SPINDEL: PHASE FLUCTUATIONS, COHERENCE AND INTERNAL WAVES 



Dr. DeFerrari: No, the first one was measured and it probably 

 was 8 seconds. They are typically 8 to 10 seconds. 



Dr. Schulkin: It was measured? 



Dr. DeFerrari: Yes. The first set of a few. Yes. That is 

 what it looks like. The swell comes in very strong. The wind-driven 

 waves are much less compared to the real spectrum. I have done that 

 with surface data at the same time and compared the spectra and it 

 looks just about like the wave spectra, that the wind waves fall 

 out much more rapidly than the actual spectrum. 



I have also done it as a function of frequency and a number of 

 other things. 



Dr. R. M. Fitzgerald (Naval Research Laboratory) : I wanted to 

 make a quick comment on the physical nature of discontinuous phase 

 jumps. What we have is a physical field, a pressure field. When 

 you decompose that field into phase and amplitude, that is unphysical, 

 if you like. 



However, when the amplitude vanishes, the phase is not deter- 

 mined. So when the amplitude truly vanishes, the phase can change 

 discontinuously in the physical pressure field. 



Dr. T. G. Birdsall (Cooley Electronics Laboratory) : Some people 

 have had a lot of experience trying to read data through those 

 points, because it is the nastiest point in the world. The nicest 

 thing is to run three frequencies through it, you know, an epsilon 

 apart on either side — 



Mr. Spofford: 1 would argue in a deterministic physical model 

 like this that the amplitude probably cannot vanish. 



460 



