Morphology of Phase and Intensity Scintillations in the Auroral Oval and Polar Cap

摘要

The first long-term measurements of phase scintillations at high latitudes from a quasi-stationary Air Force satellite at 250 MHz are reported. The scintillation magnitudes were higher during the vernal equinox than during the winter solstice. Data for 64-72 deg N showed a well ordered diurnal variation with a nighttime maximum and daytime minimum, whereas the data for 85-89 deg N showed no such ordering. The long-term northern data shows that the major variation in scintillation activity is annual with minimum scintillations observed in the local summer. In contrast to the pronounced annual variation, the dependence of overall scintillation activity on sunspot cycle is not greatly evident during 1979-1982 when the sunspot number varied approximately between 100 and 200. It was found that both could show phase scintillations of the order of 10 rad (with 82-s detrend period) even during magnetically quiet times. One such case study, is presented and second-order parameters as phase and intensity spectral strengths and slopes and intensity decorrelation times are discussed for this event at both stations. The use of geostationary satellite data shows the importance of enhanced magnetospheric convection velocities on the observation of large phase scintillation values at both sites. This underscores the need for incorporating irregularity dynamics in the currently static models of ionospheric scintillation.