EGU21-866, updated on 09 Jan 2024
https://doi.org/10.5194/egusphere-egu21-866
EGU General Assembly 2021
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Elevation angles and attenuation of gravity waves in the ionosphere

Jaroslav Chum, Kateřina Podolska, Jiri Base, and Jan Rusz
Jaroslav Chum et al.
  • Institute of Atmospheric Physics, Upper Atmosphere, Prague 4, Czechia (jachu@ufa.cas.cz)

     Characteristics of gravity waves (GWs) are studied from multi-point and multi-frequency continuous Doppler sounding in the Czech Republic. Three dimensional (3D) phase velocities of GWs are determined from phase shifts between the signals reflecting from the ionosphere at different locations that are separated both vertically and horizontally; the reflection heights are determined by a nearby ionospheric sounder located in Průhonice. Wind-rest frame (intrinsic) velocities are calculated by subtracting the neutral wind velocities, obtained by HWM-14 wind model, from the observed GW velocities. In addition, attenuation of GWs with height was estimated from the amplitudes (Doppler shifts) observed at different altitudes. A statistical analysis was performed over two one-year periods: a) from July 2014 to June 2015 representing solar maximum b) from September 2018 to August 2019 representing solar minimum.   

     The results show that the distribution of elevation angles of wave vectors in the wind–rest frame is significantly narrower than in the Earth frame (observed elevations). Possible differences were also found between the wind–rest frame elevation angles obtained for the solar maximum (mean value (around -24°) and solar minimum (mean value round -37°). However, it is demonstrated that the elevation angles partly depended on the daytime and day of year. As the distribution of the time intervals suitable for the 3D analysis in the daytime–day of year plane was partly different for solar maximum and minimum, no reliable conclusion about the possible dependence of elevation angles on the solar activity can be drawn.

     It is shown that the attenuation of GWs in the ionosphere was in average smaller at the lower heights. This is consistent with the idea that mainly viscous damping and losses due to thermal conductivity are responsible for the attenuation.

  

How to cite: Chum, J., Podolska, K., Base, J., and Rusz, J.: Elevation angles and attenuation of gravity waves in the ionosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-866, https://doi.org/10.5194/egusphere-egu21-866, 2021.

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