Using phase scintillation spectral measurements to determine angle-of-arrival fluctuations during solar superior conjunction
Article first published online: 25 MAY 2010
Copyright 2010 by the American Geophysical Union.
Volume 45, Issue 3, June 2010
How to Cite
2010), Using phase scintillation spectral measurements to determine angle-of-arrival fluctuations during solar superior conjunction, Radio Sci., 45, RS3005, doi:10.1029/2009RS004176., , and (
- Issue published online: 25 MAY 2010
- Article first published online: 25 MAY 2010
- Manuscript Accepted: 2 FEB 2010
- Manuscript Revised: 22 SEP 2009
- Manuscript Received: 12 MAR 2009
- scintillation spectrum;
- angle-of-arrival fluctuations;
- solar conjunction
 In this study, we develop a complete theoretical approach to derive the angle-of-arrival fluctuations (AAF) of radio signals passing through the turbulent solar plasma medium during solar superior conjunctions. Using the power spectra of phase fluctuations measured at various solar elongation angles (or impact heliocentric distances) from the Cassini spacecraft, we have defined the dependence of the AAF variance on the heliocentric distance as ∼r−3.5 within a range very close to the Sun. This quantity decreases with increasing distance, with a slope significantly less steep than that previously expected. The AAF expression is theoretically derived by assuming a frozen turbulence and by converting a phase temporal variation into a spatial variation. To perform this calculation, the solar plasma medium is treated as an anisotropic ionized medium by applying the Booker electron irregularity spectrum model and the phase expression in term of the electron refractive index. Using the phase spectral measurements from the Cassini spacecraft during a solar superior conjunction, coefficients of the expression are calibrated, and the final AAF results are quantitatively obtained.