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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 28, issue 3
Ann. Geophys., 28, 807–815, 2010
https://doi.org/10.5194/angeo-28-807-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 28, 807–815, 2010
https://doi.org/10.5194/angeo-28-807-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  18 Mar 2010

18 Mar 2010

Daytime descending intermediate layers observed over a sub-tropical Indian station Waltair during low-solar activity period

K. Niranjan1,3, B. Srivani2, and V. V. S. Naidu1 K. Niranjan et al.
  • 1Department of Physics, Andhra University, Visakhapantam 530 003, India
  • 2Department of Physics, GITAM University Hyderabad campus, Hyderabad, India
  • 3Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan

Abstract. Study on daytime descending intermediate layer over subtropical Indian station Waltair (17.7° N, 83.3° E geographic, 6.4° N, 10° E geomagnetic, 20° N dip) located in the equatorial anomaly transition region, using an IPS 42 Digital Ionosonde during the low solar activity year 2004 showed that the layers occur in the altitude range of 140–160 km with maximum occurrence during winter solstice. The layers observed during daytime occur with a double peak variation throughout the year with less occurrence probability and shorter duration presence during forenoon hours. The morning layer descent was associated with a density increase where as during afternoon hours a decrease in density was observed. The downward drift velocity was about 8 km/h during morning hours and between 7–11 km/h during afternoon hours, with a low descent rate of around 4.5 km/h during summer morning hours. The results indicate the presence of a 6 h tide at this location as observed from the characteristics of the descending layers, unlike at majority of locations where a significant semi diurnal trend is observed. The study brings out the complex nature of the tidal interaction at different locations.

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