Abstract
Abstract. The climatological characteristics of UHF-band scintillations over the low-latitude region of China were investigated by analyzing the observations recorded at three stations of our regional network of satellite-beacon-based scintillation monitoring in 2013. The three stations are Hainan (geographic 20.0° N, 110.3° E; geomagnetic 10.1° N, 177.4° W, dip 28.2°), Guangzhou (geographic 23.0° N, 113.0° E; geomagnetic 13.1° N, 174.8° W, dip 33.9°) and Kunming (geographic 25.6° N, 103.7° E; geomagnetic 15.7° N, 176.4° E, dip 39.0°), located at low latitudes of China. The variations of UHF-band scintillation occurrence with latitude, time and season are presented in detail to understand the morphology and climatology of ionospheric scintillations over the low-latitude region of China. An equinoctial asymmetry in the occurrences of scintillation and an obvious difference of the onset time of scintillations between Hainan and Kunming is noted in this data set. Subsequently, the ionosonde data are utilized to study the possible causes of the asymmetry between two equinoxes. The observations suggest that the mean critical frequency (foF2) at 20:00 LT (12:00 UT) in the autumnal equinoctial months (September and October) and the vernal equinoctial months (March and April) has a similar asymmetry. The ratio of the mean foF2 between two equinoxes is proportional to the ratio between the maximum scintillation occurrence in the autumnal equinox and in the vernal equinox. Therefore, this ratio can act as a proxy for the equinoctial asymmetry in the occurrences of scintillation over the low-latitude region of China, and can be used to model the equinoctial asymmetry in our empirical climatological model of scintillation occurrence probability (CMSOP). The CMSOP can provide the predictions of the occurrences of scintillation over the low-latitude region of China and was validated in this study.
Highlights
Trans-ionospheric radio waves experience a rapid amplitude fading and phase jitter when they pass through electron density irregularities
The results suggest that the background F-region electron density may play an important role in the equinoctial asymmetry, and the FATVR can act as a proxy for the equinoctial asymmetry in the occurrences of scintillation over the low-latitude region of China, which can be used to model the equinoctial asymmetry in the climatological model of scintillation occurrence probability (CMSOP)
It is concluded that an equinoctial asymmetry in the percentage occurrences of scintillation exists over the low-latitude region of China
Summary
Trans-ionospheric radio waves experience a rapid amplitude fading and phase jitter when they pass through electron density irregularities. This phenomenon can be understood as multi-path inside the ionosphere, and this feature is referred to as ionospheric scintillation (Crane, 1977), which varies widely with frequency, time, season, latitude and solar and magnetic activity. The study of the climatology of scintillations for understanding and predicting scintillation activity is currently one of the major research topics in the space weather community. Over the past four decades, many studies on the scintillation theory, observations, morphological and climatological features have been published (e.g., Aarons, 1982, 1993; Yeh and Liu, 1982; Basu and Basu, 1985; Kil and Heelis, 1998; Nishioka et al, 2008; Sripathi et al, 2011).
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