COMPARISON OF SATELLITE ELECTRON-DENSITY AND TEMPERATURE-MEASUREMENTSAT LOW LATITUDES WITH A PLASMASPHERE-IONOSPHERE MODEL

Observations made by the Hinotori satellite of the latitude and diurna l variations of electron density and temperature near 600 km altitude in the low-latitude region are studied by comparison with values from the Sheffield University plasmasphere-ionosphere model (SUPIM). The mo del results show that the observed features of higher electron density in the summer hemisphere and higher electron temperature in the winte r hemisphere are caused principally by the difference in the summer an d winter hemisphere values of the meridional neutral wind. Closer agre ement between the modeled and observed values is obtained when the int erhemisphere difference in the meridional wind, as given by the horizo ntal wind model (HWM) 90, is reduced and when the peak value of the da ytime poleward wind is moved to the afternoon sector in the winter hem isphere and to the morning sector in the summer hemisphere. The model results also show that the altitude variation of the vertical ExB drif t velocity plays an important role in the development of the ionospher ic equatorial anomaly. The latitude and diurnal variations of the mode led electron density and temperature are in good agreement with the ob servations when the ExB drift velocity used by the model is in accord with the observations made by the AE-E satellite for magnetic field li nes with apex altitude less than 400 km and at Arecibo for magnetic fi eld lines with apex altitude greater than 2000 km; linear interpolatio n of the observed values is used for the intermediate magnetic field l ines.