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Filamentary Alfvénic structures excited at the edges of equatorial plasma bubbles
Filamentary Alfvénic structures excited at the edges of equatorial plasma bubbles
- Source :
- Annales Geophysicae, Vol 25, Pp 2159-2165 (2007)
- Publication Year :
- 2007
- Publisher :
- Copernicus Publications, 2007.
-
Abstract
- Recent observations performed by the French DEMETER satellite at altitudes of about 710 km suggest that the generation of equatorial plasma bubbles correlates with the presence of filamentary structures of field aligned currents carried by Alfvén waves. These localized structures are located at the bubble edges. We study the dynamics of the equatorial plasma bubbles, taking into account that their motion is dictated by gravity driven and displacement currents. Ion-polarization currents appear to be crucial for the accurate description of the evolution of plasma bubbles in the high altitude ionosphere. During their eastward/westward motion the bubbles intersect gravity driven currents flowing transversely with respect to the background magnetic field. The circulation of these currents is prohibited by large density depressions located at the bubble edges acting as perfect insulators. As a result, in these localized regions the transverse currents have to be locally closed by field aligned currents. Such a physical process generates kinetic Alfvén waves which appear to be stationary in the plasma bubble reference frame. Using a two-dimensional model and "in situ" wave measurements on board the DEMETER spacecraft, we give estimates for the magnitude of the field aligned currents and the associated Alfvén fields.
- Subjects :
- Science
Physics
QC1-999
Geophysics. Cosmic physics
QC801-809
Subjects
Details
- Language :
- English
- ISSN :
- 09927689 and 14320576
- Volume :
- 25
- Database :
- Directory of Open Access Journals
- Journal :
- Annales Geophysicae
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.05a557cebbc9468ca81a7693f462cebf
- Document Type :
- article
- Full Text :
- https://doi.org/10.5194/angeo-25-2159-2007