Low-latitude scintillation occurrences around the equatorial anomaly crest over Indonesia

Abstract

Abstract. We investigated low-latitude ionospheric scintillation in Indonesia using two GPS receivers installed at Bandung (107.6 • E, 6.9 • S; magnetic latitude 17.5 • S) and Pontianak (109.3 • E, 0.02 • S; magnetic latitude 8.9 • S). This study aimed to characterise climatological and directional ionospheric scintillation occurrences, which are useful not only for the physics of ionospheric irregularities but also for practical use in GNSS (global navigation satellite system)-based navigation. We used the deployed instrument's amplitude scintillation (S4 index) data from 2009, 2010, and 2011; the yearly SSN (sunspot-smoothed numbers) were 3.1, 16.5, and 55.9, respectively. In summary, (1) scintillation occurrences in the post-sunset period (18:00-01:00 LT) during equinox months (plasma bubble season) at the two sites can be ascribed to the plasma bubble; (2) using directional analyses of the two sites, we found that the distribution of scintillation occurrences is generally concentrated between the two sites, indicating the average location of the EIA (equatorial ionisation anomaly) crest; (3) scintillation occurrence enhancements for the two sites in field-aligned directions are herein reported for the first time by ground-based observation in a low-latitude region; (4) distribution of scintillation occurrences at Pontianak are concentrated in the southern sky, especially in the southwest direction, which is very likely associated with the plasma bubble tilted westward with increasing latitude; and (5) scintillation occurrence in the post-midnight period in the non-plasma-bubble season is the most intriguing variable occurring between the two sites (i.e. post-midnight scintillations are observed more at Bandung than Pontianak). Most of the post-midnight scintillations observed at Bandung are concentrated in the northern sky, with low elevation angles. This might be due to the amplitude of irregularities in certain directions, which may be effectively enhanced by background density enhancement by the EIA and because satellite-receiver paths are longer in the EIA crest region and in a field-aligned direction.

Effects of pre-reversal enhancement of E × B drift on the latitudinal extension of plasma bubble in Southeast Asia

“…These latitudinal ranges in the Southeast Asia longitudinal sector correspond to the EIA crest region. Beniguel et al (2009) and Abadi et al (2014) have reported that strong scintillations were concentrated in EIA crest region. Since intensity of the amplitude scintillation is proportional to amplitude of the plasma density, the strong scintillations occur at the EIA crest region, where the plasma density is high.…”

“…Scintillation due to multipath frequently occurs at elevation angles less than 30°. We have excluded scintillation due to multipath, by applying the method of Abadi et al (2014), who have successfully excluded multipath-affected scintillation using the standard deviation of code-carrier divergence (sigmaCCDiv) measure. The other GPS receiver was installed at Kototabang (0.2°S, 100.3°E; 9.9°S magnetic latitude).…”

Shrinking equatorial plasma bubbles

“…Estimations show that it takes a few hours after sunrise to refill depleted flux tubes at altitudes greater than 700 km [Huang et al, 2013;Sidorova and Filippov, 2014]. There are many reports on scintillation and EPB measurements in the ionization anomaly crest regions around 15°magnetic latitudes [Immel et al, 2004;Lee et al, 2009;Candido et al, 2011;Abadi et al, 2014]. Only those EPBs that have grown to apex altitudes of 750 km and above over the dip equator can be observed at such latitudes.…”

Predawn plasma bubble cluster observed in Southeast Asia

“…The zonal space of 50 km was also reported from observations [ Kelley , ; Kudeki and Bhattacharyya , ; Hysell et al , , ; Rodrigues et al , ; and Kudeki et al , ]. Theoretically, the plasma bubble occurrence is high when the solar terminator is aligned with the geomagnetic field line [ Tsunoda , ], so that equinoxes are the active seasons for plasma bubbles [e.g., Otsuka et al , ; Yokoyama et al , ; Abadi et al , ]. The plasma density is extremely low inside the plasma bubble compared to that of outside, and the plasma boundary is very sharp.…”