetic field pointing inward, in accordance with a probable connection between the region and the magnetosheath (with northward field). This boundary generally has a deHoffmann-Teller velocity that is slow and oriented sunward and downward, compatible with a discontinuity propagating from a location near the high-latitude magnetopause. Although the tangential stress balance is not always satisfied, the SEC-magnetosheath boundary is possibly a rotational discontinuity. Just outside this boundary, there exists a clear sub-Alfvénic plasma depletion layer (PDL). These results are all consistent with the existence of a nearly steady reconnection site at the high-latitude magnetopause tailward of the cusp. We suggest that the stability of the external discontinuity (and of the whole region) is maintained by the presence of the sub-Alfvénic PDL. However, examinationCorrespondence to: B. Lavraud (lavraud@lanl.gov) of the electron data shows the presence of heated electrons propagating parallel to the magnetic field (upward) just outside of the SEC-magnetosheath boundary. This appears inconsistent with their source being the northern lobe reconnection site. Finally, the definition of the magnetopause at high latitudes is revisited. To define the SEC-magnetosheath boundary as the magnetopause would lead to the misnaming of the "exterior cusp".

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Section: The 16/03/2002 Eventmentioning

confidence: 99%

The exterior cusp and its boundary with the magnetosheath: Cluster multi-event analysis

et al. 2004

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“…The intermediate-to-minimum eigenvalue ratio is around 2.5 for both crossings, but the normals are stable to variation of the computation interval. The application of the Planar Discontinuity Analysis (Planar DA) on the magnetic field time series (Dunlop et al, 1997) gives average normal speeds of $30 km/s for the two crossings. Moreover, the consistency of the normal derived from MVA with the delays in the Cluster four spacecraft time series is well established (see for example Dunlop et al, this issue).…”

Section: Overview Of Three Cluster High-altitude Cusp Passesmentioning

confidence: 99%

Cluster Observes the High-Altitude CUSP Region

et al. 2005

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This paper gives an overview of Cluster observations in the high-altitude cusp region of the magnetosphere. The low and mid-altitude cusps have been extensively studied previously with a number of low-altitude satellites, but only little is known about the distant part of the magnetospheric cusps. During the spring-time, the trajectory of the Cluster fleet is well placed for dayside, high-altitude magnetosphere investigations due to its highly eccentric polar orbit. Wide coverage of the region has resulted and, depending on the magnetic dipole tilt and the solar wind conditions, the spacecraft are susceptible to encounter: the plasma mantle, the high-altitude cusp, the dayside magnetosphere (i.e. dayside plasma sheet) and the distant exterior cusp diamagnetic cavity. The spacecraft either exit into the magnetosheath through the dayside magnetopause or through the exterior cusp-magnetosheath interface. This paper is based on Cluster observations made during three high-altitude passes. These were chosen because they occurred during different solar wind conditions and different interspacecraft separations. In addition, the dynamic nature of the cusp allowed all the aforementioned regions to be sampled with different order, duration and characteristics. The analysis deals with observations of: (1) both spatial and temporal structures at high-altitudes in the cusp and plasma mantle, (2) signatures of possible steady reconnection, flux transfer events (FTE) and plasma transfer events (PTE), (3) intermittent cold (<100 eV) plasma acceleration associated with both plasma penetration and boundary motions, (4) energetic ions (5-40 keV) in the exterior cusp diamagnetic cavity and (5) the global structure of the exterior cusp and its direct interface with the magnetosheath. The analysis is primarily focused on ion and magnetic field measurements. By use of these recent multi-spacecraft Cluster Surveys in Geophysics (2005) 26: 135-175 Ó Springer 2005observations we illustrate the current topics under debate pertaining to the solar wind-magnetosphere interaction, for which this region is known to be of major importance.

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“…In this context, collaboration with simultaneous ground-based observations is already playing a key role in relating magnetospheric responses with signatures observed by remote-sensing, ground-based instruments (Paschmann and Daly, 1998, chapters and references therein). The Cluster magnetometer team also published several aspects of four-point analysis techniques specifically related to magnetic field data since 1990 (for a comprehensive list of publications on this topic, see Balogh and Dunlop, 2000, but also Dunlop et al, 1996Dunlop et al, , 1997Woodward, 1998, 2000). First reviews of applications of these techniques using Cluster magnetic field data are presented in Dunlop et al (2001b), and Glassmeier et al (2001).…”

Section: Introduction: Scientific Objectives Of the Cluster Magnetic mentioning

confidence: 99%

The Cluster Magnetic Field Investigation: overview of in-flight performance and initial results

Balogh

Carr

Acuña³

et al. 2001

Ann. Geophys.

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1,127

979

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Abstract. The accurate measurement of the magnetic field along the orbits of the four Cluster spacecraft is a primary objective of the mission. The magnetic field is a key constituent of the plasma in and around the magnetosphere, and it plays an active role in all physical processes that define the structure and dynamics of magnetospheric phenomena on all scales. With the four-point measurements on Cluster, it has become possible to study the three-dimensional aspects of space plasma phenomena on scales commeasurable with the size of the spacecraft constellation, and to distinguish temporal and spatial dependences of small-scale processes. We present an overview of the instrumentation used to measure the magnetic field on the four Cluster spacecraft and an overview the performance of the operational modes used in flight. We also report on the results of the preliminary in-orbit calibration of the magnetometers; these results show that all components of the magnetic field are measured with an accuracy approaching 0.1 nT. Further data analysis is expected to bring an even more accurate determination of the calibration parameters. Several examples of the capabilities of the investigation are presented from the commissioning phase of the mission, and from the different regions visited by the spacecraft to date: the tail current sheet, the dusk side magnetopause and magnetosheath, the bow shock and the cusp. We also describe the data processing flow and the implementation of data distribution to other Cluster investigations and to the scientific community in general.

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Merging 4 spacecraft data: Concepts used for analysing discontinuities

Cited by 18 publications

References 5 publications

The exterior cusp and its boundary with the magnetosheath: Cluster multi-event analysis

The exterior cusp and its boundary with the magnetosheath: Cluster multi-event analysis

Cluster Observes the High-Altitude CUSP Region

The Cluster Magnetic Field Investigation: overview of in-flight performance and initial results

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