Evidence of Transverse Magnetospheric Field Line Oscillations as Observed from Cluster and Ground Magnetometers

Sinha, A. K. and Yeoman, T. K. and Wild, J. A. and Wright, D. M. and Cowley, S. W. H. and Balogh, A. (2005) Evidence of Transverse Magnetospheric Field Line Oscillations as Observed from Cluster and Ground Magnetometers. Annales Geophysicae, 23 (3). pp. 919-929. ISSN 0992-7689

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Abstract

The dynamic spectrum of ULF waves from magnetic field data obtained by the elliptically orbiting Cluster satellites (with an apogee of 119 000 km, perigee of 19 000 km and the orbital period of 57 h) have been prepared in the frequency range 0 to 120 mHz when the satellite was near its perigee. The existence of field line oscillations, with increasing frequency in the inbound sector and decreasing frequency in the outbound sector, is seen in the transverse components, indicating the presence of independently oscillating local magnetic flux tubes in the form of transverse standing Alfven waves. The results show that toroidal and poloidal modes are excited simultaneously. The analysis of simultaneous ground magnetometer data at the footprint of the satellite suggests that these modes are also excited due to coupling to magnetospheric waveguide modes. The clear signature of a resonant fundamental mode is seen in the ground data whereas Cluster detects a harmonic of this frequency. Lower frequency modes indicative of waveguide oscillations are seen in both the ground data and the compressional field at Cluster.

Item Type: Journal Article
Journal or Publication Title: Annales Geophysicae
Uncontrolled Keywords: /dk/atira/pure/subjectarea/asjc/1900/1912
Subjects:
Departments: Faculty of Science and Technology > School of Computing & Communications
Faculty of Science and Technology > Physics
ID Code: 9997
Deposited By: Dr Steve Marple
Deposited On: 24 Jun 2008 17:23
Refereed?: Yes
Published?: Published
Last Modified: 19 Aug 2019 00:39
URI: https://eprints.lancs.ac.uk/id/eprint/9997

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