Morphology of phase and intensity scintillations in the auroral oval and polar cap

Abstract

The first long‐term measurements of phase scintillations at high latitudes from a quasi‐stationary Air Force satellite at 250 MHz are reported. The measurements were made from Goose Bay, Labrador covering the corrected geomagnetic latitude range of 64°–72°N and Thule, Greenland covering the corrected geomagnetic latitude range of 85°–89°N. Data from December 1979, March–April 1980 and March–April 1982 are presented from both stations. The sunspot numbers during these specific time periods were approximately the same. The scintillation magnitudes were higher during the vernal equinox at both stations than during the winter solstice. The Goose Bay data showed a well ordered diurnal variation with a nighttime maximum and daytime minimum, whereas the Thule data showed no such ordering. The limited phase scintillation data set from Thule is augmented by intensity scintillation measurements made during 1979–1982 using the same quasi‐stationary satellites. The long‐term Thule data shows that the major variation in scintillation activity is annual with minimum scintillations observed in the local summer, as was determined earlier by Aarons et al. (1981). 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 Goose Bay and Thule could show phase scintillations of the order of 10 rad (with 82‐s detrend period) even during magnetically quiet times. One such case study, conducted during March 1982, is presented and second‐order parameters such as phase aad 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 developed static models of ionospheric scintillation.