SPINDEL: PHASE FLUCTUATIONS, COHERENCE AND INTERNAL VJAVES 



selected depths. We went out one convergence zone, using a frequency 

 of only 50 Hz because such computations are too expensive at 400 Hz. 

 A Bermuda-type profile was used over a high-loss bottom with a source 

 on the axis. Figure D-1 shows the transmission loss and phase 

 variations as a function of range. The phase has been de-meaned 

 over the 50-mile interval and the residual variations are plotted 

 in cycles. Note that in this case of axis-to-axis propagation, 

 the phase varies from linear only by about one quarter of a cycle. 

 But here is the propagation loss going along. I don't know if I 

 am willing to multiply it by 8 to scale it up to 400 Hz or not. 



One of the phase flip questions occurred to me when examining 

 the results near 22 nautical miles. There was a particularly deep 

 null in transmission loss, and the phase changes by nearly 180 

 degrees; actually, it is about 135 degrees. 



VJe ran this case again with very fine resolution in range and 

 the phase was totally continuous through there. There were no 

 discontinuities. I concede that if you are measuring the phase near 

 such a point, and the signal level has dipped down into noise there 

 is no way to track the phase. But there is no reason, no physical 

 reason, for the phase to be discontinuous. 



Figure D-2 corresponds to the same source but to receiver depth 

 of 300 feet. Here the phase and loss curves overlap. Note that the 

 phase-variation scale has been compressed to handle the 14-cycle 

 variation over the entire range. 



As you come up into the convergence zone, some fairly dramatic 

 things are happening in terms of phase. 



Figure D-3 is for a 1000-foot receiver depth where the up-and- 

 down-going convergence zones overlap more. Here the phase scale is 

 changed again. 



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