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The occurrence and properties of large-scale electron-density structures in the auroral F region

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • C. J. Burns
  • J. K. Hargreaves
<mark>Journal publication date</mark>01/1996
<mark>Journal</mark>Journal of Atmospheric and Terrestrial Physics
Issue number1-4
Number of pages16
Pages (from-to)217-232
Publication StatusPublished
<mark>Original language</mark>English


In order to investigate the cause of electron-content variations in the auroral zone, irregular structures in the auroral F region over EISCAT were observed during 12, 1.5-h runs of a special program in the years 1982–1986, and again during a 12-h run in October 1992. The paper presents statistical information about the occurrence, magnitude and height of the structures, and addresses some essential characteristics of individual blobs, such as motion and temperatures, which bear on the question of their origin. Blobs are classified according to their height. Types 1 and 2 correspond to the most intense fluctuations in electron content and occur between 250 and 400 km altitude. At the edge of a blob the temporal change in electron content can be as much as 1 × 1017 m−2 in 30 s, and the spatial change as much as 2 × 1017 m−2 over 10 km. The intensity of these blobs is higher during years of high solar activity and their temperatures indicate that they are not produced locally. Type 3 blobs occur below 250 km altitude and are found to be hotter than the surrounding plasma which suggests that they are more likely to have been created recently by local particle precipitation. A method of measuring the drift of blobs is demonstrated and results are compared with the plasma drift determined from tristatic measurements. The results indicate that the blobs drift with the plasma and at the same speed.