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Title: Simultaneous Recordings of VHF Scintillation Occurrences over a Wide Range of Southern Latitudes
Authors: Hajkowicz, L A
Issue Date: Feb-1989
Publisher: NISCAIR-CSIR, India
Abstract: Scintillation studies have been conducted simultaneously at low latitude and auroral zone stations using amplitude data from the VHF beacon orbiting satellite transmissions at a frequency of 150 MHz. It is evident that a general rapid decrease in random scintillation level, from nighttime to daytime (the dawn period) during the years of sunspot maximum, is preserved over a wide range of sub-ionospheric latitudes (from about 20° to 70° south geom. lat.). The variations in the diurnal scintillation levels are similar over a wide range of latitudes. In general, nighttime maxima and daytime minima in scintillations are associated with similar variation in the level of auroral geomagnetic disturbances. Auroral scintillation activity shows a distinct seasonal pattern, with equinoctial maxima and solsticial minim, coinciding with a similar variation in the corresponding level of auroral magnetic K-index. The mid-latitude scintillation activity departs from this seasonal pattern: the principal maximum is observed during the summer solstice and the minimum during the vernal equinox. On a few occasions it was possible to discern in the auroral ionosphere the presence of regular, quasiperiodic (QP) scintillations; all QP scintillation events occurred at relatively high zenith angles equatorwards of an auroral station. This is in agreements with preferential direction of occurrence of the regular fading at lower latitudes. It is evident that strong random scintillations, extending from sub-auroral latitudes to the polar cap, can be present even during quiet geomagnetic conditions (K-index1); this is relatively unknown feature of the auroral scintillation morphology. It appears that the enhanced auroral scintillations of this type are associated with the occurrence of a specific type of sporadic-E, the so called constant-height sporadic-E (Esc), consisting of small-scale irregularities.
Page(s): 2-9
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.18(1) [February 1989]

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