First observations of SBAS/WAAS scintillations: Using collocated scintillation measurements and all-sky images to study equatorial plasma bubbles

The first observations of amplitude scintillations on a Space Based Augmentation System (SBAS) satellite signal are presented. The scintillations occurred on the signal transmitted by a Wide Area Augmentation Satellite (WAAS) on 8-9 September 2004 from 2250-0045 LT. The GPS receiver that measured the scintillations is located on Haleakala, Hawaii (geomagnetic: 21.3°N, 271.4°E). With a maximum S₄ = 0.35, corresponding to a peak-to-peak SNR variation of 8 dB, the scintillations are relatively weak, which is to be expected for a site poleward of the equatorial anomaly during declining solar conditions. Using a collocated all-sky imager, features of the irregularity structuring in the equatorial plasma bubbles are resolved. The satellite signals scintillate when the ray path intersects the three main bubbles. The scintillation intensity tends to peak near the walls, and decreases slightly in the interior of the bubbles. In this case, the bubbles' leading (east) walls contain smaller-scale-size irregularities than the trailing (west) walls.