Journal cover Journal topic
Annales Geophysicae An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 1.490 IF 1.490
  • IF 5-year value: 1.445 IF 5-year
    1.445
  • CiteScore value: 2.9 CiteScore
    2.9
  • SNIP value: 0.789 SNIP 0.789
  • IPP value: 1.48 IPP 1.48
  • SJR value: 0.74 SJR 0.74
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 88 Scimago H
    index 88
  • h5-index value: 21 h5-index 21
Volume 23, issue 7
Ann. Geophys., 23, 2579–2588, 2005
https://doi.org/10.5194/angeo-23-2579-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 23, 2579–2588, 2005
https://doi.org/10.5194/angeo-23-2579-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  14 Oct 2005

14 Oct 2005

A statistical study of intense electric fields at 4−7 RE geocentric distance using Cluster

T. Johansson1, T. Karlsson1, G. Marklund1, S. Figueiredo1, P.-A. Lindqvist1, and S. Buchert2 T. Johansson et al.
  • 1Division of Plasma Physics, Alfvén Laboratory, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
  • 2Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden

Abstract. Intense high-latitude electric fields (>150 mV/m mapped to ionospheric altitude) at 4–7 RE geocentric distance have been investigated in a statistical study, using data from the Cluster satellites. The orbit of the Cluster satellites limits the data collection at these altitudes to high latitudes, including the poleward part of the auroral oval. The occurrence and distribution of the selected events have been used to characterize the intense electric fields and to investigate their dependance on parameters such as MLT, CGLat, altitude, and also Kp. Peaks in the local time distribution are found in the evening to morning sectors but also in the noon sector, corresponding to cusp events. The electric field intensities decrease with increasing latitude in the region investigated (above 60 CGLat). A dependence on geomagnetic activity is indicated since the probability of finding an event increases up to Kp=5–6. The scales sizes are in the range up to 10 km (mapped to ionospheric altitude) with a maximum around 4–5km, consistent with earlier findings at lower altitudes and Cluster event studies. The magnitudes of the electric fields are inversely proportional to the scale sizes. The type of electric field structure (convergent or divergent) is consistent with the FAC direction for a subset of events with electric field intensities in the range 500–1000 mV/m and with clear bipolar signatures. The FAC directions are also consistent with the Region 1 and NBZ current systems, the latter of which prevail only during northward IMF conditions. For scale sizes less than 2 km the majority of the events were divergent electric field structures. Both converging and diverging electric fields were found throughout the investigated altitude range (4–7 RE geocentric distance).

Keywords. Magnetospheric physics (Electric fields; Auroral phenomena; Magnetosphere-ionosphere interactions)

Publications Copernicus
Download
Citation