Wind and temperature effects on F-region medium-scale gravity waves estimated using a multi-layer atmospheric model |
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| Institution: | 1. Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan;2. Institute of Space Science, National Central University, Jhongli 32001, Taiwan;1. Institut de Recherche en Astrophysique et Planétologie, CNRS-UPS-CNES, Toulouse, France;2. Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Japan;3. Laboratoire de Physique et Chimie de l’environment et l’espace, Université Orleans-CNRS, Orleans, France;1. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan;2. Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;3. RIKEN Advanced Institute for Computational Science, 7-1-26, Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan;1. Institute of Computational Modelling, Russian Academy of Sciences, Siberian Branch, 660036, Krasnoyarsk, Russia;2. Siberian Federal University, 79 Svobodny Prospect, 660041, Krasnoyarsk, Russia;3. Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042, Graz, Austria |
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| Abstract: | Diurnal variations in the propagation direction of atmospheric gravity waves, and the travelling ionospheric disturbances to which they give rise, have been observed in many experimental observations and several modelling studies have demonstrated that this is primarily due to the corresponding diurnal rotation in the direction of the thermospheric wind. Other variations have been attributed to seasonal or other effects, but the effects of variations in the thermospheric temperature have not previously been analysed in detail. We present results from a study of the propagation of gravity waves through a layered atmosphere in which the thermospheric wind and temperature are derived from a three-dimensional time-dependent model. The analysis has been carried out for a range of wave speeds and periods, and for a range of times, seasons and propagation azimuths. Results suggest that a significant diurnal variation in the transmission coefficient for waves propagating through the thermosphere exists with seasonally dependent maxima. Transmission increases for increasing wave period up to about 50 min, after which it remains approximately constant. Maximum transmission occurs for wave phase speeds around 200–250 m/s and falls to zero for speeds less than about 100 m/s. An exception to this rule occurs for waves with periods less than 40 min and speeds less than 50 m/s for which significant transmission appears to be theoretically possible. |
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