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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 25, issue 8
Ann. Geophys., 25, 1767–1778, 2007
https://doi.org/10.5194/angeo-25-1767-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 25, 1767–1778, 2007
https://doi.org/10.5194/angeo-25-1767-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.

  29 Aug 2007

29 Aug 2007

The quasi-two-day wave studied using the Northern Hemisphere SuperDARN HF radars

S. B. Malinga1,* and J. M. Ruohoniemi2 S. B. Malinga and J. M. Ruohoniemi
  • 1School of Physics, University of KwaZulu-Natal, Durban 4000, South Africa
  • 2The Johns Hopkins University Applied Physics Laboratory, Laurel, MD20723, USA
  • *now at: Hermanus Magnetic Observatory, PO Box 32, Hermanus, 7200, South Africa

Abstract. Data from the Super Dual Radar Network (SuperDARN) radars for 2002 were used to study the behaviour of the quasi-two-day wave (QTDW) in the Northern Hemisphere auroral zone. The period of the QTDW is observed to vary in the range of ~42–56 h, with the most dominant period being ~48 h and secondary peaks at ~42- and ~52-h. The spectral power shows a seasonal variation with a peak power (max~70) in summer. The power shows variations of several days and there is also evidence of changes in wave strength with longitude. The 42-h and the 48-h components tend to be strongly correlated in summer. The onset of enhanced wave activity tends to coincide with the westward acceleration of the zonal mean flow and occurs at a time of strong southward meridional flow. The most frequent instantaneous hourly period is in the 40 to 50 h period band, in line with the simultaneous dominance of the 42-h and the 48-h components. The wave numbers are less variable and are around −2 to −4 during times of strong wave activity. For a period of ~48 h, the zonal wave number is about −3 to −4, using a negative value to indicate westward propagating waves. The 42-h and the 52-h components cover a wider band in the −4 to 1 range. The wide zonal wave number spectrum in our results may account for the observed longitudinal variation in the spectral power of the wave.

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