Optical and Radar Observations of the Midnight Temperature Maximum

An interesting phenomenon called the midnight temperature maximum (MTM) has been observed by Fabry-Perot measurements on numerous occasions over many years for low and equatorial latitudes. The MTM is seen near midnight and its amplitude is strongest during the equinox. We report on simultaneous optical and radar observations of the MTM that were obtained with Fabry-Perot and incoherent scatter radar measurements at Arecibo in Puerto Rico and at Arequipa-Lima in southern Peru. These results show that the heating represented by the MTM occur at altitudes above 270 km and is distributed evenly over the altitude range of 300 to 400 km.