Irregular structures observed below 71 km in the night-time polar D-region

Citation
Ev. Thrane et al., Irregular structures observed below 71 km in the night-time polar D-region, ANN GEOPH, 18(2), 2000, pp. 215-222
Citations number
16
Categorie Soggetti
Space Sciences
Journal title
ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES
ISSN journal
09927689 → ACNP
Volume
18
Issue
2
Year of publication
2000
Pages
215 - 222
Database
ISI
SICI code
0992-7689(200002)18:2<215:ISOB7K>2.0.ZU;2-2
Abstract
A new rocket range, SvalRak, was opened in November 1997 at Ny-Alesund (79 degrees N) in the Svalbard archipelago. The first instrumented rocket was l aunched on 20 November, 1997, at 1730 UT during geomagnetically quiet condi tions. The payload was instrumented to measure plasma parameters in the mes osphere and lower thermosphere, but the payload only reached an altitude of 71 km. This resulted in a very flat trajectory through the lower D-region. The positive ion concentrations were larger than expected, and some unexpe cted plasma irregularities were observed below 71 km. The irregularities we re typically 100 m in spatial extent, with plasma densities a factor of two to five above the ambient background. In the dark polar night the plasma b elow 71 km must consist mainly of positive and negative ions and the only c onceivable ionising radiation is a flux of energetic particles. Furthermore only relativistic electrons have the large energies and the small gyro rad ii required in order to explain the observed spatial structure. The source of these electrons is uncertain.