Analysis of data from multi-satellite geospace missions

Motivation

Spacecraft are the primary means to explore the Earth's space environment. Multi-spacecraft missions such as Cluster and Themis have significantly advanced our understanding of geospace as a complex physical system. Special data analysis techniques are required to study large scale current systems, plasma waves and boundaries. The forthcoming three-satellite LEO mission Swarm will be operated as a geomagnetic observatory in space and address the spatiotemporal variability of current systems in the auroral zone.

Context and funding

• Principal investigator of the DFG funded project Multi-spacecraft analysis toolkit for Swarm in the context of the SPP 1488 Planetary magnetism. The project provides financial support for a Ph.D. student over three years (2011-2013), or, alternatively, for a postdoctoral researcher over 27 months. Collaborating institutions: GFZ Potsdam (Patricia Ritter, Hermann Lühr), FMI Helsinki (Olaf Amm).
• Organization of three international data analysis schools supported by COSPAR and other institutions: Sinaia, Romania (2007), Beijing, China (2004), and La Londe, France (2001).
• Co-Investigator of the Electron Drift Instrument (EDI) on the Cluster spacecraft.
• Member of several international teams funded by the International Space Science Institute (ISSI) in Bern.

The Cluster satellites as a multi-point array in geospace

In-situ observations of single-spacecraft missions in the magnetosphere and the solar wind do not allow for an unambiguous interpretation of the data in terms of spatial, temporal, or spatiotemporal variability. Multi-spacecraft missions such as ESA's four Cluster satellites (launched in the year 2000) allow for a much more complete understanding of the complex plasma processes in geospace. In the years 1996-1998, an international team supported by ISSI tailored array analysis techniques to the specifics of the Cluster mission, see the first volume SR-001 of the ISSI Scientific Report Series. In this context Vogt and Paschmann (1998) studied the accuracy of plasma moment derivative estimates. The wave surveyor technique, a fast method for wave vector identification, was introduced by Vogt et al. (2008a). The concept of reciprocal vectors was reviewed and generalized to missions of more than four spacecraft by Vogt et al. (2008b). Planar reciprocal vectors for three-spacecraft missions were introduced by Vogt et al. (2009).

The figure to the left is taken from Vogt et al. (2008a) and shows an application of the wave surveyor technique to Cluster magnetic field measurements (FGM instrument) in the foreshock region of the Earth's magnetosphere: dispersion relation (top) and propagation angles from the ambient magnetic field (bottom). The figure to the right shows pressure gradient estimates in the magnetotail based on the three-point gradient analysis of Cluster plasma measurements (CIS instrument), see Vogt et al. (2009) for details.

Multi-spacecraft analysis toolkit for Swarm

Data interpretation and global field modeling based on single-spacecraft magnetic measurements are generically limited by their spatiotemporal ambiguity. The forthcoming three-spacecraft ESA mission Swarm will be able to address this problem and thus provide a better separation of internal and external contributions to the Earth's magnetic field. To tap the full potential of Swarm's multi-point nature and also its combination of scientific instruments, we plan to tailor a data analysis toolkit to the specifics of the mission. In the context of the project Multi-spacecraft analysis toolkit for Swarm funded by DFG we will build on the efforts made in the context of ESA's multi-spacecraft mission Cluster and focus on the identification of auroral processes and current systems by in-situ measurements of the pair of SWARM satellites on the lower orbit of the constellation. Click on the image to the left to download the handout of a poster presented at the meeting of the DFG SPP 1488 Planetary magnetism in January 2010 in Potsdam.

Organization of data analysis workshops (lecture material online)

The following two workshops on analysis methods for multi-spacecraft data were part of the series of Capacity Building Workshops (CBWs) initiated by the Committee on Space Research (COSPAR).

• The third COSPAR CBW entitled Analysis of Data from Multisatellite Magnetospheric Missions took place in Beijing, China, from 4-13 May 2004. Visit the Beijing workshop web site for more information.
• The sixth COSPAR CBW entitled Solar-Terrestrial Interactions: Instrumentation and Techniques (STIINTE) took place in Sinaii, Romania, from 4-16 June 2007. Visit the Sinaia workshop web site for more information.

Recent team projects at ISSI

• Selected in 2010: Plasma Coupling in the Auroral Magnetosphere Ionosphere System.
• Selected in 2009: Directional Discontinuities in the Interplanetary Magnetic Field.

Refereed publications

Vogt, J., A. Albert, and O. Marghitu (2009), Analysis of three-spacecraft data using planar reciprocal vectors: methodological framework and spatial gradient estimation, Ann. Geophys. 27, 3249-3273.

Vogt, J., Y. Narita, and O.D. Constantinescu (2008a), The wave surveyor technique for fast plasma wave detection in multi-spacecraft data, Ann. Geophys. 26, 1699-1710.

Vogt, J., G. Paschmann, and G. Chanteur (2008b), Reciprocal Vectors, chapter~4 of the ISSI Scientific Report SR-008 entitled Multi-Spacecraft Analysis MethodsRevisited by G. Paschmann and P.W. Daly (eds.).

Glassmeier, K.-H., et al. -- 18 authors incl. J. Vogt (2008), Magnetospheric quasi-static response to the dynamic magnetosheath: A Themis case study, Geophys. Res. Lett. 35, L17S01, doi:10.1029/2008GL033469.

Glassmeier, K.-H., U. Motschmann, M. Dunlop, A. Balogh, M. H. Acuna, C. Carr, G. Musmann, K.-H. Fornacon, K. Schweda, J. Vogt, E. Georgescu, and S. Buchert (2001), Cluster as a wave telescope, Ann. Geophys. 19, 1439-1447.

Vogt, J., and G. Paschmann (1998), Accuracy of plasma moment derivatives, chapter 17 of the ISSI Scientific Report SR-001 entitled Analysis Methods for Multi-Spacecraft Data by G. Paschmann and P. Daly (eds.).

Supervised M.Sc. and B.Sc. theses

Albert, Adrian (2009), Three-point gradient estimation using planar reciprocal vectors M.Sc. thesis at Jacobs University Bremen.

Stroe, Andra (2009), Multipoint Analysis of Local Magnetohydrostatic Equilibria in the Earth's Magnetotail using Cluster II data B.Sc. thesis at Jacobs University Bremen.

Dabrowski, Peter (2004), Cluster II - Surveying Earth's Magnetosphere B.Sc. thesis at Jacobs University Bremen.