Observational evidence of non linear interaction between tides and planetary waves in the mesosphere and lower thermosphere over Tirunelveli (8.7oN, 77.8oE)
Abstract
Atmospheric tides in the low-latitude mesosphere and lower thermosphere (MLT) region show large variabilities with time scales of a few days to three weeks. It is of interest to know what causes these variabilities, as these variabilities are manifested to some extent in the equatorial ionospheric current system. One important mechanism for these variabilities is the non-linear interaction between planetary waves and tides, which produces several secondary waves including the sum and difference frequencies of the original components. Due to these interactions, the tides will get modulated at periods of interacting planetary waves. In the present work the MLT wind observations from the medium frequency (MF) radar over Tirunelveli (8.7oN, 77.8oE, 1.75oN dip) have been used to study the variabilities of tides in the context of non linear interaction with planetary waves. Three winter periods are studied of this work and it reveals the nonlinear interaction between diurnal tide and planetary waves with periods 16 days are stronger than those of semidiurnal tide and planetary waves. Similar wave modulation is observed in the equatorial electrojet strength over Tirunelvei, which is a station close to dip equator, indicating that tidal winds modulated at planetary wave periods play a significant role in the day-to-day variabilities of equatorial electrojet strength. Detailed analysis is being carried out and the results will be presented during the meeting.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39.1692S