Dynamics and Electrodynamics of the Equatorial Zone - The Earth's Ionosphere: Plasma Physics and Electrodynamics - page 110

UT

13 17 21 01 05 09 13

Jicamarca F-region drifts

23-24 March 1971

40

20

0

220

B z (GSM)

5
0

2 5

24-25 March 1971

2 40

20
0
20

B z (GSM)

5
0

2 5

08 12 16

Local time (75

20 24 04 08

8 W)

Figure 3.26a F-region vertical drifts measured over Jicamarca (corresponding to an east-
ward electric field component) and IMF data. Note that the large nighttime drift pertur-
bations are well correlated with southward and northward IMF changes. Quiet-time
patterns are shown by dashed lines. [After Fejer (1986). Reproduced with permission of
Terra Scientific Publishing Co.]

(e.g., if B z returned northward), the Region 2 currents exceed Region 1 and
the opposite equatorial perturbation exists. These conditions are illustrated in
Fig. 3.24b. This work has continued, as described by Scherliess and Fejer (1997)
and Fejer and Scherliess (1997).
Another mechanism that creates low-latitude electrodynamic changes is called
a disturbance dynamo. If auroral zone heating and momentum sources are suf-
ficiently strong, the low-latitude neutral atmospheric winds can also be affected.
In turn, these winds will create different electric field patterns through the usual
E- and F-region dynamo process. Unlike the virtually instantaneous changes
shown previously, the disturbance dynamo takes more time to develop and
lags the auroral inputs by many hours. Gravity waves can also be generated by
high-latitude processes and propagate to low latitudes. It seems likely that the
wind fields associated with gravity waves will also create dynamo electric fields