Analysis of non-planar structures with multipoint measurements

Dunlop, M. W.; Woodward, T. I.; Motschmann, U.; Southwood, D. J.; Balogh, A.

doi:10.1016/0273-1177(95)00958-2

Cited by 6 publications

(5 citation statements)

References 1 publication

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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.

1,116

982

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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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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.

1,116

982

View full text Add to dashboard Cite

show abstract

“…Because of cloud expansion following the release, this boundary should be strongly curved between the two spacecraft and this appears to be con®rmed by boundary normals obtained from each data set. The sense of the curvature implied by the normals, which were obtained using a standard run, is described in Dunlop et al (1996) and is consistent with an expanding cloud where the eective tilt between the normal directions is $30±40°. Clearly, this event would be unsuitable for the discrete analysis in the manner discussed in Sect.…”

Section: Discussionmentioning

confidence: 52%

“…Additionally, the quality of any estimates of the macroscopic quantities depends upon the detailed microstructure in the sampled discontinuity, such as the presence of natural noise, wave or other properties, which can confuse simple model assumptions for the boundary unless either the structure is sampled fortuitously or judicious spectral ®ltering is possible. The latter will depend upon the degree to which the properties are in some sense con¯icting in their eect (see Dunlop et al, 1995;Dunlop et al, 1996, for more discussion of this point in the context of multi-spacecraft measurements).…”

Section: The Discontinuity Analysermentioning

confidence: 99%

Analysis of thick, non-planar boundaries using the discontinuity analyser

Dunlop

Woodward

1999

Ann Geophysicae

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The advent of missions comprised of phased arrays of spacecraft, with separation distances ranging down to at least mesoscales, provides the scienti®c community with an opportunity to accurately analyse the spatial and temporal dependencies of structures in space plasmas. Exploitation of the multi-point data sets, giving vastly more information than in previous missions, thereby allows unique study of their small-scale physics. It remains an outstanding problem, however, to understand in what way comparative information across spacecraft is best built into any analysis of the combined data. Dierent investigations appear to demand dierent methods of data co-ordination. Of the various multispacecraft data analysis techniques developed to aect this exploitation, the discontinuity analyser has been designed to investigate the macroscopic properties (topology and motion) of boundaries, revealed by multi-spacecraft magnetometer data, where the possibility of at least mesoscale structure is considered. It has been found that the analysis of planar structures is more straightforward than the analysis of non-planar boundaries, where the eects of topology and motion become interwoven in the data, and we argue here that it becomes necessary to customise the analysis for non-planar events to the type of structure at hand. One issue central to the discontinuity analyser, for instance, is the calculation of normal vectors to the structure. In the case of planar and`thin' non-planar structures, the method of normal determination is well-de®ned, although subject to uncertainties arising from unwanted signatures. In the case of`thick', non-planar structures, however, the method of determination becomes particularly sensitive to the type of physical sampling that is present. It is the purpose of this article to ®rstly review the discontinuity analyser technique and secondly, to discuss the analysis of the normals to thick non-planar structures detected in magnetometer data.

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“…Because of cloud expansion following the release, this boundary should be strongly curved between the two spacecraft and this appears to be con®rmed by boundary normals obtained from each data set. The sense of the curvature implied by the normals, which were obtained using a standard run, is described in Dunlop et al (1996) and is consistent with an expanding cloud where the e ective tilt between the normal directions is $30±40°. Clearly, this event would be unsuitable for the discrete analysis in the manner discussed in Sect.…”

Section: Discussionmentioning

confidence: 53%

“…Additionally, the quality of any estimates of the macroscopic quantities depends upon the detailed microstructure in the sampled discontinuity, such as the presence of natural noise, wave or other properties, which can confuse simple model assumptions for the boundary unless either the structure is sampled fortuitously or judicious spectral ®ltering is possible. The latter will depend upon the degree to which the properties are in some sense con¯icting in their e ect (see Dunlop et al, 1995;Dunlop et al, 1996, for more discussion of this point in the context of multi-spacecraft measurements).…”

Section: The Discontinuity Analysermentioning

confidence: 99%

Analysis of thick, non-planar boundaries using the discontinuity analyser

Dunlop

Woodward

1999

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. The advent of missions comprised of phased arrays of spacecraft, with separation distances ranging down to at least mesoscales, provides the scienti®c community with an opportunity to accurately analyse the spatial and temporal dependencies of structures in space plasmas. Exploitation of the multi-point data sets, giving vastly more information than in previous missions, thereby allows unique study of their small-scale physics. It remains an outstanding problem, however, to understand in what way comparative information across spacecraft is best built into any analysis of the combined data. Di erent investigations appear to demand di erent methods of data co-ordination. Of the various multispacecraft data analysis techniques developed to a ect this exploitation, the discontinuity analyser has been designed to investigate the macroscopic properties (topology and motion) of boundaries, revealed by multi-spacecraft magnetometer data, where the possibility of at least mesoscale structure is considered. It has been found that the analysis of planar structures is more straightforward than the analysis of non-planar boundaries, where the e ects of topology and motion become interwoven in the data, and we argue here that it becomes necessary to customise the analysis for non-planar events to the type of structure at hand. One issue central to the discontinuity analyser, for instance, is the calculation of normal vectors to the structure. In the case of planar and`thin' non-planar structures, the method of normal determination is wellde®ned, although subject to uncertainties arising from unwanted signatures. In the case of`thick', non-planar structures, however, the method of determination becomes particularly sensitive to the type of physical sampling that is present. It is the purpose of this article to ®rstly review the discontinuity analyser technique and secondly, to discuss the analysis of the normals to thick non-planar structures detected in magnetometer data.

show abstract

Analysis of non-planar structures with multipoint measurements

Cited by 6 publications

References 1 publication

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

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

Analysis of thick, non-planar boundaries using the discontinuity analyser

Analysis of thick, non-planar boundaries using the discontinuity analyser

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