Dynamics and Electrodynamics of the Equatorial Zone - The Earth's Ionosphere: Plasma Physics and Electrodynamics - page 87

1000

100 m/s

900

V
⊥

Vertical

Chamical, Nov. 73

800

(projected to equator)

V ⊥ East

Chamical, Nov. 72

700

600

500 Natal,

Nov. 73

400

Punta Lobos,
March 79

300

200

Thumba, March 68

100

0
17:00 18:00 19:00 20:00

Local time

(a)

Jicamarca 25 Jan 1980

20:25

19:50 20:13 20:34

550

500

450

400

350

250 050 250 0 50

Eastward velocity (m/sec)

250 0 50 250 0 50

(b)

Figure 3.12 (a) Summary plot of plasma velocity derived from a number of barium ion
cloud experiments in the equatorial zone. The arrows show the electric field direction.
[After Fejer (1981). Reproduced with permission of Pergamon Press.] (b) Zonal drifts of
plasma irregularities as a function of height and time using an interferometric technique.
Note that the shear point where the velocity is zero moves up as the scattering layer rises.
[After Kudeki et al. (1981). Reproduced with permission of the American Geophysical
Union.]

altitude profiles of the eastward irregularity velocity are plotted in Fig. 3.12b.
The plasma velocities plotted here also change sign with height in agreement
with the results from the barium experiments.
A possible explanation for the shear is a variation on the shorting effect just
discussed. If the off-equatorial E-region dynamo creates ameridional electric field
that is in the poleward direction, and if the E-region dynamo internal resistance
is small enough, then the electric field will map to the equatorial plane as a