Highly localized cooling in daytime mesopause temperature over the dip equator during counter electrojet events: First results

Abstract

The first observations of lowering of mesopause temperature during Counter Electrojet (CEJ) events over a narrow region of ∼ ±150 km centered at around magnetic equator are presented. The daytime mesopause temperature is measured over Trivandrum (8.5°N; 77°E; dip lat. 0.5°N), India using the ground based Multiwavelength Dayglow Photometer. The unique meridional scanning capability of the instrument is extensively used in this study. A lowering of temperature by as much as ∼25 K has been observed during certain CEJ events, which includes a few partial CEJs. The gravity wave tidal interaction through vertically upward wind is proposed to be manifesting as lowering in the mesopause temperature and also as CEJ. These observations are ‘new’ and address to the issues concerning the vertical coupling processes prevailing in the equatorial Mesosphere Lower Thermosphere Ionosphere (MLTI) region.

Equatorial counter electrojets and polar stratospheric sudden warmings – a classical example of high latitude-low latitude coupling?

“…In fact, it has already been shown earlier that the vertical wind associated with the upward propagating gravity waves in the dynamo region is very efficient in producing the CEJ over the dip equator Anandrao, 1980, 1987). In another study by Vineeth et al (2007b), the gravity wave associated vertical wind has been discussed and shown to be causing CEJs simultaneously with the localized cooling at mesopause region. During the SSWs in this context, the role of vertical wind associated with the gravity waves would be of consequence in causing the CEJs, primarily in the phases when tidal amplitudes get weakened owing to the ongoing PW-tidal interactions.…”

“…Recently Vineeth et al (2007b) have shown that the CEJs were associated with a cooling in the equatorial mesopause. The Gravity Wave (GW) associated vertical wind and the modifications of the tidal components were proposed for this observation.…”

Variabilities of mesospheric tides and equatorial electrojet strength during major stratospheric warming events

“…Goncharenko and Zhang (2008) observed that ion temperatures at a mid-latitude site during the stratospheric warming of January 2008 revealed alternating regions of cooling in a large altitude range (150-300 km) and warming in a narrow altitude band (120-140 km). Earlier, Vineeth et al (2007a) observed a cooling in the daytime mesopause temperature over Trivandrum at the time of CEJ events. They suggested that the gravity wave-tidal interactions in the MLT region along with the changes in chemistry could be a plausible mechanism for the simultaneous occurrence of CEJ and mesopause temperature lowering.…”

“…They suggested that the gravity wave-tidal interactions in the MLT region along with the changes in chemistry could be a plausible mechanism for the simultaneous occurrence of CEJ and mesopause temperature lowering. Vineeth et al (2007b) noted a 16-day planetary wave to be associated with the CEJ. Earlier, Sridharan et al (2002) noted ∼16-day variability in the afternoon CEJ strength.…”

A new insight into the vertical neutral-ion coupling between the mesopause and equatorial ionosphere F-region

“…For instance, Vineeth et al (2007a) have shown that the lower atmospheric forcing, like the gravity waves and tides, have significant manifestations in the equatorial electrojet. At the same time, the mesopause energetics responds to such forcings in the form of a lowering in the mesopause temperature simultaneous to the occurrence of counter electrojet (Vineeth et al, 2007b). By now, it is well understood that the investigation of the variability in the mesopause region vis-à-vis changes in the ionosphere can lead to a better understanding of the prevailing atmosphere-ionosphere coupling at any given time.…”