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Poster De Conférence Année : 2013

VLF saucers source region and generation revealed by the four Cluster satellites

A. Masson
  • Fonction : Auteur
J. S. Pickett
  • Fonction : Auteur
A. Fazakerley
  • Fonction : Auteur
C. Forsyth
  • Fonction : Auteur
H. E. Laakso
  • Fonction : Auteur
J.-L. Rauch
  • Fonction : Auteur
Pierrette Décréau
  • Fonction : Auteur
  • PersonId : 1011613

Résumé

A VLF saucer is a natural radio-wave phenomenon observed in the auroral zone since the 1960's. It has a characteristic V-shaped signature on electric field spectrograms in the VLF range. Many properties of VLF saucers have been established in the 1970's based on Alouette and Isis spacecraft. Further investigations continued thanks to satellites flying over the auroral zone, such as Viking, Polar and FAST. Since 2006, the orbits of the ESA/NASA Cluster satellites are slowly evolving from a nominal polar orbit to an oblique one. Meanwhile, the perigee of their orbits, originally at 19,000 km, naturally decreased to a few hundred kilometres and since 2011 have been steadily increasing back to the original perigee. Since spring 2009, Cluster scientists can make use of this natural orbital drift to target a new key region of the magnetosphere: the Auroral Acceleration Region (AAR). The AAR continues to be targeted by the Cluster mission, with a recent data campaign achieved successfully in Spring 2013. On rare occasions, VLF saucers are observed by the Cluster spacecraft, as they need to fly close enough to their source to catch them. Unique observations of electrostatic VLF saucers by the four Cluster satellites will be presented. These data not only enable for the first time to triangulate their source region, but they also allow revisiting some of the hypotheses commonly used so far in the analysis of their source region. Finally, the multi-point observations of VLF saucers question fundamental aspects of their generation. Indeed, it is difficult to understand, based on previously published studies, how transient structures such as electron holes are able to support the continuous generation of these electrostatic waves during several minutes, as observed by Cluster.
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Dates et versions

hal-02862100 , version 1 (09-06-2020)

Identifiants

  • HAL Id : hal-02862100 , version 1

Citer

A. Masson, Matthieu Berthomier, J. S. Pickett, A. Fazakerley, C. Forsyth, et al.. VLF saucers source region and generation revealed by the four Cluster satellites. American Geophysical Union, Fall Meeting, Dec 2013, San Francisco, California, United States. 11, pp.SM11B-2103, 2013. ⟨hal-02862100⟩
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