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Ground magnetic effects of the equatorial electrojet simulated by the TIE-GCM driven by TIMED satellite data

Research output: Contribution to journalJournal article

  • Yosuke Yamazaki
  • A.D. Richmond
  • A. Maute
  • Q. Wu
  • D.A. Ortland
  • A. Yoshikawa
  • I.A. Adimula
  • B. Rabiu
  • M. Kunitake
  • T. Tsugawa
<mark>Journal publication date</mark>04/2014
<mark>Journal</mark>Journal of Geophysical Research: Space Physics
Issue number4
Number of pages12
Pages (from-to)3150-3161
Early online date16/04/14
<mark>Original language</mark>English


Quiet-time daily variations of the geomagnetic field near the magnetic equator due to the equatorial electrojet are simulated using the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere Electro- dynamics General Circulation Model (TIE-GCM), and compared to those observed by ground-based magnetometers. Simulations are run both with and without tidal forcing at the height of the model lower boundary (∼97 km). When the lower-boundary forcing is off, the wind that generates an electro- motive force in the model is primarily the vertically non-propagating diurnal tide, which is excited in the thermosphere due to daytime solar ultra-violet heating. The lower-boundary tidal forcing adds the effect of upward-propagating tides, which are excited in the lower atmosphere and propagate vertically to the thermosphere. The main objective of this study is to evaluate the relative importance of these thermospherically-generated tides and upward-propagating tides in the generation of the equatorial electrojet. Fairly good agreement is obtained between model and observations when the model is forced by realistic lower-boundary tides based on temperature and wind measurements from the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite, as determined by Wu et al. [2012]. The simulation results show that the effect of upward-propagating tides increases the range of the geomagnetic daily variation in the magnetic-northward component at the magnetic equator approximately by 100%. It is also shown that the well-known semiannual change in the daily variation is mostly due to upward-propagating tides, especially the migrating semidiurnal tide. These results indicate that upward-propagating tides play a substantial role in producing the equatorial electrojet and its seasonal variability.

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