Abstract
Abstract. In this paper, we examine ionospheric plasma depletions (or bubbles) and irregularities observed by photometers and a ground-based receiver of the global positioning system (GPS) both located in Brazil, South America. A simultaneous observation reveals that when the ionospheric plasma becomes depleted, the GPS total electron content decreases and the associated phase fluctuations grow. Statistical results show that the plasma bubbles and the significant GPS phase fluctuations generally occur during October-March. The solar activity variation is not obvious in either observation except during the equinoctial months. The GPS phase fluctuations suggest that the most pronounced ionospheric irregularities appear between 20:00 and 01:00 LT, which generally agree with previous ionospheric bubble observations.
Highlights
IntroductionOver the past two decades, observations of the satellite signals have been used to derive phase and amplitude scintillation at various latitudes (see the papers listed in Aarons, 1993)
Ionospheric plasma depletions often coexist with ionospheric irregularities in the equatorial regions (Kelley, 1989)
To further investigate ionospheric plasma bubbles and irregularities occurring in various solar activities, the longterm database of the photometer obtained at Cachoeira Paulista is compared with the global positioning system (GPS) phase fluctuations recorded at Brasilia
Summary
Over the past two decades, observations of the satellite signals have been used to derive phase and amplitude scintillation at various latitudes (see the papers listed in Aarons, 1993). The establishment of a Global Positioning System (GPS) provides an alternative way to investigate the ionospheric irregularities. Aarons et al (1997) used GPS phase fluctuation, which is practically the time variation of the total electron content (TEC), as an indicator of the occurrence of ionospheric irregularities to study the occurrence of irregularities during the storm periods of 1993–1995. Mendillo et al (2000) further developed two indices to quantitatively examine the GPS phase fluctuations in various months during 1995–1998. The overlapped coverage provides scientists with a good opportunity to understand the relationship between ionospheric plasma bubbles and irregularities over Brazil (see Fig. 1). The two long-term databases are employed to investigate the occurrence of ionospheric plasma bubbles and irregularities in various solar activities, seasons, and local times
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