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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 2
Ann. Geophys., 21, 481–492, 2003
https://doi.org/10.5194/angeo-21-481-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 21, 481–492, 2003
https://doi.org/10.5194/angeo-21-481-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.

  28 Feb 2003

28 Feb 2003

VLF emission triggering by a highly anisotropic energetic electron plasma

D. Nunn1, A. Demekhov2, V. Trakhtengerts2, and M. J. Rycroft3 D. Nunn et al.
  • 1Dept of Electronics and Computer Science, Southampton University, Southampton ,Hants SO17 1BJ, UK
  • 2Institute of Applied Physics, 46 Ulyanov St., Nizhni Novgorod 603600, Russia
  • 3CAESAR Consultancy , 35 Millington Rd, Cambridge CB3 9HW, UK and Faculty of Computing and Engineering Sciences,D e Montfort University, Leicester LE1 9BH, UK

Abstract. One of the objectives of the Cluster mission is to study sources of various electromagnetic waves using the four satellites. This paper describes the methods we have applied to data recorded from the STAFF spectrum analyser. This instrument provides the cross spectral matrix of three magnetic and two electric field components. This spectral matrix is analysed to determine, for each satellite, the direction of the wave normal relative to the Earth’s magnetic field as a function of frequency and of time. Due to the Cluster orbit, chorus emissions are often observed close to perigee, and the data analysis determines the direction of these waves. Three events observed during different levels of magnetic activity are reported. It is shown that the component of the Poynting vector parallel to the magnetic field changes its sense when the satellites cross the magnetic equator, which indicates that the chorus waves propagate away from the equator. Detailed analysis indicates that the source is located in close vicinity of the plane of the geomagnetic equator.

Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms); Space plasma physics (waves and instabilities)

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