Abstract:
This research reports on recently recorded 250 MHz amplitude scintillations at
Waltair (17.7°N, 83.3°E), a low-latitude station in India, using the signals radiated
from a geostationary satellite (FLEETSAT, 73°E) during a six-year period (2008 -
2013), which covers extremely low and higher solar activity years (2008 and 2013).
The morphological features in terms of local time, month, and season during different
geophysical conditions are presented. The scintillation patches (segregated based on
their occurrence durations) have shown an increasing trend with the increasing sunspot
activity. The scintillation patches with 30-min duration show increasing trends
with increasing sunspot activity, and their occurrence frequencies also show increasing
trends with increasing sunspot activity. The scintillation activity during disturbed
epochs (Kp index lies between 3+
and 9) is found to be less compared to its quiet day
counterparts. The plausible mechanisms for these observational results are discussed.
In addition, power spectral characteristics, including Fresnel frequency, upper role
of frequency and spectral slope of scintillations are calculated and the salient results
are presented.
