Analysis Methods Used and the importance of proper interpretation of velocity deviations
Digisonde Drift Analysis (DDA) calculates
a 3-D velocity vector using the assumption of spatial uniformity. (Common technique used for velocity calculations.) [Inconsistent]
Generalized Digisonde Drift Analysis (GDDA) uses combination analysis to calculate the full velocity field distribution. Given a set of N
“sources”, and selecting r at a time to calculate
a velocity, NCr velocities are calculated.
Combination of sources from a dominant plasma motion would produce similar velocities, while combinations of sources from
different plasma motions would result in random motions. The resultant distribution would map out a velocity field. [Consistent]