UHF scintillation activity over polar latitudes

Abstract

Polar cap ionospheric irregularities have been monitored for several years from Thule Air Base, Greenland using 250 MHz satellite beacon scintillation measurements. The seasonal pattern of the polar cap irregularities shows very high intensity levels during the winter and lower levels during the summer (sunlit) months. This behavior is similar to in‐situ polar cap electric field measurements which show larger fluctuations in the winter than in the summer, an effect which may be related to E layer conductivity changes. A striking contrast was noted between high scintillation levels observed during 1979/80, a year of high solar flux, and much lower levels observed during 1975, a year of low solar flux. This variation may be related to a corresponding solar cycle variation in polar cap F layer electron density. The data reveal little difference between periods of high and low Kp, and only a weak diurnal variation in any season. Direct optical and ionosonde measurements indicate that these scintillations are produced by ionospheric irregularities in the polar cap F‐region. Results of spaced receiver drift measurements indicate that the small scale of irregularity drift was antisunward. Intense irregularities are associated with discrete sun aligned F layer auroras. A weak background level of scintillation persisted in the high solar flux years.

Phase scintillations at the polar ionosphere

“…Recent work in [7] over the period of solar minimum (2007)(2008) at two polar region stations at Ny-Ålesund, Svalbard (78.9°N, 11.9°E) and Larsemann Hill, East Antarctic (69.4°S, 76.4°E) concluded that phase scintillation and irregularities observed from GISTM receivers mainly takes place in October, November and December at NyÅlesund, and in May and June at Larsemann Hill. This is in agreement with the finding in [8].…”

Scintillation and In-situ Irregularity Parameters in the Auroral Oval and Polar Cap

“…The additional geo-stationary scintillation data from Tromso and Thule presented in Section 3 provide much new information when considered in tandem with earlier published work from Thule (Aarons et al, 1981), Goose Bay (Basu et al, 1988), and Narssarsuaq (Basu, 1975;Basu and Aarons, 1980). If we start with the Thule data which refers to the central polar cap, then we find that the UT seasonal and solar cycle dependence of scintillations are generally consistent with transport of plasma from sub-cusp latitudes taken in conjunction with the shorting effect of a sunlit E-region in the summer on F-region irregularities.…”

F layer ionization patches in the polar cap

“…However, uhf scintillation measurements, a measure of km-scale irregularities, do not show a strong dependence on the level of geomagnetic activity. Scintillation occurrence measured from Thule, Greenland (860 CGL), was shown by Aarons et al 8 to be essentially independent of K p. Thus, during disturbed geomagnetic periods, when structured particle precipitation into the polar cap does not directly produce the observed irregularities, transport of plasma and irregularities from other production regions must be considered.…”