VHF scintillations and plasma drifts observed in southern Taiwan during the declining phase of solar cycle 24

• Published in: TAO : Terrestrial, atmospheric, and oceanic sciences Vol. 32; no. 4; pp. 553 - 560
• Main Authors: Mao, Ya-Chih, Lin, Cissi Y.
• Format: Journal Article
• Language: English
• Published: Taiwan 中華民國地球科學學會 01.08.2021; Chinese Geoscience Union (Taiwan); Springer
• Subjects: Drift; Ionosphere; Plasma; Plasma drift; Receivers & amplifiers; Satellite communications; Solar cycle; Temporal variations; Very high frequency sounding; Scintillation; Plasma drift; Equatorial ionization anomaly
• ISSN: 1017-0839; 2311-7680
• DOI: 10.3319/TAO.2021.09.16.02

Long-term observations of very high frequency (VHF) scintillations sounded at 244 MHz were conducted at one of the Scintillation Network Decision Aid (SCINDA) sites in Pingtung (22.6°N, 120.5°E; geomagnetic latitude 12.5°N), Taiwan, in 2015 - 2019, over the declining phase of solar cycle 24. Two VHF receivers are used to derive zonal drift velocity. The responses of S_4 indices, occurrences and east-west drifts are investigated with respect to local time, season, and solar activity. The results show that strong scintillations (S_4 ＞ 0.5) appear frequently at early nighttime at equinoxes during the high solar activity year of 2015, while weak scintillations (S_4: 0.2 - 0.5) occur often at early daytime and more frequently at early nighttime in summer without obvious correlation with solar activity levels. The peak drift of ~50 - 60 m s^(-1) is observed eastward at night and westward during the day. Stronger scintillations and higher drift velocities are observed in spring and fall.