Evidence for the presence of turbulent attenuation on low-elevation angle Earth-space paths. 2. Frequency scaling of scintillation intensity on a 10/spl deg/ path

For pt.1 see ibid., vol.45, no.1, p.73-84 (1997). This paper presents the results of and conclusions drawn from two experimental studies of low-elevation, slant-path scintillation. Part I related to 11.2-GHz measurements at an elevation angle of 3.3/spl deg/. Part II describes 14- and 11-GHz observations made on a (nominal) 10/spl deg/ path over a four year period. The resulting time-series data have enabled frequency scaling to be investigated in some depth. Scintillation occurring during periods unassociated with fading is found to be well modeled in its frequency scaling behavior by classical theories of clear air turbulence (CAT). This is not the case, however, for scintillation that occurs during, just before, or just after rain-induced fading. A rapidly fluctuating attenuation mechanism, not separable from CAT-induced scintillation on the basis of its spectrum alone, is thought to be responsible for this anomalous frequency-scaling result.