Millstone Hill incoherent scatter observations of exospheric temperature over 25 to 60 degrees north latitude

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Abstract
Elevation scan observations made by the Millstone Hill incoherent scatter radar are analyzed to produce local‐time/latitude maps of exospheric temperature. By lowering the antenna elevation to 4 degrees, observations in the thermosphere are possible over the latitude range 25 to 60 degrees north. These radar maps of exospheric temperature provide a new capability for the simultaneous monitoring of the detailed temporal and spatial morphology of the thermosphere. The combination of such maps from different radars promises to provide a powerful new tool for global thermospheric studies. The results for two multi‐day experimental periods in March and November 1982 are presented and described. During magnetically quiet periods the latitudinal variation of exospheric temperature is observed to be small in comparison with the diurnal variation. During disturbed periods large ion frictional heating events are observed at high latitudes and may extend even to mid latitudes during the more energetic events. These frictional heating effects upon the ions severely contaminate and exaggerate the deduced neutral temperatures. The second of the two November days showed substantially higher temperatures than the first even at mid and low latitudes. It is suggested that the high level of magnetic activity commencing on the prior evening and persisting for more than 24 hours served to generate an aurorally driven circulation cell that deposited auroral energy throughout the radar field of view.