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Variation of the auroral oval size and offset for different magnetic activity levels described by the Kp‐index
Author(s) -
Wagner Daniel,
Neuhäuser Ralph
Publication year - 2019
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.201913601
Subject(s) - earth's magnetic field , radius , physics , offset (computer science) , geodesy , dusk , astrophysics , magnetic field , geology , astronomy , computer security , quantum mechanics , computer science , programming language
The understanding of the behavior of the auroral oval is crucial for the correct reconstruction of its size and location during past centuries by using historical aurora sightings. Therefore, we investigated the radius of the intensity maximum of the oval as well as the offset from the geomagnetic poles for different magnetic activity levels described by the Kp‐index. The Spin‐Scan Auroral Imager mounted on the Dynamics Explorer 1 satellite provides image data from 1981 to 1991, which were used for this purpose. Geometrical analysis of the oval's intensity maximum for each image, transformed into quasi‐dipole coordinates, gives the center of the oval and its radius. The results show a linear dependence between the Kp‐index and radius and a nearly constant shift of the oval center toward the midnight sector of around 4.5°. Furthermore, the images show that the Holzworth mathematical model underestimates the size of the auroral oval in the dawn and dusk sector especially for high magnetic activities.