Counter equatorial electrojet: Analysis of the variability in daytime mesopause temperature and winds

This paper reports the variation of the daytime zonal wind and OH temperature at upper mesospheric altitudes during the afternoon equatorial counter electrojet (CEJ) events over a geomagnetic dip equatorial station, Trivandrum (8.5 degrees N, 77 degrees E, 0.5 degrees N diplat.), in India. The OH temperature is estimated using a unique Multiwavelength Dayglow Photometer and the zonal wind is obtained from a co-located Meteor Wind Radar. The CEJ events are identified by taking the difference between the surface magnetic field measurements of Trivandrum and Alibag (18.3 degrees N, 72.6 degrees E, 10.2 degrees N diplat.), obtained using two Proton Precession Magnetometers. Two major features were observed associated with the CEJ events: (i) an eastward increase in the zonal wind at 98 km altitudes and (ii) a clear-cut cooling in the mesopause, which in turn is proportional to the extent of the magnetic field reversal. These results are discussed in terms of the role played by the neutral winds, upward propagating gravity waves and the changes in the mesospheric chemistry. (C) 2011 Elsevier Ltd. All rights reserved.