MULTIPLE-SCAN VELOCITY RESOLVER

METHOD:

· Elevation scans along the magnetic meridian are bracketed by composite scans (combined azimuth and elevation angles) that provide measurements in planes parallel to the magnetic meridian but offset by about 100 km at F-region altitudes to the east and west . Elevation scans are directed N -> S and composite scans are directed S -> N.
· Ion drift velocities are resolved by combining line-of-sight (l.o.s.) measurements of ion velocity from elevation scans (E) and composite scans (C) within common altitude and invariant latitude bins. The process is applied to all data between 180 and 500 km altitude.
· Numerous combinations between scans are possible depending on temporal and spatial resolution constraints, as illustrated in the box.

ASSUMPTIONS:

· Everything ExB drifts from 180 km up
· Time invariance between line-of-sight pair measurements
· Flow is longitudinally uniform at the latitude of the line-of-sight pairs

SPATIAL RESOLUTION:

· Governed by pulse length, scan rate and orientation. Typically 0.2° in latitude, 100 km in longitude, 50 km in altitude
· 10° latitudinal coverage

TEMPORAL RESOLUTION:

· Maximum 45 sec. (at pairings where elscans end and compscans begin). Resolution of 4 min. for l.o.s. pairings at mid-point of scans. Lowest resolution 12 min