Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study
Three ULF wave events, all occurring in the dayside magnetopshere during magnetically quiet times, are studied using the Cluster satellites. The multi-point measurements obtained from Cluster are used to determine the azimuthal wave number for the events by means of the phase shift and the azimu...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2005-10-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/23/2679/2005/angeo-23-2679-2005.pdf |
| _version_ | 1817970238630658048 |
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| author | P. T. I. Eriksson L. G. Blomberg A. D. M. Walker K.-H. Glassmeier |
| author_facet | P. T. I. Eriksson L. G. Blomberg A. D. M. Walker K.-H. Glassmeier |
| author_sort | P. T. I. Eriksson |
| collection | DOAJ |
| description | Three ULF wave events, all occurring in the dayside magnetopshere
during magnetically quiet times, are studied using the Cluster
satellites. The multi-point measurements obtained from Cluster are
used to determine the azimuthal wave number for the events by
means of the phase shift and the azimuthal separation between the
satellites. Also, the polarisation of the electric and magnetic
fields is examined in a field-aligned coordinate system, which, in
turn, gives the mode of the oscillations. The large-inclination
orbits of Cluster allow us to examine the phase relationship
between the electric and magnetic fields along the field lines.
The events studied have large azimuthal wave numbers (<i>m</i>~100),
two of them have eastward propagation and all are in the
poloidal mode, consistent with the large wave numbers. We also use
particle data from geosynchronous satellites to look for
signatures of proton injections, but none of the events show any
sign of enhanced proton flux. Thus, the drift-bounce resonance
instability seems unlikely to have played any part in the
excitation of these pulsations. As for the drift-mirror
instability we conclude that it would require an unreasonably high
plasma pressure for the instability criterion to be satisfied.<br><br><b>Keywords.</b> Ionosphere (Wave propagation) – Magnetospheric
physics (Plasma waves and instabilities; Instruments
and techniques) |
| first_indexed | 2024-04-13T20:31:20Z |
| format | Article |
| id | doaj.art-a455d5333bd84bc1b98a7a11d57fe075 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-04-13T20:31:20Z |
| publishDate | 2005-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-a455d5333bd84bc1b98a7a11d57fe0752022-12-22T02:31:10ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762005-10-01232679268610.5194/angeo-23-2679-2005Poloidal ULF oscillations in the dayside magnetosphere: a Cluster studyP. T. I. Eriksson0L. G. Blomberg1A. D. M. Walker2K.-H. Glassmeier3Alfvén Laboratory, Royal Institute of Technology, Stockholm, SwedenAlfvén Laboratory, Royal Institute of Technology, Stockholm, SwedenSchool of Pure and Applied Physics, University of KwaZulu-Natal, Durban, South AfricaInstitute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Braunschweig, GermanyThree ULF wave events, all occurring in the dayside magnetopshere during magnetically quiet times, are studied using the Cluster satellites. The multi-point measurements obtained from Cluster are used to determine the azimuthal wave number for the events by means of the phase shift and the azimuthal separation between the satellites. Also, the polarisation of the electric and magnetic fields is examined in a field-aligned coordinate system, which, in turn, gives the mode of the oscillations. The large-inclination orbits of Cluster allow us to examine the phase relationship between the electric and magnetic fields along the field lines. The events studied have large azimuthal wave numbers (<i>m</i>~100), two of them have eastward propagation and all are in the poloidal mode, consistent with the large wave numbers. We also use particle data from geosynchronous satellites to look for signatures of proton injections, but none of the events show any sign of enhanced proton flux. Thus, the drift-bounce resonance instability seems unlikely to have played any part in the excitation of these pulsations. As for the drift-mirror instability we conclude that it would require an unreasonably high plasma pressure for the instability criterion to be satisfied.<br><br><b>Keywords.</b> Ionosphere (Wave propagation) – Magnetospheric physics (Plasma waves and instabilities; Instruments and techniques)https://www.ann-geophys.net/23/2679/2005/angeo-23-2679-2005.pdf |
| spellingShingle | P. T. I. Eriksson L. G. Blomberg A. D. M. Walker K.-H. Glassmeier Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study Annales Geophysicae |
| title | Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study |
| title_full | Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study |
| title_fullStr | Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study |
| title_full_unstemmed | Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study |
| title_short | Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study |
| title_sort | poloidal ulf oscillations in the dayside magnetosphere a cluster study |
| url | https://www.ann-geophys.net/23/2679/2005/angeo-23-2679-2005.pdf |
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