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Auroral E-region electron density gradients measured with EISCAT

Authors
  • Haldoupis, C.1
  • Schlegel, K.2
  • Hussey, G.3
  • 1 University of Crete, Physics Department, Iraklion, Greece , Iraklion
  • 2 Max-Planck Institut für Aeromonie, Katlenburg-Lindau, Germany , Katlenburg-Lindau
  • 3 University of Saskatchewan, Department of Physics and Engineering Physics, Canada
Type
Published Article
Journal
Annales Geophysicae
Publisher
Springer-Verlag
Publication Date
Sep 01, 2000
Volume
18
Issue
9
Pages
1172–1181
Identifiers
DOI: 10.1007/s00585-000-1172-x
Source
Springer Nature
Keywords
License
Yellow

Abstract

In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the ambient electron density gradients, ▽Ne, in the E-region plasma. In this work, we took advantage of the EISCAT CP1 data base and studied statistically the vertical electron density gradient length, Lz = Ne/(dNe/dz), at auroral E-region heights during both eastward and westward electrojet conditions and different ambient electric field levels. Overall, the prevailing electron density gradients, with Lz ranging from 4 to 7 km, are found to be located below 100 km, but to move steadily up in altitude as the electric field level increases. The steepest density gradients, with Lz possibly less than 3 km, occur near 110 km mostly in the eastward electrojet during times of strong electric fields. The results and their implications are examined and discussed in the frame of the linear gradient drift instability theory. Finally, it would be interesting to test the implications of the present results with a vertical radar interferometer.

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