|
|
 |
|
|
Ann. Geophys., 22, 3177-3193, 2004
www.ann-geophys.net/22/3177/2004/
© European Geosciences Union 2004
Equatorial ionospheric zonal drift model and vertical drift statistics from UHF scintillation measurements in South America
R. E. Sheehan and C. E. Valladares
Institute for Scientific Research, Boston College, Chestnut Hill, Massachusetts, USA
Abstract. UHF scintillation measurements of zonal ionospheric drifts have been
conducted at Ancon, Peru since 1994 using antennas spaced in the magnetic
east-west direction to cross-correlate geo-synchronous satellite signals. An
empirical model of average drift over a wide range of Kp and solar flux
conditions was constructed from successive two-dimensional fits of drift vs.
the parameters and day of year. The model exhibits the typical local time
trend of maximum eastward velocity in the early evening with a gradual
decrease and reversal in the early morning hours. As expected, velocities at
all hours increase with the solar flux and decrease with Kp activity. It was
also found that vertical drifts could contribute to the variability of drift
measurements to the east of Ancon at a low elevation angle. The vertical
drift at the ionospheric intersection to the east can be estimated when
combined with nearly overhead observations at Ancon or a similar
spaced-antenna site at Antofagasta, Chile. Comparisons on five days with
nearly simultaneous measurements of vertical drift by the Julia radar at
Jicamarca, Peru show varying agreement with the spaced-antenna estimates.
Statistical results from 1997 to 2001 generally agree with radar and
satellite studies.
Full Article in PDF (431 KB) |
|
|
