In order to understand the evolution of equatorial spread F structures and their dynamics an investigation was carried out with the perturbation consisting of a single wavelength mode and superposition of two modes. The investigation revealed that the depleted region always moves upward with a single wavelength mode, while the superposition of two modes gives rise to low-level plasma depletion which moves downward even when the the ambient plasma motion is upward, in addition to well-developed upward moving plasma bubbles and downdrafting enhancements with varying degrees of development. Further, the evolution of well-developed plasma bubbles with scale size corresponding to a shorter-wavelength mode is possible even with very small (0.5%) amplitude of perturbation when it rides over a long-wavelength mode with large (5%) amplitude of perturbation. The longer-wavelength mode develops to form a lower envelope over which multiple plumes with varying degree of depletions ride, with the separation between the plumes decided by the short-wavelength perturbation subject to the amplitude of the former being larger in comparison with the latter. The rising multiple plumes and the descending structure along with a downward moving streak as observed by the Indian Mesosphere-Stratosphere-Troposphere (VHF) radar can qualitatively be understood on the basis of the interaction between the two modes which gives rise to depletions with varying growth rates and a rapidly descending enhancement followed by a downward moving weakly depleted region depending upon the wave parameters of the two modes.
If you can't find a tool you're looking for, please click the link at the top of the page to "Go to old article view". Alternatively, view our Knowledge Base articles for additional help. Your feedback is important to us, so please let us know if you have comments or ideas for improvement.