SINGLE-SCAN VELOCITY RESOLVER (VEEST)

VEEST computes velocities and magnetic field-aligned electron densities from elevation scans along the magnetic meridian, as a function of invariant latitude.

METHOD:

· Radar data from an elevation scan along the magnetic meridian are organized so that data at different altitudes are placed on the same field line. These data are then assigned an invariant latitude.
· The line-of-sight (l.o.s.) velocities in the F and E region are projected perpendicular to the magnetic field.
· At F-region altitudes (above about 180 km) the perpendicular l.o.s. component is considered to be ExB drifting and so this represents the north-south ion drift component, Vy. This component can then be directly related to the east-west electric field component, Ex
· At E-region altitudes the effects of ion collisions with neutrals is to reduce the ion speed and to rotate the ion velocity in the direction of the electric field. Thus, the north-south component of the electric field, Ey, is computed from F region and E region projected l.o.s. vectors accounting for the Hall and Pedersen mobility coefficients in the E region . The east-west component of the velocity,Vx, is computed from Ey

ASSUMPTIONS:

· Velocity along the magnetic field is zero
· E-region Neutral winds are negligible

SPATIAL COVERAGE:

· Determined by the extent of the E-region sampling. Maximum 4° invariant latitude

SPATIAL RESOLUTION:

· Governed by pulse length and scan rate. Typically 0.3°

TEMPORAL RESOLUTION:

· Determined by the time it takes to obtain an F region point and an E region point on the same field line. Typically 20 sec.