On the signature of the quasi-3-day wave in the thermosphere during the January 2010 URSI World Day campaign

摘要

Ultra-fast Kelvin waves with periods of 3-5days are important in the coupling of the lower atmosphere to the thermosphere and ionosphere. Here we focus on the observations and effects of a 3-day wave during January 2010. As this time period coincides with a stratospheric warming event, a coordinated set of observations with incoherent scatter radars are available. While there is no evidence that the occurrence of this 3-day wave is connected with this event, these observations offer an unprecedented glimpse of the thermospheric conditions during this period, including the first-ever detection of a 3-day wave with an incoherent scatter radar. Using a combination of ground- and space-based observations, we identify an eastward moving zonal wave number-one 3-day equatorial wave that is comprised of a Kelvin wave at the lowest latitudes and a Rossby-gravity wave at higher latitudes. In the equatorial region, the vertical wavelength is ～40 km and the wave peaks in amplitude around 95-100km altitude. The wave observed here is only seen to propagate to around 105km altitude. Evidence of an interaction between this wave and the diurnal tide is seen between 82-88km. The resultant 3-day periodicity in the diurnal tide is seen to propagate up to altitudes of ～150 km. This could have a significant impact on the ionosphere via modulation of the E-region dynamo, thus carrying the 3-day periodicity to higher altitudes.